# Losing decent amount of coolant, but can't find the leak



## Currancchs (Feb 24, 2011)

Hi guys,

I am losing a substantial amount of coolant. About 1/2 gallon every 40 miles for 2 days.

A little background: This car has never leaked coolant, I flushed it a year ago and replaced with G12 (or G12 plus, but the correct stuff in any case) and have never added, but check frequently (usually check all fluids at every fill-up). I left the car sitting this summer for ~3 months due to work related travel, came back and had someone slash the top 4 days after putting her on the road. Got the top fixed by a shop (took ~2 weeks), and upon picking up the vehicle the low coolant light is on. I topped it off with some spare coolant I carry and drove it home.

Ever since it has been leaking a significant amount. The weird thing is is that there is no exhaust smoke, no sign of coolant in the oil, or vice-versa, she runs fine, no smoking from under the hood (I assume no coolant hitting something hot and evaporating for this reason) and no visible dripping onto the ground of coolant. I got underneath it yesterday, with the car running, and looked around for quite some time but couldn't see any leaks... The only thing I saw was some pink crustiness on a few of the oil drain pan bolts, towards the front passenger side, but after ~1 hour of idling and occasional revving/test driving and returning, not so much as a drop of any fluids on the ground... I am stumped here, I have no idea how I could be losing this much, but having such a hard time finding it... 

Any suggestions as to common areas to check or better methods of checking would be appreciated.

Thanks,
Matt


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## Scigano (Mar 10, 2011)

Try taking out your airbox to see if you can see any spilt coolant on the transmission or coming from any of the hoses or coolant flange on that side of the motor. 

The coolant flange is identifiable by coming directly out of the block and having the coolant temperature sensor coming out of it (easier to tell if you have the newer green-top sensor instead of the black). 

The plastic undertray may not allow the coolant to drip all the way down and pool on the ground for you to see.


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## Currancchs (Feb 24, 2011)

Hi there, thanks for your response. I don't have the factory airbox anymore, just a filter and heat shield, so visibility is good. I did take a look at the area you described, it seems a bit wet, but I have some oil leaks in that area, so hard to tell, but didn't look like coolant in that area. I also took the undertray off and still no signs of leaks... Car was actually on ramps idling and occasionally giving it some gas for ~1 hour, not so much as a drop of anything on the ground, including after coming off the ramps (thought it might be pooling somewhere). It definitely seems like its only really leaking under load. I believe I smell coolant when opening the hood after prolonged highway driving, not sure if this indicates anything in particular... If I figure out where its coming from I'll post back.


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## Beat the Heat (Apr 4, 2005)

Make sure it is not leaking from the passenger side of the engine. My water pump did not go bad but the o-ring for it went bad and i was leaking a significant amout of antifreeze and did not notice it at idle until it was to the point where id pull out of the driveway and the light would come on. It was leaking down the side of the engine all over the oil pan on that side.


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## Currancchs (Feb 24, 2011)

I think that that may be where my leak is coming from. I did notice some (a very small amount) pink/crusty residue on the passenger side oil pan bolts. Is there any good way to tell for sure if it is indeed leaking from there? I obviously don't want to take the timing belt/water pump off if unnecessary for diagnosis. I was thinking of taking a pressure tester to the radiator and seeing if I can see any visible leakage under that pressure (not sure if its higher than with car running or not). I did take the inspection cover for the timing belt partially off, didn't remove the charge pipe above, and the belt was dry.

The water pump/timing belt were replaced when I purchased the vehicle ~2 years/40k miles ago. I believe the dealer used a refurbished pump too... so might be time. (I had told him to use a metal impeller pump, but didn't want to make a huge deal out of it when I picked up the car and the receipt said refurb. pump.


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## 3Dachs (May 21, 2003)

Mine was leaking from the water pump. It would leak when the car was running, and it didn't matter if pressure had built. It got progressively worse over several days. Once I got the lower timing cover off, it was obvious where the leak was.


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## Scigano (Mar 10, 2011)

Oil leaking on the driver side of the engine can cause any of the o-rings and other seals in that area to deteriorate and leak (including the one for the coolant flange). 

Not that that is where your leak is coming from — but a new one can spring there if oil continues dripping there.


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## carfreak01 (Jun 13, 2009)

Currancchs said:


> The only thing I saw was some pink crustiness on a few of the oil drain pan bolts, towards the front passenger side


This pink crustiness is coolant that is leaking to the outside.
Around that area, is located the thermostat housing and a coolant line comming from the coolant reservoir, check those for any pink crust that could indicate a leak.
Also check the auxiliary water pump (mounted above the right fan of the radiator) this pump has two coolant hoses and they tend to leak, also this pump, internally is made out of plastic and it cracks and start leaking from the inside (this happened to me).
Remove the timming belt cover, and inspect for any leak in there.

If you are using only G12 coolant, then an indicator of a leak will be that pink crust.

Good luck


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## Beat the Heat (Apr 4, 2005)

Yea, good luck finding it. I waited too long to fix mine. I kept putting it off.


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## Currancchs (Feb 24, 2011)

Well, I took a look at it this weekend... Still no luck. Haven't been driving the car much because of this issue.

Looked at the thermostat housing, the after run pump, the coolant flange on top of the bell housing, as well as looking at the timing belt area... Couldn't see anything leaking definitively.

I had already bought a full timing belt kit with the metal impeller, but decided to get rid of my secondary air injection system/combi valve and reroute vacuum lines to get rid of the N112/N249, as I was having some issues with my SAI pump (rivets were missing) and both plastic lines connected to it were cracked. While working in this area it gave me a great opportunity to look more closely for leaks and I noticed two things that made me hold off on doing the timing belt:

1. There is a hissing noise from the coolant reservoir that is noticeable after shut down
2. Underneath the coolant reservoir it is pretty moist

Some or all of the moisture under the coolant reservoir could be attributed to spillage on filling, or overfilling and purging, but I figured for $20 (German Auto Parts) I would just replace the coolant reservoir and cap, just in case. I also read somewhere on these forums that if you run too much pure water in the cooling system it can boil over and purge itself. Due to the amount of coolant I've been going through I've been adding mostly distilled water, so it is pretty dilute.

In any case, my current reservoir has seen better days anyhow (yellowed) so I'll see if that does any good.

One last thing, when idling for ~3 minutes (waiting for fast food), I saw some steam coming from under the hood. Opened the hood and it was coming from middle front of the car, right near hood latch, this is the only time I've seen this happen, and it went away on its own after ~1 minute, was weird, not sure if this means my radiator's cracked or not... I don't think it has a radiator cap, just the reservoir cap. (Temp was


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## Currancchs (Feb 24, 2011)

Quick Update:

After getting back to my apartment today (drove another car to school), I decided to take another look at the TT. I unscrewed the coolant reservoir and started the car to see if there was any coolant leaking out of the reservoir itself, didn't see any. I then took it for a short (


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## forcefedjetta (Aug 14, 2003)

Are your carpets floating check your heater core


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## Yenrec (Dec 3, 2007)

having same issue and same area of leak on my car. Working on fixing it up, was in my brothers possession and its been trashed out. Leaking in same spot, and what did you mean by carpets floating?


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## Scigano (Mar 10, 2011)

Currancchs said:


> Quick Update:
> 
> I did replace the thermostat, but not the housing, about a year ago.


I've been told it's good form to replace both because the housings can get brittle with age, crack during disassembly/assembly, then leak afterwards.


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## forcefedjetta (Aug 14, 2003)

Yenrec said:


> having same issue and same area of leak on my car. Working on fixing it up, was in my brothers possession and its been trashed out. Leaking in same spot, and what did you mean by carpets floating?


I have seen heater cores fill the floor of cars the insulation under the carpets acts like a sponge till it gets saturated 


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## Currancchs (Feb 24, 2011)

Update: Issue resolved!

Thank you all for pointing me to common causes of issues such as mine. I finally got around to installing a new thermostat/o-ring/housing and coolant reservoir/cap yesterday. When removing the thermostat, I noticed that the bottom bolt was VERY loose... I had done the thermostat without housing about a year ago now, had never leaked coolant before... My best guess is that I just didn't torque it enough and it slowly loosened, but only when cold (just a guess, but would help explain why no drips when car was running on ramps) and in small enough amounts that I did not notice a puddle on the ground. For those of you that have done the thermostat before I'm sure that you can relate to how difficult that bottom bolt is to get to. I had to use a ~2 foot 1/4'' drive extension with u-joint to get at it, hard to get a good feel for torque with that setup... Not an excuse though. I used locktite this time around and made sure to tighten it pretty good this time, so hopefully no future issues. After doing the work I took the car on an ~2.5 hour drive with 0 coolant loss, checked this morning, level is still fine. I did make sure to get all of the air out before driving as well (idle with cap off and heat on full, adding coolant when necessary, had to blip the throttle a few times too to get good circulation through heater core, was blowing cold for the first few minutes, warmed right up after blipping).

Thanks again!


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## novae500 (Apr 27, 2012)

nice in finding the leak. I had one as well for the past few weeks. Would smell coolant when accessed the heater. Ended up being the y pipe that connects to the bottom of the coolant overflow tank. Picked up another one that came with the hose to the overflow tank and so far so good.


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## fabric8 (Jul 4, 2000)

*reviving an old thread for help*

my tt has developed a leak that sounds like what you described. here are some pics I took of my oil pan with pink crust drip marks



















I checked my coolant flange, reservoir and the area around where the water pump is (although I didn't remove the timing belt covers) and it all appears to be leak-free. I replaced my tbelt/h20 pump back in March at 70k miles, and I've just hit 75k miles so I'm hoping it's not the h20 pump that's leaking.

From these pics, does it appear the leak could be coming from the thermostat?


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## groggory (Apr 21, 2003)

fabric8 said:


> my tt has developed a leak that sounds like what you described. here are some pics I took of my oil pan with pink crust drip marks
> 
> 
> 
> ...


Could be lots of things. Looks like its somewhere around the thermostat housing though


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## fabric8 (Jul 4, 2000)

groggory said:


> Could be lots of things. Looks like its somewhere around the thermostat housing though


You were right! I decided to pull out the front plate that holds the oil dipstick tube in place to inspect the t-stat area, and sure enough, I found a pink pool of coolant crust right below the thermostat housing.










Can't believe this is leaking at 75k miles. My B6 A4 1.8t is at 115k and leak free. My B5.5 Passat 1.8t was at 128k when I sold it and was also leak free. My mk2 Jetta GL had 220k miles when I sold it and had no leaks! :banghead:

Anyway, for $18.10 shipped, I went ahead and ordered a new t-stat and housing.

Love the 'tex and it's helpful members for the past 14 yrs!


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