# how do i bleed air out of cooling system?



## 04silverjetta (Jul 19, 2008)

*Please help me! quick coolant flush question*

I have a 04 jetta and doing a coolant flush. I cannot find the bleeder valve! How do i bleed the air in the system? I seem to have a lot of air and causing me to overheat.


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## 04silverjetta (Jul 19, 2008)

i have a 2004 jetta. just did a coolant flush and can't get the air out. the upper and lower radiator gets hot,and i have heat coming out. AC works fine. idles at 190 deg. as soon as i start driving, the car overheats. is there a bleeder valve on this car?


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## Boostin20v (Mar 22, 2000)

*Re: how do i bleed air out of cooling system? (04silverjetta)*

have you tried taking the top off the coolant res while its running?


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (Boostin20v)*

yes, i left it running with the top off, engine running blasting the heat. Then i closed it, drove around the block and started overheating. Then I parked it, opened the tank again slowly, and the coolant starts rising and ready to explode so i have to vent it slowly. I could hear bubbles in the lines when I shut the engine off.


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## wolfinsheep (Sep 2, 2007)

*Re: how do i bleed air out of cooling system? (04silverjetta)*

do you have a 50/50 mix of coolant and water? It sounds like the boiling point is too low.


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (wolfinsheep)*

can you tell me out to properly bleed it? is there a bleeder screw or something?


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## igotaprestent4u (Nov 2, 2002)

*Re: how do i bleed air out of cooling system? (04silverjetta)*


_Quote, originally posted by *04silverjetta* »_can you tell me out to properly bleed it? is there a bleeder screw or something?

run the car with the coolant top off so air can blead out of it. Add coolant as needed. May take 10 minutes or so.


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (igotaprestent4u)*

update: I went back to it the day after. The coolant in the tank was gone. I'm thinking it filled up throughout the system. I poured some more in to the MIN for now. I left the cap off, started the car and warmed it up to 190. The car stayed at 190, but the coolant level started going up and down and overflowed at times. Then it started smoking so i shut it off. I had heat coming out, the temp was stable at 190 and the lower radiator hose was cold, unlike last time.
Will this be a thermostat issue or could it be as bad as a waterpump? Can anyone tell me where the thermostat is located?


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (04silverjetta)*

last time when the lower radiator hose was hot, i had driven it for about a mile and started overheating.


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## Andaloons (Apr 16, 2004)

*Re: how do i bleed air out of cooling system? (04silverjetta)*

If it is holding the temp at 190 sometimes and not at others, then it is your thermostat.


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## thejordan (Feb 7, 2008)

*Re: how do i bleed air out of cooling system? (Andaloons)*

thermostat and/or waterpump.
whats your mileage?
my friend has an 04 jetta, he's had the waterpump replaced twice already.
the correct method for bleading air out:
since there is no bleeder valve, leave the cap off until car gets to temp. if your thermostat works you'll see the coolant level drop, then rise again after a few minutes, that means your thermostat is working. you should notice some coolant flowing from the return line, that means your waterpump is working. masage coolant hoses by hand. the process should take about 15 min. fill it to level, cap it then drive around, check levels again.
it's your waterpump if, the temp lowers at idles or stops, raises while driving/cruising.


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (thejordan)*

it sounds like it's the waterpupmp. mileage is at 55k. i'm gonna change the thermostat and see what happens. What else should I do if I have to end up replacing the water pump?


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## thejordan (Feb 7, 2008)

*Re: how do i bleed air out of cooling system? (04silverjetta)*

timing belt and everything related to that. expect to pay around $800 to get it done.


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## theswoleguy (Jan 25, 2006)

*Re: how do i bleed air out of cooling system? (thejordan)*


_Quote, originally posted by *thejordan* »_timing belt and everything related to that. expect to pay around $800 to get it done.

unless of course, you can do it yourself and save 500


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (theswoleguy)*

can someone please tell me where the thermostat is? how much should i expect to pay?


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## veedubwolfsburg (Jun 4, 2007)

*Re: how do i bleed air out of cooling system? (04silverjetta)*


_Quote, originally posted by *04silverjetta* »_can someone please tell me where the thermostat is? how much should i expect to pay?

Thermostat is on the front of the block right behind the alternator. It is inside the plastic coolant neck attached to the block there. It's honestly not that difficult of a job to replace the thermostat as long as you have figured out the right combo of u-joints and extensions to get to the two bolts.


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## GLiMKIV (Nov 12, 2006)

*Re: how do i bleed air out of cooling system? (veedubwolfsburg)*

That plastic impeller on your pump is probably broken. T/Stat is obviously the cheapest to do, so start with that. If you get the same results, you know its your pump. If you are going to do a pump, go the ECS Tuning to get the entire kit which includes the upgraded metal impeller. Worth every penny!


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## thejordan (Feb 7, 2008)

*Re: how do i bleed air out of cooling system? (theswoleguy)*


_Quote, originally posted by *theswoleguy* »_
unless of course, you can do it yourself and save 500









obviously, thats what i did, but i doubt that's a solution for him.


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## TooLFan46n2 (Oct 18, 1999)

*Re: how do i bleed air out of cooling system? (thejordan)*

I didn't see anyone mention it but when you replace the thermostat stick your hand into the hole and you can feel the waterpump to see if its broken.


_Modified by TooLFan46n2 at 10:14 PM 7-24-2008_


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## 04silverjetta (Jul 19, 2008)

well, i just did the timing belt for my a4 and had to take the front end off, but the jetta is retarded. the belts are all on the side. how do i get the most work room to access the pump? is there a writeup for this model?


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## 04silverjetta (Jul 19, 2008)

*Re: (04silverjetta)*

what kind of feeling should you get from a broken waterpump?


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## thejordan (Feb 7, 2008)

*Re: (04silverjetta)*

here's the timing belt/ water pump DIY
http://forums.vwvortex.com/zerothread?id=2840728
I recommend reading the ones for the other engines as well so that you better your understanding.
To get to everything you actually have to unmount the engine on one side and jack it up. Its about 3-5 hours depending on your competency (more for noobs). This isn't the easiest job and if you screw up your engine may be toast.
Remember, if you try to feel down for the waterpump (which i'm not sure is possible or easy to feel) your waterpump can still be broken. The waterpump breaks in 2 different ways: Either the plastic fins fall off or the shaft breaks so it doesn't spin.
****Do your preventative maintenance****


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## 04silverjetta (Jul 19, 2008)

*Re: how do i bleed air out of cooling system? (veedubwolfsburg)*


_Quote, originally posted by *veedubwolfsburg* »_
It's honestly not that difficult of a job to replace the thermostat as long as you have figured out the right combo of u-joints and extensions to get to the two bolts.

That pretty much is the whole job! How the hell do i get to the bottom one? How many u joints did u use and what angle did yall attack it from?
Also, should i even bother to take the hose off the plastic tube? prob not necessary, huh?


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## aeligos (Jul 24, 2011)

hi all i'm new here.

99.5 jetta 2.0L GLS

i have this same issue but somewhat different.

i replaced wp, thermostat. then i wanted to flush system with distilled water - with tank cap off.

on day 1 after replacements, i wanted to flush system with distilled water. reservoir tank took it down and temp gauge went to middle and high temp light went on...but fans didn't turn on. i ran it for 5 min but fans didn't turn on. top hose was hot/pressurized, bottom hose to t-stat was also hot. no leaks in system.

on day 2, i noticed liquid level in reservoir went down a bit more so i started engine and added more distilled water. fluid returned to tank as pink (old coolant) and fans would not turn on yet, only this time the temp gauge needle did not go up at all (stayed at 0) and high temp indicator light was flashing. also, top hose very hot and pressurized but bottom hose towards t-stat remained cool this time.

on day 3, liquid level of tank was at max level, i turned on car and ran it for a bit but again needle would not move from 0; fans would not turn on. fluid returned to tank again raising the level, and after a couple minutes; high temp light activated. again top hose very hot/pressurized but lower hose towards t-stat remained cool.

can the difference between day 1 vs day 2 & 3 be simply due to of trapped air? there is definitely a circulation problem but why won't temp gauge needle climb after day 1?

any suggestions would be great.

-.-


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## screwball (Dec 11, 2001)

Are you guys driving these things during the burping process and not just idling them? I've never gotten air leaks out of the system w/out actually getting onto a highway and romping a little before going back over everything to squeek more air out. Seems to be the only way my car will work that crap out.


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## aeligos (Jul 24, 2011)

my jetta is not driveable at the moment (expired license plate and sticker) and also i need to adjust timing belt tensioner (it's too tight).

regarding burping:

on day 4, i drained distilled water and added mixed g12+distilled water (50/50).

turned on engine for 7-10 min.

new observations:

1. no heat from HVAC system (air is cool).

2. high temp indicator light now does NOT come on (due to proper coolant mixture).

3. check engine light does not come on (should have mentioned this earlier, it never came on).

4. temp gauge needle remains at zero (won't climb at all)

some observations from previous days continue: top hose from engine to radiator is pressurized and hot; bottom hose from radiator to t-stat is cool and not pressurized...oh and fans still won't turn on.

any suggestions would be appreciated.

-.-


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## kwalla73 (Aug 26, 2011)

screwball said:


> Are you guys driving these things during the burping process and not just idling them? I've never gotten air leaks out of the system w/out actually getting onto a highway and romping a little before going back over everything to squeek more air out. Seems to be the only way my car will work that crap out.


 How do you drive around if your car's overheating? That's the problem I have with my 99 vw beetle. I flushed the coolant system and refilled it, however now I can't get the fans to come on because I think the air in the system is preventing the hot coolant from reaching the temperature sensors, thus preventing the fans from kicking in.


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## screwball (Dec 11, 2001)

that makes almost no sense.


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## kwalla73 (Aug 26, 2011)

screwball said:


> that makes almost no sense.


 What I'm trying to say simply is that I flushed the cooling system and refilled the expansion tank with coolant. I then started the car and let it run. I even took it for a spin down the block. The car overheated and the fans never came on.


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## groggory (Apr 21, 2003)

I found that if you park uphill like on a driveway, get the car warm, then while the engine is running unplug the upper radiator hose (while wearing thick gloves..cause steam will come out) wait for radiator fluid to come out, then push it back on the radiator. 

If a nice steam bubble gets trapped in the heater core its kinda tricky to get out. 

While you're doing that make sure that your coolant res has plenty of fluid in it the whole time. Never let it go empty during this process or you may introduce new air bubbles. 

Also, my personal theory... 

If I ever overheat I replace the radiator fluid. It seems that once you go over boiling your mixture of g12 : water is all screwed up and your boiling points and whatnot are never right again. Flush the whole system and replace with 50/50 water/g12.


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## jeeprnovru (Jun 24, 2011)

Ive been through all this with my 04 and I promise your WP is toast. They have em in stock at Advance Auto Parts for like 68 dollars and I did the job myself. But you must order some G12 coolant from VW or somewhere. the blue BMW cooland or any other kind will solidify and ruin your car. I did it my self with a pizza and a few hours and If you PM me ill let you use my Bentley Manual. eace:


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## shepa401 (Nov 30, 2009)

I just recently did my water pump and timing belt on my a4. To bleed the air out of the system i was told to pull one of the heater hoses slightly back from the heater core and there was a small pen sized hole for bleeding out air.


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## manyDUBs (Dec 26, 2002)

Try properly bleeding the air in the system: 

http://forums.audiworld.com/showthread.php?p=1635231 

Bleed hole picture: 

http://www.taligentx.com/passat/images/large/coolant_04_bleed.jpg 

DIY on coolant flush: http://www.taligentx.com/passat/maintenance/coolantflush/


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## manyDUBs (Dec 26, 2002)

Dude, 1st properly bleed the air out of the system, since you were only trying to coolant flush the system. 

No where in this thread have you indicated why, however many people have lead you to think that you have a bad waterpump and or thermostat. 

Was the reason for the coolant flush because your car was overheating or just maintenance?


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## benjbong (Sep 12, 2003)

*I'm having the same problem*

I have an 04 jetta 1.8t, I was driving for about 5 minutes when the temp guage pinned and the CEL came on. I popped the hood and the engine was barely even warm. Coolant seemed low, so i went to the closest gas station and bought some coolant and added some to the expansion tank. 

Later read you can't mix coolants, crap - need to flush out the green stuff. 

I got a new engine temp sensor from the dealer. 

To drain i took the top off the expansion tank, pulled out the rad drain plug and turned the car on. While idling i ran about 1 gallon of distilled water through until the water coming from the drain was clear. 

After coolant stopped running out of the drain i replaced the ECT sensor. 

With car running I poured my 50/50 mix of g12 into the expansion tank with the drain plug open until only the light pink mix was coming out then shut the plug, filled tank up and let car run for a few minutes, topped off as needed then closed the lid. 

Took car around the block - still overheating. 

Got the thermostat from the dealer, replaced the thermostat - lost about a pint of coolant in the process, refilled the tank and let the engine warm up - temp was at 190 but as soon as i started driving the temp gauge started climbing again. 

After reading it seems i didn't do the coolant flush properly - i didn't bleed air anytime and i didn't disconnect any hoses just pulled the plug on the bottom of the rad. 

Do i need to flush the coolant and start over with disconnecting hoses and bleeding the air or can i just pull the hose to bleed the air from where i am now? 

Also - with heat on full blast i never get heat - does that mean air pocket?


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## TooLFan46n2 (Oct 18, 1999)

benjbong said:


> With car running I poured my 50/50 mix of g12 into the expansion tank with the drain plug open until only the light pink mix was coming out then shut the plug, filled tank up and let car run for a few minutes, topped off as needed then closed the lid.
> 
> Took car around the block - still overheating.
> 
> ...


 Air pocket or bad waterpump. You need to "burp" the coolant at the lower hose so it gets to the thermostat. Jacking up the driverside will help a little but isn't required.


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## benjbong (Sep 12, 2003)

TooLFan46n2 said:


> Air pocket or bad waterpump. You need to "burp" the coolant at the lower hose so it gets to the thermostat. Jacking up the driverside will help a little but isn't required.


 I'm unsure of what the "burping" process is. Do i just run the car with the cap off the tank and shake the hose a little? Would i do that before or after bleeding?


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## TooLFan46n2 (Oct 18, 1999)

benjbong said:


> I'm unsure of what the "burping" process is. Do i just run the car with the cap off the tank and shake the hose a little? Would i do that before or after bleeding?


 Squeeze the lower rad hose and try to push the coolant towards the thermostat. I usually do this while filling up but you should be able to do it filled up. Remove the cap or use the coolant drain to help coax the air up and out of the system.


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## manyDUBs (Dec 26, 2002)

benjbong said:


> I'm unsure of what the "burping" process is. Do i just run the car with the cap off the tank and shake the hose a little? Would i do that before or after bleeding?


 
Read my posts for answers: Try properly bleeding the air in the system: 

http://forums.audiworld.com/showthread.php?p=1635231 

Bleed hole picture: 

http://www.taligentx.com/passat/imag...t_04_bleed.jpg 

DIY on coolant flush: http://www.taligentx.com/passat/main.../coolantflush/


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## benjbong (Sep 12, 2003)

manyDUBs said:


> Read my posts for answers: Try properly bleeding the air in the system:
> 
> http://forums.audiworld.com/showthread.php?p=1635231
> 
> ...


 Will i need to reflush the coolant or is it ok to just do the bleed process? Any old coolant in the block would have come out when i changed the thermostat.


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## benjbong (Sep 12, 2003)

*is this the heater core inlet and outlet?*

I've only seen pictures of the inlet and outlet hoses for the heater core on audis. Is this what i'm looking for in my mkiv jetta? This is on the airbox side not under the expansion tank.

Also, I noticed a ridiculous amount of corrosion at the bottom of the battery box - i understand the radiator thermo switch and fan control module are in that area, i'll check that out as well. Where exactly is the FCM? a pic would be great if possible


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## MK4BETOVW (May 12, 2012)

bump for answer^^


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## Madunix (Jul 23, 2013)

i don't understand how this thread just died out of nowhere at the most crucial part. can someone answer the last question please? i'm in the exact position as this guy.


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## Madunix (Jul 23, 2013)

bump??


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## Mk4jettablkonblk (Aug 15, 2021)

thejordan said:


> *Re: how do i bleed air out of cooling system? (Andaloons)*
> 
> thermostat and/or waterpump.
> whats your mileage?
> ...


Car only over heats at idle and it doesn't over heat if heat full blast and ac blows hot what can be wrong


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## Vegeta Gti (Feb 13, 2003)

start searching Sir first post.....check the FAQ


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## Shinsti (Aug 13, 2021)

How is it going everyone,

I've been lurking the forums a lot, and recently got the same problem as many of here. Everything started with the engine overheating, so I would like to share my experience: I would like to add that i'm from the North part of Mexico, so around this time of the year we get 115-120F weather from May all the way to September, and I daily drive my car to work which takes a solid 20 minutes in that weather, mines a 1.8T 2003 Jetta GLS with a 5-Speed

Replaced the T-stat, making sure the fans turn on (with ignition ON and the A/C button ON as well, both fans should spin, to make sure both fans work first of all)
Still, it was overheating, so I got the radiator off and ran a hose trough the top hose until everything was clean, gotta say there was some nasty stuff coming out, so I thought that was the whole reason of it overheating.

Plugged everything back together, I used the bleeder hole in the heater core, but it was STILL overheating (even at idle). Defeated, I brought the car to my mechanic, and it turned out it was a broken water pump (I didn't know you could check the little upper hose in the expansion tank)

So, new waterpump, new timing belt and everything, as well new radiator hoses. Ran it for a few days, everything seemed sorted out, but after 2 days of daily driving, car was back at the overheating boogaloo, so I took it back to my mechanic and turned out the lower part of the radiator (close to the fan thermoswitch) was leaking, so I had air in the system.
Sent it to a radiator shop that my mechanic recommended, bought a new one, and they installed it.

Here's the tricky part: I go to pick up my car, and they are putting everything back together (front end, etc.), so I see that they're "purging" the system with expansion tank CLOSED, and i thought maybe they already burped it with the expansion cap open.

I drive back to my house which is like 15 minutes away from the shop and the car didn't overtheat. Everything seemed taken care off, until the next day.
I check my levels before any trip, cause I know level tends to drop because of the air bubbles, so that wasn't the reason of the overheating part, but I didn't check the "No heat" test, and that was it, air wasn't blowing hot at all, even when it's easily 110F outside and the engine was at operating temperature.
So I bypass the heater core with the help of some forum threads, *and I burped the system this way (take in mind that at this point the coolant level seemed fine/a little over the MAX mark):*

Jacked the car by the passenger side corner, put a funnel on top of the coolant ball so the coolant level doesn't overflow/the filling point is higher.
Started up the car
I picked up the expansion tank, undo the two screws on the back so I can lift it up higher than everything else in the system, and put a funnel on top so the coolant level doesn't overflow/the filling point is higher.
Got my brother to rev the car to 3k rpms, and *as soon as I lift up the coolant ball,* I hear a **** ton of popping, and the coolant ball level starts dropping, I basically added another 2 liters of G12/distilled water mix at the end of the burping process.

After that, *no more overheating.* I guess I had some air bubbles in the heater core, or it was rusted/clogged a lot, so that's why i bypassed it, and tbh, I don't even need heat in my town lmao, the lowest temperature point we get in winter is around 60-65F.
Just leaving this story in hopes someone else is getting some similar symptoms, or if you don't know how to burp it with the heater core bypassed.
Cheers and good luck, greetings from Mexico


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## Big_Tom (Aug 19, 2007)

Shinsti said:


> How is it going everyone,
> 
> I've been lurking the forums a lot, and recently got the same problem as many of here. Everything started with the engine overheating, so I would like to share my experience: I would like to add that i'm from the North part of Mexico, so around this time of the year we get 115-120F weather from May all the way to September, and I daily drive my car to work which takes a solid 20 minutes in that weather, mines a 1.8T 2003 Jetta GLS with a 5-Speed
> 
> ...


🍻


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