# DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o?



## MikeWire (Oct 20, 2003)

*DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…*

DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…
Ok, so if you notice that you are loosing coolant and you are seeing a small puddle of coolant in your regular parking spot, you may have a coolant leak. It turns out my problem was the infamous drivers side coolant flange leak. 
Symptoms:
(please excuse the filthy engine bay)
1.	Red crusty residue near the transmission on the underside of the car:









2.	Red crusty residue on the drivers side between the coolant flange and the engine block:









If you experience any of these symptoms you may have a leaky coolant flange.
Here are the steps I took to remedy the problem:
DISCLAIMER: This DIY is for a MKIV Jetta 2.o, and may be similar to other makes/models. This information only a guide and if you screw up do not blame me – I will not be held responsible for any mistake you do while you work on your car. 
Hardware:
•	Meyle coolant flange 
• 1 gallon of Pentosin G12
•	Distilled Water
•	10mm socket
•	Gasket sealer (optional)
•	Flathead screwdriver
•	Paper towels
*Notes: Get the OEM VW coolant flange- I noticed the OEM is much stronger and seals better than the aftermarket replacement. I got mine from my service shop for around $20. If you don't get the OEM part, you will be doing this again!!!*
1.	Drain your coolant. I blocked and raised the drivers side of the car a drained all of the old coolant into an old milk carton. It's not necessary to remove all the coolant, but you should drain a majority - it makes much less of a mess. And, don't reuse the coolant - please recycle it:
Raise vehicle and block the wheels:








Remove the coolant reservoir cap on the expansion tank to release the vacuum in the cooling system: 








Using the coolant drain valve located on the underside of the radiator on the drivers side drain the coolant. *Again, it's not necessary to remove all the coolant, but you should drain a majority*:
















2.	Remove the engine cover (if applicable), remove your air box and the tubing that connects it to the throttle body and set it to the side. 








3.	Locate the coolant flange: 








4.	Begin by removing all the wiring, connectors and small hoses from around the flange. To make this easier I disconnected and removed the metal bracket from the top of the block _this is optional_:








5.	Remove all the hoses from the coolant flange. There are three hoses that connect to the flange and they all need to be removed. It doesn’t matter in what order, but be prepared to have some coolant drain out because there will be some left over in the block and hoses. I used a pair of channel lock pliers to loosen and move the spring clamps and they slip off fairly easily. 








6.	Now you can remove the flange from the block by removing the two nuts, then the bolts holding the flange in place. There is one nut and one bolt _behind the nut_ holding the flange in place. Using a 10mm socket, remove the bottom bolt: 








The top nut is bolted on to a stud that screws into the block. Remove the nut but leave the stud in place:








7.	You can then pull up on the black metal tubing (it will swing up towards the front of the car) and get to the bolt behind it. Once you remove bolt you can then remove the flange from the block. Make sure to clean up the dried up coolant and the surface of the block where the flange mounts.
TIP:

_Quote, originally posted by *leokempf* »_OK. figured it out. I didn't realize it would pivot all the way over at the thermostat housing. Forward of the "bar" I loosened a nut pretty far down in there that holds a bracket for some wires. Then I gave the bar a tug and it pivoted. Thanks.









8.	Now get the new flange and swap out the coolant sensor and O-ring.
Old VS. New:








Coolant flange part # from ECSTuning:
*See my notes above step 1 about using an OEM part*








Remove clip and O-ring from the old flange:
























Replace clip and O-ring and insert it into the new coolant flange:
NOTE: Now would be a good time to replace that black top coolant sensor with the new green top. I did not replace mine as I have had no problems with it.

























9.	Prep your new coolant flange (optional). This is probably unnecessary, but I used a high temp copper gasket sealant to make sure the flange will not leak again.








10.	Place your new coolant flange into the block:








11.	Replace the bolt and nut to secure the flange – be careful not to over tighten! 
* NOTE: Thanks to TMTuned99.5Golf: bolt torque is 7ft/lbs or 10* Nm
12.	Continue to replace all hoses, making sure to get the spring clamps back into the original place. Then replace the metal bracket and all wiring, connectors and small hoses.








13.	Time to add coolant – NOTE: Remember to close the drain valve on the underside of the radiator, or you will drain the coolant you are about to put in. Mix 50/50 Pentosin G12 and Distilled water and fill the coolant reservoir. Start the car and turn the cabin temperature knob to full HOT and turn the blower to HIGH and let the car warm up while you continue to fill the coolant reservoir. Fill until the expansion tank is filled to just above the midpoint of the container. Coolant temp should reach the 190 degree point. You may have to replace the expansion tank cap for the coolant pressure to build – then just top it off as needed.
14.	Replace the engine cover and test drive – you have just finished replacing your coolant flange!
NOTE: You may find that you need to check the level over the next few weeks to make sure the coolant level is at the correct level – based from my experience this seems normal and I have had no problems with my cooling system.









If anyone would like to add to this DIY please IM me – and if you have any questions please feel free to contact me. Thanks!


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## FaelinGL (Nov 28, 2004)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (mross71)*

Excellent DIY. I would recommend using some arrows to amplify the places you are talking about, but great shots. Lot of 2.slow engines out there so lots of people could use this. http://****************.com/smile/emthup.gif 
Mike


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## FaelinGL (Nov 28, 2004)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (mross71)*

Bump for the Daystaff crowd.
Mike


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## MikeWire (Oct 20, 2003)

New pics with arrows etc added...thx


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## digraph (Jul 23, 1999)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (FaelinGL)*

v.nice!
what does the stop-sticker on your air filter box say?


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## MikeWire (Oct 20, 2003)

It's a sticker that comes with a K&N drop in filter basically telling am oblivious service person that this is not a throw-away filter - so STOP don't throw it away. I do all my own work, but if I ever have to take it to a shop it may save my K&N...maybe.


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## MikeWire (Oct 20, 2003)

Bump for other 2.o owners


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## TMTuned99.5Golf (Jan 27, 2004)

*Re: (mross71)*

Heh, I just replaced mine this past weekend. Took me like an hour taking my time. Replaced before in the quickest time of like 15min.








BTW, if I'm not mistaken, the torque on those bolts that hold it down are like 7 ft/lbs ( 10 Nm ). 



_Modified by TMTuned99.5Golf at 7:34 PM 12-11-2006_


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## McNeil (Jan 18, 2006)

I vote for stickiness.


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## vwman099 (Sep 27, 2002)

*Re: (McNeil)*

bah... those flanges leak in the mkIV ABAs as well? that bites
thanks for the DIY


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## doodpod (Apr 27, 2004)

*Re: (vwman099)*

Great DIY, and a good heads up - I've been down on coolant and had yet to think of this problem. For reference though, the flange bolts to the head, not the block.


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## vasillalov (Nov 5, 2003)

*Re: (doodpod)*

Good work! http://****************.com/smile/emthup.gif


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## MikeWire (Oct 20, 2003)

*Re: (doodpod)*


_Quote, originally posted by *doodpod* »_Great DIY, and a good heads up - I've been down on coolant and had yet to think of this problem. For reference though, the flange bolts to the head, not the block.

You are correct is it the head, not the block. Noted and changed! Thank you!


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## MikeWire (Oct 20, 2003)

*Re: (TMTuned99.5Golf)*


_Quote, originally posted by *TMTuned99.5Golf* »_
BTW, if I'm not mistaken, the torque on those bolts that hold it down are like 7 ft/lbs ( 10 Nm ). 

Added! Thank You!


_Modified by mross71 at 10:30 AM 9-4-2007_


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## mujjuman (Jul 29, 2004)

*Re: (mross71)*

w00t thanks for the DIY dude! http://****************.com/smile/emthup.gif


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## MikeWire (Oct 20, 2003)

Thanks - hoping to get this into the DIY section


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## vasillalov (Nov 5, 2003)

*Re: (mross71)*

... let me see what I can do...


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## LangsamKafer (Jul 17, 2001)

Added to the DIY http://****************.com/smile/emthup.gif


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## MikeWire (Oct 20, 2003)

Thanks! I bow to vasillalov - king of DIY


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## mujjuman (Jul 29, 2004)

*Re: (LangsamKafer)*


_Quote, originally posted by *LangsamKafer* »_Added to the DIY http://****************.com/smile/emthup.gif

kool


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## Athfar (May 10, 2006)

*Re: (mujjuman)*

Hey found your post... How much did your flange cost when you did that?


_Modified by Athfar at 5:50 PM 1-6-2007_


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## 98wolfie (Jun 1, 2002)

*Re: (Athfar)*

I paid $15 in parts from the dealership. There doesn't seem to be much of a difference between the dealer price and online stores such as Potterman's and Germanautoparts.


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## Athfar (May 10, 2006)

*Re: (98wolfie)*

ECSTurning has the flange for like 8.95







http://ecstuning.com/stage/edp...oling


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## Athfar (May 10, 2006)

*Re: (Athfar)*









I wouldn't recommend putting that gasket sealant on there for three reasons.
1) It isn't really the seal that fails it is the composite / plastic underneath in my case. It ends up melting and deforming the plastic which just happens to take the seal along with it.
2) The type of gasket sealant you are using isn't designed for these types of press on rubber seals and in some cases can make the seal work less efficiently by gumming it up.
3) You are just making it harder to take off the next go around.
Thank you very much for the DIY. Just some more advice.















Oh, and one more tip for you guys doing this. If you look at the 10th picture down there is a black bar. You are unbolting the top nut from that piece (then you can move it up, have someone hold it up or undo the hose attached to it). After that unbolt the BOLT that is bolted into the engine.
The bottom bolt is the easy one because there isn't the bar in the way and if I recall it's just a single BOLT. This kinda confused me so I just though I should clarify.


_Modified by Athfar at 2:39 AM 2-1-2007_


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## dark-hour (Jul 5, 2007)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (mross71)*

I hope it is ok that I replied to this post. I have used VW vortex for many years. The amount of info is amazing. I have never really needed to post a question before. My question is more for a sanity check.
For about a week I have been loosing coolant. I notice coolant trickling over the coolant flange (Running around the temp. control sensor." 
My guess this is the coolant flange. Other then a hose is there anything else that could be causing the leak in this area? I have done a few searches on the forum, and am having problems narrowing down more information. 
Thanks guys
Kirk
2001 Jetta 2.0L


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (dark-hour)*


_Quote, originally posted by *dark-hour* »_
I hope it is ok that I replied to this post. I have used VW vortex for many years. The amount of info is amazing. I have never really needed to post a question before. My question is more for a sanity check.
For about a week I have been loosing coolant. I notice coolant trickling over the coolant flange (Running around the temp. control sensor." 
My guess this is the coolant flange. Other then a hose is there anything else that could be causing the leak in this area? I have done a few searches on the forum, and am having problems narrowing down more information. 
Thanks guys
Kirk
2001 Jetta 2.0L


Mine didn't take much to break the seal - I remember undoing hoses to drain coolant and change my timing belt and after that it started leaking. I figure the movement from pulling the hoses made the seal break.

_Quote, originally posted by *Athfar* »_
I wouldn't recommend putting that gasket sealant on there for three reasons.
1) It isn't really the seal that fails it is the composite / plastic underneath in my case. It ends up melting and deforming the plastic which just happens to take the seal along with it.


Mine didn't melt, the seal just failed...
Hm...well there are always two schools with the gasket sealant. My school is to use it sparingly. Other get into trouble where too much is used and it squishes into areas it shouldn't be and clogs things up. Others use none and then end of leaking anyway, doing the job twice as often.

_Quote, originally posted by *Athfar* »_
2) The type of gasket sealant you are using isn't designed for these types of press on rubber seals and in some cases can make the seal work less efficiently by gumming it up.


I use a high temp copper gasket sealer. I've used it on other vehicles and motorcycles with no ill effect and none have leaked after service. So, I at least speak from my experience, maybe yours was different. 

_Quote, originally posted by *Athfar* »_
3) You are just making it harder to take off the next go around.


?? Not even sure what you mean here...it's pretty easy to get gasket material off of a metal surface. And the flange is throw-away.

_Quote, originally posted by *Athfar* »_
Thank you very much for the DIY. Just some more advice.















Oh, and one more tip for you guys doing this. If you look at the 10th picture down there is a black bar. You are unbolting the top nut from that piece (then you can move it up, have someone hold it up or undo the hose attached to it). After that unbolt the BOLT that is bolted into the engine.
The bottom bolt is the easy one because there isn't the bar in the way and if I recall it's just a single BOLT. This kinda confused me so I just though I should clarify.


Good tip - I didn't do that because it's not really necessary to get the flange on/off, but thanks for adding that http://****************.com/smile/emthup.gif


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## Erotas (Aug 23, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (mross71)*

I've had the coolant flange fail on me twice.
Radiator fan control module was working intermittently. Didn't realise the first time.
Radiator fan control unit is not part of the ECU







, have to test it independently.
This seems to be the weakest point on the colling system and that's why it fails. 
Awesome DIY! http://****************.com/smile/emthup.gif 


_Modified by Erotas at 7:53 PM 11-17-2007_


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## Athfar (May 10, 2006)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (Erotas)*


_Quote, originally posted by *Erotas* »_I've had the coolant flange fail on me twice.
Radiator fan control module was working intermittently. Didn't realise the first time.
Radiator fan control unit is not part of the ECU







, have to test it independently.
This seems to be the weakest point on the colling system and that's why it fails. 
Awesome DIY! http://****************.com/smile/emthup.gif 

_Modified by Erotas at 7:53 PM 11-17-2007_

Hang on are you saying that it is building TOO much pressure causing the flange to fail? How did you go about testing your control unit?
Cause check this out http://forums.vwvortex.com/zerothread?id=3546893
Edit: Added URL


_Modified by Athfar at 8:20 PM 11-17-2007_


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## Erotas (Aug 23, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (Athfar)*

Yep.
Mine exploded twice like the pic below.








There is a test sequence in the Bentley.
You jumper two of the connectors and if the fans run, the control unit works.


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## Athfar (May 10, 2006)

How much did the control unit cost and was it hard to replace (I may just replace it instead of testing it because chances are it is intermittent)? Where about is the control unit? Seems like it would be part of the pump... 
I have gone soooo long without spending the 90 bucks for a bently manual telling myself that I will sell the car before I do it...


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## Erotas (Aug 23, 2003)

*Re: (Athfar)*

The Cooling Fan Control Unit is around $90 -100.
Just sits next to the fans, under the battery.
Part No: 1J0 919 506 K


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## Athfar (May 10, 2006)

*Re: (Erotas)*

Wait a second I read wrong. I was thinking it was like a coolant pump regulator... 
How does a fan controller cause too much pressure?








Do you mind posting the testing procedures?
Oh and thanks for the replies







.


_Modified by Athfar at 11:17 AM 11-19-2007_


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## Athfar (May 10, 2006)

*Re: (Athfar)*

Bump for testing procedures or more info please


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## crillforreal (Apr 13, 2007)

*Re: (Athfar)*

Great DIY-- i have had a coolant leak for about 3 weeks and couldnt find out where- after seeing this i decided to give it a try and sure enough my flange was shot. http://****************.com/smile/emthup.gif


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## pcfrias (Jan 13, 2008)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

I came across your DIY in search of same exact problem I am having now. THANKS and this is really great! http://****************.com/smile/emthup.gif Exactly what I'm fixing at this time.
I had problem removing top bolt with step stud on coolant flange. Hard to get the bar loosened up.
Also, any suggestions with loosening old hose connections with clamps? This is 1st time disconnecting these old hoses on my 2000 Jetta. Tried using vice grips to keep clamps open and used flat screwdriver to try to slide hoses off. I feel this 2 hr job has tripled due to tight hoses. Thanks,


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## GoonersRedWagon (Feb 10, 2005)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

Cracks me up seeing the quickcrete in the background 








Nice write up. It came in handy ! http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (pcfrias)*


_Quote, originally posted by *pcfrias* »_I came across your DIY in search of same exact problem I am having now. THANKS and this is really great! http://****************.com/smile/emthup.gif Exactly what I'm fixing at this time.
I had problem removing top bolt with step stud on coolant flange. Hard to get the bar loosened up.
Also, any suggestions with loosening old hose connections with clamps? This is 1st time disconnecting these old hoses on my 2000 Jetta. Tried using vice grips to keep clamps open and used flat screwdriver to try to slide hoses off. I feel this 2 hr job has tripled due to tight hoses. Thanks,

I usually use a #1 flat blade to break the seal, then twist and twist until it breaks free. Also, try using a little silicone spray under the edge of the hose...it will slowly penetrate the seal between the plastic and rubber and you can twist it off...then it also goes back on easier and conditions the rubber a bit as well.









_Quote, originally posted by *GoonersRedWagon* »_Cracks me up seeing the quickcrete in the background 








Nice write up. It came in handy ! http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif









Lol - the cement is leftover from when I built my fence and deck...it's now a solid chunk in a bag from absorbing humidity!


_Modified by MikeWire at 10:58 AM 1/31/2008_


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## wegrew (Aug 30, 2006)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (pcfrias)*

>> Oh, and one more tip for you guys doing this. If you look at the 10th picture down there is a black bar. You are unbolting the top nut from that piece (then you can move it up, have someone hold it up or undo the hose attached to it). After that unbolt the BOLT that is bolted into the engine.
Now I find that out. Took me about a half hour to figure out why the hell my flange wouldn't come off. Then I discovered what was going on.
Now if I can just get the dam retainer clip back onto the sensor. Can't get the sensor to seat far enough into the flange to get the clip in place. grrrr.
See my post here:
http://forums.vwvortex.com/zerothread?id=3689926



_Modified by wegrew at 2:46 PM 2-17-2008_


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (wegrew)*


_Quote, originally posted by *wegrew* »_>> Oh, and one more tip for you guys doing this. If you look at the 10th picture down there is a black bar. You are unbolting the top nut from that piece (then you can move it up, have someone hold it up or undo the hose attached to it). After that unbolt the BOLT that is bolted into the engine.
Now I find that out. Took me about a half hour to figure out why the hell my flange wouldn't come off. Then I discovered what was going on.
Now if I can just get the dam retainer clip back onto the sensor. Can't get the sensor to seat far enough into the flange to get the clip in place. grrrr.
See my post here:
http://forums.vwvortex.com/zerothread?id=3689926

_Modified by wegrew at 2:46 PM 2-17-2008_

I modified my instructions to include your tips - thank you!
Just a couple of other things to add: When replacing my clutch I noticed the underside of the flange was seeping coolant, and the bolts were torqued down correctly. So, I picked up another OEM flange from my parts and service shop in town - the newer OEM is much beefier and stronger and the seal seems to be a little better and bigger than the aftermarket. And after replacing it for the second time (Odometer is 125,100 miles) I hope I don't need to mess with it for a while.
Any more tips would be great - thanks!


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## leokempf (Nov 27, 2006)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

OK. This black "bar" is my nemesis. It will not move enough for me to get to the right nut. I even disconnected the hose at the rear of this "bar", but whatever this bar is connected to at the front of the car will absolutely not allow this piece to "pivot" or lift. Did I miss a step? Any ideas?
btw, this is an 01 golf.


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## MikeWire (Oct 20, 2003)

*FV-QR*

Hey Leo - I sent you an email. That black bar just rotates and pivots forward and up enough to get the new flange on. Hope it helps explain - maybe someone else can also chime in with their experience. 
FYI my engine could be a little different because I don't have SAI and mine is drive-by-cable.


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## leokempf (Nov 27, 2006)

*Re: FV-QR (MikeWire)*

Thanks for the reply. I got down to where I took both nuts from the flange, but can't get the bar up enough to get to the upper nut that actually bolts the flange to the head.
Is there a bolt holding this bar in place other than the one that is on the upper flange bolt?
mine's not pivoting at all...definitely not enough to get a socket on the nut that is behind that bar's bracket.


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## MikeWire (Oct 20, 2003)

*Re: FV-QR (leokempf)*


_Quote, originally posted by *leokempf* »_Thanks for the reply. I got down to where I took both nuts from the flange, but can't get the bar up enough to get to the upper nut that actually bolts the flange to the head.
Is there a bolt holding this bar in place other than the one that is on the upper flange bolt?
mine's not pivoting at all...definitely not enough to get a socket on the nut that is behind that bar's bracket.



IIRC there is one bolt - follow that bar down towards the front and you should run into it. Loosen it and the bar should then pivot up out of the way. That's the way mine was, but like I said earlier, your could be different.


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## leokempf (Nov 27, 2006)

*Re: FV-QR (MikeWire)*

OK. figured it out. I didn't realize it would pivot all the way over at the thermostat housing. Forward of the "bar" I loosened a nut pretty far down in there that holds a bracket for some wires. Then I gave the bar a tug and it pivoted. Thanks.
BTW...my "pink crusties" sort of wrap around where the head and the block meet...I'm guessing it did come from the flange though because the o-ring was in several pieces. Is this normal?


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## MikeWire (Oct 20, 2003)

*Re: FV-QR (leokempf)*


_Quote, originally posted by *leokempf* »_OK. figured it out. I didn't realize it would pivot all the way over at the thermostat housing. Forward of the "bar" I loosened a nut pretty far down in there that holds a bracket for some wires. Then I gave the bar a tug and it pivoted. Thanks.


Nice - I knew it was something simple. If you snap a picture I would post it up and add it to the DIY. 

_Quote, originally posted by *leokempf* »_
BTW...my "pink crusties" sort of wrap around where the head and the block meet...I'm guessing it did come from the flange though because the o-ring was in several pieces. Is this normal?

Sounds normal - mine had pink crust there too, and when I changed my clutch I found more that had leaked down into the trans housing...that's when I changed the flange for the 2nd time. That G12 is pretty tough stuff to scrape off when it dries lol.


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## leokempf (Nov 27, 2006)

*Re: FV-QR (MikeWire)*

trouble in paradise. I got the coolant back in, looks great. However, I noticed on my test drive that the speedo does nothing and the fuel gauge is intermittent. Can anyone tell me which of the plugs I took off deals with those? I think I may have gotten some water in one...though I dried it with compressed air...maybe I screwed it up.
on the bright side...now would be a great time to drive to alaska and back....since no miles are being logged.


_Modified by leokempf at 2:04 PM 7-29-2008_


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## MikeWire (Oct 20, 2003)

*FV-QR*

Assuming you have a 5-sp. manual...I don't know about the fuel gauge, but your speed sensor is not hooked up. It sits on the drivers side, on top of the transmission, near the back. You may notice that you can twist the connector left and right. It's a square black plug with about 3 or 4 pins. Make sure it's plugged in ALL the way (till it clicks) or else it won't register.


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## leokempf (Nov 27, 2006)

*Re: FV-QR (MikeWire)*

It's actually an automatic. The sensor I think you're talking about has a soft heat shield type cover you slide over it. See the picture. I have the digital version of the bentley manual, and I have a diagram of where it's supposedly located, but I can't locate anything else in the diagram.
Is that it? I guess I'll start a new topic for these problems if nobody here has any ideas.


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## raddo0125 (Feb 13, 2008)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (pcfrias)*

ahh yes that bastard... had it blow on me at a show... same thing happened with my rado at a diff show.. hmm i did it a little different..


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## bootymac (Apr 19, 2005)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*


_Quote, originally posted by *MikeWire* »_DIY: Replacing driver side coolant flange on a MKIV 
Coolant flange part # from ECSTuning:









Great write up! Only thing I would note is that the flange from ECS is not an OEM piece and... SUCKS! I replaced mine with ECS' flange and it was still leaking. As I removed it to investigate the problem, the flange broke in half in my hands. I ended up replacing it again with an OEM flange, which cost about $30.
When my original flange was leaking, I noticed dried coolant on top of the transmission. However, when the ECS flange was leaking, coolant migrated to the back of the engine, specifically where the head and the block met, and dripped all over the place.


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## MikeWire (Oct 20, 2003)

*FV-QR*

Thanks bootymac - I agree with you - (it's in my notes just below the second picture) I replaced mine for a second time (when replacing my clutch) because the non-OEM part failed and was leaking - more like seeping. It was easy to replace with the tranny out! I got mine for about $20 at our local VW service shop.


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## d1rty2.0 (Jun 16, 2008)

*Re: FV-QR (MikeWire)*

I heard there's an aftermarket metal flange for the MkIII could there be one for the MkIV? I haven't seen it yet, if so... this would solve all our problems up ahead on the road.


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## PedroV1 (Aug 9, 2007)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

Dude thank for this great DIY...I'm going to be doing this in addition to a timing belt and water pump on my MK4 this weekend...


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## grueger (Feb 28, 2005)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

what happened? after changing the flange im not getting heat from the heater and my temperature is getting hot than usual.


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## Ski-guru (Mar 16, 2008)

is there a bleed hose/valve on the mk3 obd2 engines?...i did a coolant flush in October and it was a b*tch bec i i disconnected the lower rad hose and coolant went everywhere...aslo will the drain hose/valve get rid of the air bubbles in the system? i got a buddy that needs to flush...
thx


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## vr6* (Jan 23, 2005)

$29.07 from VW in south florida today. i thought the gasket was shot, but once i removed it, that crappy plastic had cracked. not a hard job, 2nd time in a 2nd VW i've had to replace it. to use a plastic cooling contraption seem stupid to me, but an obvious money maker for VW for people that don't work on their cars, i guess. score 1 for corporate VW.


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## blanco1dbl2 (Jun 28, 2007)

*Re: (vr6*)*

Bump for a old thread....
Just did this today ....$23.00 for the part from VW stealership







and from the time I opened the garage door to the time I closed it took an hour and a half.
Excellent DYI thanks


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## cal2005 (May 3, 2009)

*Re: (blanco1dbl2)*

broke one of the two bolts securing the flange to the engine block... any tips on getting it out would be greatly appreciated. we tried vise grips, but they're just stripping the bolt. does anybody have any experience with PB Blaster?


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## cal2005 (May 3, 2009)

*Re: (cal2005)*

picture of the aftermath:


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## BlackSunshine (Mar 8, 2005)

*Re: (cal2005)*

PB may work, just let it soak in. Then tap it to break it loose. 
BTW, this DIY was awesome, just used it to change my flange, worked out great. http://****************.com/smile/emthup.gif


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## spitpilot (Feb 14, 2000)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (bootymac)*


_Quote, originally posted by *bootymac* »_
Great write up! Only thing I would note is that the flange from ECS is not an OEM piece and... SUCKS! I replaced mine with ECS' flange and it was still leaking. As I removed it to investigate the problem, the flange broke in half in my hands. I ended up replacing it again with an OEM flange, which cost about $30.
When my original flange was leaking, I noticed dried coolant on top of the transmission. However, when the ECS flange was leaking, coolant migrated to the back of the engine, specifically where the head and the block met, and dripped all over the place.

No Chinese knock off parts please! http://****************.com/smile/emthdown.gif http://****************.com/smile/emthdown.gif http://****************.com/smile/emthdown.gif Every one I've seen has been crude and of poor quality...only buy from OEM quality suppliers in the EU! After having to send back a couple of nasty Chinese parts (motor mounts and an EMPI axle for my Passat), I won't buy without supplier telling me country of origin! Great DIY write up..only comment I'd add is to "Tighten flange mounting bolt and nut a little at a time, one then the other..DO NOT just crank down on one fastener or you run the risk of cracking/warping your new flange and having to do this whole drill over again!"










_Modified by spitpilot at 10:09 PM 5-11-2009_


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## JackP311 (Feb 10, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

I did this on my 337. (AWP 1.8T)
The part for this is 06A 121 133J. You can tell the difference by looking at the rear of the flange and seeing the 90* bend.


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## volks25 (Dec 14, 2001)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (spitpilot)*


_Quote, originally posted by *spitpilot* »_
No Chinese knock off parts please! http://****************.com/smile/emthdown.gif http://****************.com/smile/emthdown.gif http://****************.com/smile/emthdown.gif Every one I've seen has been crude and of poor quality...only buy from OEM quality suppliers in the EU! After having to send back a couple of nasty Chinese parts (motor mounts and an EMPI axle for my Passat), I won't buy without supplier telling me country of origin! 

^^^ what he said. The second I saw made in China, I automatically guessed that the OP needed to redo this job with a OEM part. Sad that ECS is selling sub-par parts to make a few extra dimes.
This is a great DIY. I noticed that this flange, even OEM, will warp over time. It's the same type of problem found on mk2/mk3 water pump/thermostat housings, they eventually warp and fail. It's now a maintenance item on my list, good to change when coolant is due.


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## georanma (Nov 13, 2007)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

So, I just found out my water flange was crack by the base where it is bolted onto the engine on Wednesday. I managed to get the part Friday for a 12 dollars at the local european parts store. My friend, who has been working on my cars as long as Ive been driving, was kind enough to replace the part free of charge. Now, I had to be at my weekend job during the actual replacement process. Because of this situation, I was not there to see if he had saved or saw the seal between that sensor and the flange. My roommate delivered my care to me at work today, and I found that the seal couldn't be in place due to a leakage from around the sensor. I did not see the seal on the ground where my car had been parked, so it looks like I need to get another one. Does anyone know the size of the seal, if there is any thing special about it, and maybe suggestions of where I can get one. Im gonna call the parts store monday and see if they have it, otherwise I guess ill call the dealership and get raped over a rubber ring.


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## rbboyl (Aug 24, 2009)

*What is this hole?*

Great DIY! I'm in the process of doing this right now and I got the coolant flange removed. However, I noticed that on the side of the engine block, below and to the right of the hole where the flange goes, there is a small threaded hole. 
It looks like something is supposed to go there but I'm not sure.
I attached a couple pictures below with the hole circled in red. Can anyone provide any insight?


















_Modified by rbboyl at 6:44 PM 8-24-2009_


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## fissionreaction (Mar 18, 2008)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

thank you for the diy...the replacement was very easy to complete http://****************.com/smile/emthup.gif


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (volks25)*

Haven't checked posts in a while...
But yes you guys are correct about the OEM housing - get it, and don't get a replica or copy. It's not that expensive. I don't think ECS had the OEM part in stock and I had to do the repair ASAP because of the leak. It lasted until I replaced my clutch, and I noticed it was leaking again, so I made sure to get the OEM part that time. Replacing the housing was much easier with the tranny out of the car.








Thanks for all the + comments guys, hope the DIY helps some of you out!


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## nhjeffs (Feb 26, 2009)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

Great DIY. Thanks for all the information and photos. Other than breaking the retaining clip for the temp sensor, everything worked out great.


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## nmjetha (Apr 24, 2009)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

I take my flange is leaking??? Check my pics below, what do ya think??


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## FL 2.0L (Aug 1, 2002)

Good bet.


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## makeluvtomyvw (Jun 8, 2007)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o… (MikeWire)*

just did this this weekend, your instructions made it easy, thanks bro http://****************.com/smile/emthup.gif 
oh yeah and i think ive got everyone beat $32 from the stealership, but at least they didnt charge me for the oring


_Modified by makeluvtomyvw at 10:10 PM 3-28-2010_


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## eqlou (Dec 30, 2004)

being the great mechanic that I am, I overtightened and stripped the thread on the block. anyone have any suggestions?


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## benfica 8v (Nov 16, 2006)

i replaced 2 coolant flanges and i also got new o rings and used the high temp gasket sealer and i still have pink putty building around there....and now i have a serious leak but i have no idea where it is...no g12 on ground and im filling up 1L of g12 every 3 days


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## java959 (Aug 9, 2001)

*Re:*

DIY helped me much! No more leaking coolant!!!! http://****************.com/smile/emthup.gif 
Next up is replacing the front oxygen sensor @ the exhaust manifold! I know there's a DIY for this somewhere too!


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## iam4uf (Jun 5, 2008)

Just completed the job. I did not loosen the bolt on the bar. There was enough play in it to move up up a couple of inches to get it out. Thanks for the write up.


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## Southernbahn (Jul 26, 2010)

*Question about this job on a 1.8T*

Helping my son do this job on his 2004 GLI. The bottom stud mounting for the coolant flange is also holding a bundle of aluminum fuel lines. The bracket holding the fuel lines needs to come off that stud before the flange can come off. Is it safe to push the lines that far (about 3/4 inch) without causing trouble, or do I need to back the stud out, or am I missing some trick? Any suggestions, would be much appreciated.

BTW, this is an excellent DIY post. Thanks for doing it.


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## MikeWire (Oct 20, 2003)

Haven't checked the thread in a while - glad to see it's still useful! :beer::beer:


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## radink2 (Dec 11, 2006)

MikeWire said:


> Haven't checked the thread in a while - glad to see it's still useful! :beer::beer:


Thanks Mike. Im getting ready to do this now. What is the best way you found to clean the metal on the head? I was thinking fine grit paper or small wire brush.

Thanks
Mark


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## MikeWire (Oct 20, 2003)

I'm assuming you mean what you would clean the gasket area with? I would use some carb cleaner on a rag to remove any dirt etc. It should be pretty clean already, but you always want to make sure the mating surface is really clean.

To clean up the oozing and crusty G12, I use a 50/50 mix of simple green and water, after everything is repaired and leak free. I actually use this on my entire motor and engine bay.

Good luck!


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## radink2 (Dec 11, 2006)

MikeWire said:


> I'm assuming you mean what you would clean the gasket area with? I would use some carb cleaner on a rag to remove any dirt etc. It should be pretty clean already, but you always want to make sure the mating surface is really clean.
> 
> To clean up the oozing and crusty G12, I use a 50/50 mix of simple green and water, after everything is repaired and leak free. I actually use this on my entire motor and engine bay.
> 
> Good luck!


I pulled the flange off and there is crust around the hole in the block. The gasket and flange going back on is new, so I assume I don't need to clean that. I will try the ol' simple green. Thanks!

Mark


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## Albertkvw (Aug 19, 2010)

thanks a lot, took me about hour and half, make sure u get all hoses and air box out of the way makes it much easier.


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## ledgebutta (Jun 22, 2008)

*coolant flange*

i tryed autozone and they dont have it and dont even know what im talking about. is there some where i can order it? or is there a different name for it? alls i know is people at auto zone are ****ing retared and i dont know how they got jobs there


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## Kaie (Jun 15, 2005)

ledgebutta said:


> i tryed autozone and they dont have it and dont even know what im talking about. is there some where i can order it? or is there a different name for it? alls i know is people at auto zone are ****ing retared and i dont know how they got jobs there


The flange?

If you want to order online. GermanAutoParts.com , ECSTuning.com, Or my personal favorite due to the cheaper prices, brand of part disclosure and free shipping on orders over $50 .. AutoHausAZ.com.

If you want to pick it up locally, I would go to a local VAG shop that also sells parts. Or the VW dealer.

My local NAPA carries Pentosin G12. They could also most likely order G12+ or G12++ if you prefer those. I just recently did a complete coolant system overhaul this last week and went with G12++.


Also..

This may or may not have been mentioned, but i wouldnt put any type of gasket sealant in my coolant system.


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## MikeWire (Oct 20, 2003)

ledgebutta said:


> i tryed autozone and they dont have it and dont even know what im talking about. is there some where i can order it? or is there a different name for it? alls i know is people at auto zone are ****ing retared and i dont know how they got jobs there


It's all in the DIY...I even gave you the part #'s from ECS (unfortunately I just noticed they have updated their part #'s, so I will update appropriately). No local FLAPS will be able to help you with either the flange or G12, so Kaie is correct...order online, or visit your dealer. And, yes, please buy the OEM - the OEM part is much heavier duty than the aftermarket design. I ended up changing it a second time when I changed the clutch on this car.

ECS - Meyle coolant flange

ECS - 1 gallon of Pentosin G12




Kaie said:


> Also..
> 
> This may or may not have been mentioned, but i wouldnt put any type of gasket sealant in my coolant system.


It has been mentioned, and I stated it as optional in step #9. Do what you want, but I prefer to take out a little insurance - the aluminum head is very porous and the cast is rough, plus the aluminum and plastic flange will expand and contract at different rates and over time I feel that a small amount of high temp sealant on the rubber seal would not be out of line for this type of repair. 

To be exact and point out the flaw in your statement - no sealant is going IN the cooling system, just on the rubber seal that will contact the head material.

I have heard statements like this before, and I would like to hear some concrete facts as to why any type of sealant would be "bad". If you make a contradictory statement, be prepared to back it up. I'm not talking opinion, but FACT. 

I also would like to state that this car is still running, coolant flange leak free.


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## hmsmart (Feb 17, 2011)

*haha*

I am fixing to fill mine up with quickcrete and sink it.


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## pretrender (Jun 12, 2011)

*coolet flange 2001 jetta*

Hi hope someone can help with mine 2001 jetta 1.8 turbo i change the coolant flange but when i took out the screws for it they were like a four point head not a flange head bolt how do you get them tight so it does not leak . I try the way i took them out use a four point screw driver but leak bad. i did go get 10 mm flange head bolts so i can use a torque i think 5 to 7 lbs. thanks if someone can help


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## Vmjacinto-sanchez (Aug 23, 2011)

*Confused? What is the difference between part num 1j0 919 506 k and 1j0 919 506 E ?*

So do any of you know the difference between these two parts? The part that I took off of my car (Audi TT quattro 2000) is 1j0 919 506 E, which was under the battery, but I can't find anywhere online that has that item number...the only one I keep on running into is the one ending in K. Are they the same thing? Please help...I am knew at diy on my car, but determined, since I don't want to get robbed my the dealer.
-vic


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## MikeWire (Oct 20, 2003)

Vmjacinto-sanchez said:


> So do any of you know the difference between these two parts? The part that I took off of my car (Audi TT quattro 2000) is 1j0 919 506 E, which was under the battery, but I can't find anywhere online that has that item number...the only one I keep on running into is the one ending in K. Are they the same thing? Please help...I am knew at diy on my car, but determined, since I don't want to get robbed my the dealer.
> -vic


Not related in the slightest to the thread content or DIY, but I'll bite 

Looks like a model year split - E is a 10 pin module and K is a 14 pin module, so they are different. Get the E version, ECS sells it:

http://www.ecstuning.com/Search/1j0_919_506_E/


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## my11g (Jun 23, 2003)

i bought my flange from german auto parts, is this an OEM part? I did not see any manufactures stamp of any kind on it.

Should I send it back and buy from the VW dealer?


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## MikeWire (Oct 20, 2003)

my11g said:


> i bought my flange from german auto parts, is this an OEM part? I did not see any manufactures stamp of any kind on it.
> 
> Should I send it back and buy from the VW dealer?


GAP usually sells OEM parts, but if you can't verify that it's and OEM replacement, then send it back and get the OEM.


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## my11g (Jun 23, 2003)

MikeWire said:


> GAP usually sells OEM parts, but if you can't verify that it's and OEM replacement, then send it back and get the OEM.


So how do I verify that? Is it just by VW logo stamped on the part or is there some other difference as well.


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## ianeLay (Oct 18, 2011)

Hey,

My first time changing this infamous flange. The directions seem helpful but I can't see the pictures anymore and I think they would really make this job easier. I'm a newbe at this mechanic stuff


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## MikeWire (Oct 20, 2003)

my11g said:


> So how do I verify that? Is it just by VW logo stamped on the part or is there some other difference as well.


If you can't verify the part, then it's more than likely not OEM. It should have some stamping and/or come in the OEM box.



ianeLay said:


> Hey,
> 
> My first time changing this infamous flange. The directions seem helpful but I can't see the pictures anymore and I think they would really make this job easier. I'm a newbe at this mechanic stuff


My primary DNS host is refreshing, so give it a bit and try again in about an hour.


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## MikeWire (Oct 20, 2003)

Pictures back up :thumbup:


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## endersm (Oct 18, 2008)

thanks for posting this diy.

my 2.slow sprung a leak this morning.

What is the part number (or link to ECS,) for the "small" o-ring and clip on the temp sensor?

thanks again.
andrew


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## MikeWire (Oct 20, 2003)

endersm said:


> thanks for posting this diy.
> 
> my 2.slow sprung a leak this morning.
> 
> ...


Ok guys, I made the DIY but I can't hold your hand. Go to ECS and look it up. FYI, the o-ring usually comes with the sensor.

What I found:

Clip - http://www.ecstuning.com/Volkswagen-Jetta_IV--2.0/Engine/Cooling/Temperature_Sensor/ES3055/

Sensor O-ring - http://www.ecstuning.com/Volkswagen-Jetta_IV--2.0/Engine/Cooling/Housing_-_Flanges/ES264172/


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## endersm (Oct 18, 2008)

Thanks for the reply - didn't mean to come off like a q q whiny baby, was just thrown off by ECS saying "...O-Ring that is on most clip-in cooling sensors/senders..." rather than "this totally fits the temp sender in your Mk4".

at any rate, the part is on the way and I appreciate your confirmation of the correct part number!

:beer:



MikeWire said:


> Ok guys, I made the DIY but I can't hold your hand. Go to ECS and look it up. FYI, the o-ring usually comes with the sensor.
> 
> What I found:
> 
> ...


----------



## MikeWire (Oct 20, 2003)

No problem, I wasn't trying to be a dick, although I think I did a pretty good job at it  

That sensor clip and o-ring fits a lot of different models and gens of VW and Audi and you should be good with it. ECS could be a little more specific on what part fits, for sure. 

Glad the DIY helped, and good luck with your work :thumbup:


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## DizzleCo (Oct 10, 2001)

*Thank you!*

Did this repair yesterday after a month plus of leaking and topping off with water. Since the temp dropped to 8* tonight glad I got all that water out the radiator and everything locked back up.

My only suggestion and maybe it was just my bad luck, but I would say spend the extra $.69 and pick up a new coolant sensor clip. Mine snapped as I put it back on.


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## Sovietaced (Feb 5, 2010)

Ordering the part now, very excited to get rid of this leak that has caused me so much grief!


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## 2ndGenVW (Jan 15, 2006)

Thanks for the great DIY!

I just did it and taking my time it took me about an hour.


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## djgromit (Mar 5, 2012)

Thanks so much for this DIY! I've been systematically replacing hoses since one burst, and I think I might have inadvertently cracked the seal on the flange when I was replacing the top heater hose while trying to wrestle it off the flange.

Your instructions were really clear and easy to follow. I don't do a ton of my own work, but was able to knock this one out no problem.

I wasn't able to walk away after 2 hours...I spent the bulk of the day doing it, but I was also doing a lot of clean up along the way, and I swapped out a few more hoses while I was there (bottom heater, and the pair of oil cooler hoses).

Thanks again for the great DIY!


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## corporate.joe (Dec 6, 2008)

Did this myself a little over a week ago. It's the most involved DIY I have done so far. I typically stick with brake and oil changes with no problem. I made sure to put twist ties on hoses that I disconnected as a visual reminder. I have pictures of the crack that was causing the leak and where I finished off the smaller hose inlet on the bottom of the flange. Whole thing was looking fragile.

No more adding distilled water every 3 or so days!

Thanks for the informative thread!

Joe-



















Sent from my Galaxy Nexus using Tapatalk 2


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## spelunkerd (Jul 14, 2010)

*I just posted a video of this repair*

Special thanks to MikeWire and all of the contributors for helping me do this repair yesterday. It's obviously an infamous problem, and many more will need help to the future. I did a Youtube video of this repair, for the benefit of those to come. In the video description I included a link back to this thread as well. 

http://youtu.be/3ShCTe8YzMI


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## jetta.911 (Jul 20, 2011)

just wrapped this up.. only issue is I CANNOT get the plastic clip back in on the flange to hold the sensor in? everything is back on the car and set to go but this is a no go... Ideas?


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## jetta.911 (Jul 20, 2011)

OK, don't kill me, I was putting the clip in the wrong way, instead of putting it in with the slots on both sides, I was trying to put it in through one side. 

Ok, I know stupid, but just an FYI to everyone else!


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## marticaapicella (Oct 6, 2010)

awesome write up! helped a bunch. thanks so much. :thumbup:


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## rxmarccall (Jun 5, 2012)

*What do you guys think?*

Hey guys so i just wanted to post a few images and see if you guys would agree that my problem is the same with the coolant flange. Unlike the original poster, I do not see coolant on the ground but I am losing coolant at a decent rate. Please look at the images here and let me know if you think my coolant problem is indeed the coolant flange, if so i plan to change it this weekend. Hopefully it is this and not a blown head gasket. Thanks so much


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## germancarnut51 (Mar 23, 2008)

Yeah, that looks like a coolant flange leak, but you also have long term oil leaks from the looks of it.

You need to replace the valve cover gasket, oil filler cap gasket, PCV valve grommet, oil pressure sensor, and UIM gasket to take care of the oil leaks.

And you better order the coolant flange soon, or you'll be paying $30+ for one at the VW Dealer (if they still stock them, the local VW Dealer to me does not stock anymore). AutoZone, Oreilleys, and NAPA can special order one for you for around $30, but they don't stock them, and the quality is spotty.

AutohausAZ has MTC brand coolant flanges for $6, but they're are junk. I gave away the ones I got from there.

Europartsdirect has Meyle, but the price of Meyle parts has been climbing with their reputation for quality. They cost $12 now.


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## spelunkerd (Jul 14, 2010)

*agreed*

Yes, I agree. The reason you don't find a pool of coolant under the engine is that small volumes drop onto hot parts and evaporate off before they hit the ground. Underlying structures allow a bit of pooling as well. In addition, leaking only happens when the system is under pressure, so if you don't idle for long in one location you will not see fluid dripping underneath. With a compromise of the system there, air can reflux back into the system, which allows fluid level at the flange to drop, reducing fluid spillage when the engine is at rest. Pressures quickly fall with engine off and a leak. The net effect is chronic 'mystery' leakage, and ineffective cooling because of air pockets in the engine cooling passages. 

It's concerning but not surprising to learn that there may be rising cost for parts as these engines age. My OEM flange here in Canada cost $48 at the dealer.


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## cleland (Aug 9, 1999)

I'll be doing this replacement on Saturday, wish me luck! I recently developed a coolant leak after I had mistakenly removed & replaced the factory coolant flange :banghead: on my 2002 Jetta -- it's a long story but in any case I'm getting a slow drip directly under the engine when it's parked after driving. I got under the car with a flashlight and it appears that the drip is coming from the backside of the engine, but my bet is on the flange (since I had removed it) and that the coolant is running along a hose or other and finally dripping out onto the ground. 

With that in mind, are there any coolant fittings or other leak-prone places on the backside of the engine block? It's very hard to see down there and just wondered if there was something else that could possibly be leaking that I can't readily see.


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## intro (Oct 3, 2005)

Sorry to bring this back but if my leak was coming from the green plug/sensor, is it ok to just change the o-ring or is it possibly the switch? Is it standard practice just to replace all 3 because I will while I'm in there?

Thanks.


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…*



intro said:


> Sorry to bring this back but if my leak was coming from the green plug/sensor, is it ok to just change the o-ring or is it possibly the switch? Is it standard practice just to replace all 3 because I will while I'm in there?
> 
> Thanks.


Should be easy to swap the sensor out, it's a good place to start. If your flange seal is leaking you'd of course want to change the flange.


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## intro (Oct 3, 2005)

No coolant leak where the flange mounts to the head, just around the hole where the plug goes in. So it is possible for the sensor itself to cause the leak and not the o-ring?


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## MikeWire (Oct 20, 2003)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…*



intro said:


> No coolant leak where the flange mounts to the head, just around the hole where the plug goes in. So it is possible for the sensor itself to cause the leak and not the o-ring?


Doubtful it's the sensor - the rubber o-ring has probably shrunk and hardened. I'd replace both the sensor and o-ring and I bet your leak stops.


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## intro (Oct 3, 2005)

Athfar said:


> I wouldn't recommend putting that gasket sealant on there for three reasons.
> 1) It isn't really the seal that fails it is the composite / plastic underneath in my case. It ends up melting and deforming the plastic which just happens to take the seal along with it.
> 2) The type of gasket sealant you are using isn't designed for these types of press on rubber seals and in some cases can make the seal work less efficiently by gumming it up.
> 3) You are just making it harder to take off the next go around.
> ...



So I think this is what is confusing me and I'm hoping someone can chime in as it has caused me a great deal of frustration today (that ended with me dropping a bolt in the tranny, fortunately sorted that out) since I forgot to take pictures of the set-up last weekend.

First of all, are the bolts for the flange regular 10mm hex bolts? I had my thermostat cover housing bolts out at the same time so I'm getting confused. One pair is hex and the other is allen style, then I have that black bracket with 3 holes and a stud with a nut and a plastic cover that screws on. It seemed the two allen bolts were better suited to the therm cover so I went that way and they tightened down fine. When I put on the Coolant flange with the 10mm hex bolts it didn't seem to torque down right, at the top especially. If I'm understanding correctly (and I'm not supposed to use the allen bolts I used on the therm cover) then the upper part of the flange is attached with the stud, does that mean the other 10mm is for the bracket? Wish I had a picture of the proper orientation of the bracket as I am completely lost here and don't see the bracket in any photos in this thread.


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## intro (Oct 3, 2005)

I'm actually beginning to wonder if that metal bracket even goes here...I know that as I was doing my timing belt I set aside pieces with their respective bolts aside, the stud with the nut on it was sitting in one of the holes of this bracket that I can't seem to figure out.

It's possible the bracket goes somewhere else and I just messed up while organizing.


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## rommeldawg (May 25, 2009)

intro is this on the 02 jetta wagon? if so you should have two 6mm stud/bolts (10mm would be socket or wrench size to fit the head) that attach the flange to the head and hold the water pipe in place. the two that hold the thermostat housing are like the ones in photo and are 6mm with 5mm allen centers but also allow for 10mm socket. as far as that bracket dont sweat it just make sure nothing is dangling where it could become a problem.


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## intro (Oct 3, 2005)

Thanks for the response man, I'm still a little perplexed.

I used 2 Allen head bolts to replace the thermostat cover. These in the picture seemed too small for the therm cover and they are not allen head. What about the longer stud with the bit on it?

Edit: The bracket and stud have been identified: power steering reservoir.


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## MikeWire (Oct 20, 2003)

I see your edit there, and I'm glad you found the spot for the bracket and the bolt.

The small plastic cable holder sits on the stud at your PS reservoir and it holds the cable to a sensor in that area.

:thumbup::thumbup:


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## intro (Oct 3, 2005)

Hey guys, back for more advice on this. So a month after replacing the flange driving without issue, I noticed the coolant level was dipping in the reservoir, I added some coolant thinking maybe I hadn't tightened down the reservoir cap enough but the leak was going faster now and I was seeing coolant collecting on the top of the transmission below where the flange is. None of the hoses in the area felt wet or looked crusty and on inspection no visible leaks on the head/flange itself, however I noticed some play in it and when I moved it coolant came spilling out. I re-torqued the bottom bolt tight (it had loosened) and attempted the top bolt again but it still won't tighten up well. This was an issue when I had installed a month ago so is it possible that vibration loosened the bottom bolt up?
What can I do about the top bolt? Was it stripped by the a previous repair when the P.O. had it? There are indications of some other Mickey Mouse repairs like the SAI pump being held on with zip ties etc.


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## Marc1987 (Jan 24, 2010)

*Re: DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…*

Be veru careful.i snapped my top bolt into the block lol. Also make sure its seated, the black bar thing thay connects is a pita.you need to push it back then tighten

Sent from my Note 2 using Tapatalk 4


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## Mouses (Aug 24, 2013)

*What do you guys think, coolant flange problem?*

Hi guys.
I have a 2003 2.0 Jetta and I think that I have the same problem with the coolant flange but I’m not sure if I only have this problem, because I see a lot of coolant leak. I would like you guys to take a look at my images, and hopefully you can give an opinion about it.
I used the “liquid Aluminum Radiator Stop Leak” but I don’t think this will solve my problem.
Thanks guys, greetings from Mexico.:thumbup:


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## Sovietaced (Feb 5, 2010)

Mouses said:


> Hi guys.
> I have a 2003 2.0 Jetta and I think that I have the same problem with the coolant flange but I’m not sure if I only have this problem, because I see a lot of coolant leak. I would like you guys to take a look at my images, and hopefully you can give an opinion about it.
> I used the “liquid Aluminum Radiator Stop Leak” but I don’t think this will solve my problem.
> Thanks guys, greetings from Mexico.:thumbup:


That's it.


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## jacobroufa (Jun 18, 2012)

This is a lot less difficult than I thought it would be. The toughest part is moving that stupid metal tube up high enough to get at the bolt behind it -- you barely have clearance for it but hold it tight as high as you can and you should be good. Thanks for the writeup! :thumbup:


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## clamskittles (Jan 14, 2007)

Just to clarify. If i'm looking at this diagram 










I need item 12 and 13, and then the "y-connector" you speak of would be 20?

Thanks again for the help!


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## papitou5 (Apr 29, 2014)

Thanks for the DIY! 👍
I was able to take care of my slow coolant flange leak.
I also replaced thermostat + housing at the same time. 
It's quite a messy job though!


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## DeepBlue01 (Jan 16, 2016)

Great DIY and lots of good info in the posts. I was searching for why my Manual tranny was leaking red/pink fluid and came across this. I swapped the flange out this weekend and the old one literally crumbled in my hand. Thanks to all who contributed.


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## lairdwd (May 20, 2014)

*Just changed my crack pipe*

Not too bad. Thanks for the write uip!


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## lairdwd (May 20, 2014)

lairdwd said:


> Not too bad. Thanks for the write uip!


So as part of replacing the crack pipe, I turned the heat on/off a couple times and the bushing door blend pin went kaput. I also learned that my crack pipe had a leak! 

Both are fixed now. The crack pipe was leaking from the cooler line. I had not put the hose clamp exactly where it was prior to the repair, and the slight re-orientation introduced a leak. I put it back where the dig marks were in, and now it fits like a glove. No more leak.


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## MartyK1 (2 mo ago)

Hi Mike
Did you see why it was leaking?
Why did you change the flange; was it cracked?
I'm planning to just change the O-ring.
Tks


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