Leaking Coolant mysteriously

tab2

Active member
Joined
Dec 21, 2004
TDI
2001 Jetta TDI
Need some help/ suggestions...
2001 with 160k miles (I ought it new in 2001), coolant was mysteriously leaking - appeared as the reservoir so replaced it, then some more leaking - looked like the coolant temp so replaced it (it was leaking slightly) - still leaking. No white smoke in exhaust (any more than usual), slight clamp on the reservoir, replaced. Still leaking. Does not leak on short trips, just the longer ones (20miles + ).
Brought to dealer in Florida (Tampa area) - after 3 hours, could not find it - going to check head gasket (Had to order a part for it) - I assume it is head pressure check. Dealer says hey suspect it is building up pressure and not releasing and running out the bypass
Any ideas or suggestions?
 

burn_your_money

Veteran Member
Joined
Oct 16, 2012
Location
Missouri
TDI
99 Beetle, 96 B4V, 05 Passat wagon
Do a cold pressure test on the cooling system and see what leaks show up. The engine needs to be as cold as possible for the best results. Also check your reservoir cap.
 

Caddy 16v

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Joined
Nov 6, 2011
Location
Hazelton, BC
TDI
2000 Jetta, 2000 Golf
Also check the coolant flange that goes into the head, there is an o ring under there that likes to leak slowly but surely. Took me forever to catch that.
 

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
If no bubbles in the coolant reservoir then not likely a headgasket issue.

What is the rate of leakage?

Does your car still have an EGR Cooler? Though you say you're not seeing what would be signs of a failed one of these, it's possible that it's got a small leak started (also would be prone to altered behavior due to thermal changes) and you can't really tell (yet).
 

tab2

Active member
Joined
Dec 21, 2004
TDI
2001 Jetta TDI
Thanks - cold pressure tested twice now for a couple of hours - no visible leaks to me (or the shop I had do another test to see if I was blind or not :) )
At operating temp, we have seen a few minor leaks oddly enough -

appeared to be the reservoir / Cap - replaced both
supply hose into the reservoir, if jiggled had a slow leak, put a hose clamp on it
Slight leak on the coolant temp sensor - replaced it - certainly have cleaned it and never had the heart to delete it but maybe I should - they are still available.


Interesting
"coolant flange that goes into the head, there is an o ring under there that likes to leak slowly" - will need to check it
"Oil cooler ,the O-ring may be leaking there" need to check that as well. If the O-RING was leaking, wouldn't that put oil in the coolant??
"EGR cooler" - Still in there - never replaced - maybe I should delete it, they are still available.

Rate of leakage - not 100% sure. The kid is driving it nowadays to college every day - it was leaking and he was not talking - just adding more coolant. Now that I am watching, it is not consistent - HOT or warm weather does not seem to make a difference, it appears that any long drives is when it leaks (45 minutes or more, combination city / highway). This car was purchased in Minnesota and ran awesome since day 1 with a few minor carbon cleans and other things - moved to Florida last year and this starts.

Had it to two shops and a dealer to find the leak -only confirmed what we have found so far - dealer is ordering a tool to check the head although I have to admit, I am not sure what it is, I was not there when the boy brought it in - I assume is is a pressure check of some sort. I thought about a chemical test I have read about but do not sure about those either.
 
Last edited:

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
Kids and cars... May never know what had happened to the car until it's torn apart!:eek:;)

Any chance that the engine overheated?

I think that the combustion leak test kits do work (I'd contemplated getting and using one on the daughter's wagon, but eventually kind of figured out my concerns weren't head gasket related). If there's a significant leak I'd think that you'd be seeing bubbles in your cooling system (cap off and running).

I'd not jump into yanking stuff (like EGR cooler) off. First figure out what the loss rate is; knowing this means that when you apply any fix that you can see what affect that fix has on the rate of fluid loss.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
A combustion products test will rule out, for the most part, a compression leak.

However, this sort of problem sounds a LOT like what I've run into in the past -- including on my vehicle (now my kid's.) Same deal -- small leak, can't find it, but it WAS showing up on the belly pan.

It turned out to be from the water pump shaft seal. Eventually it leaked badly enough that a pressure test found it and a timing belt replacement (with the water pump that was leaking) and the problem was resolved.

I suspected the EGR cooler too.... but I'm glad I didn't remove it without cause, since that would have been unnecessary work for no gain.

First rule of leaks is that small ones never get smaller.
 

tab2

Active member
Joined
Dec 21, 2004
TDI
2001 Jetta TDI
Yeah, I am an engineer - nothing really gets replaced unless proven or I think it is time anyway. On the Water pump, I do not see anything there and it was replaced 10k ago with the TB. Does not rule it out but...
Combustion test - may just do that to at least rule that out... Ordering today
 

djembeing

Active member
Joined
Nov 19, 2016
Location
KY
TDI
2000 Jetta GLS TDi
Check the coolant pipe behind the pump.

Sent from my SM-J327P using Tapatalk
 

Genesis

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Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
That too, especially if you've ever had a fuel leak from the IP. Leaking fuel eats rubber and that O-ring is in a bad place for leaking fuel to get trapped up against it....
 

seang28

Active member
Joined
Apr 10, 2011
Location
nomadic
TDI
2000 Golf 2D
I am running down this problem myself right now

Tab2 you mentioned a chemical test.
There is a dye you can add to the coolant which will expose external leaks by shining a black light on the engine.
Egr coolers tend to leak in these cars, blowing small amounts out the exhaust, which you wouldn't necessarily detect. There is a kit available from Id parts to bypass the coolant flow through the egr cooler while leaving it in place, retaining the emissions function of the
egr.
With the engine running, squeeze the upper radiator hose. If its soft, you're good, but if it is hard, the system is pressurized, either by a bad head gasket or leak in the egr cooler.
I have just installed the bypass kit in the hope the latter is true in my car.

Two years ago I ran into this problem and ended up replacing the head gasket to the tune of $1300, and here I am again.
 

CopaMundial

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Jan 30, 2011
Location
Southeastern PA
TDI
03 Jetta Wagon 5sp (New to me Oct 2014) 03 Jetta 5sp (RIP Aug 2014)
As was mentioned, leak detection dye and a black light will expose the location of any leaks.
Head gasket problems on stock ALH are pretty rare, especially if there hasn’t been some other earlier mistreatment (like running car out of coolant). If that were happening to the degree that would push coolant out of the reservoir then it would be more obvious than this.
 

tab2

Active member
Joined
Dec 21, 2004
TDI
2001 Jetta TDI
Thanks, I will try to look at those this weekend.

The dealership paperwork the kid has states: Performed multiple pressure tests and inspection - found no leaks under pressure, suspect excess compression build up in cooling system causing relief of coolant system resulting in coolant loss

NO running out of coolant ever, she has been babied (Until I turned her over to the boys so you never know or they would never admit it). This TDI has performed flawlessly since 2001 with the exception of the carbon build up when she was new, never since the change in fuel standards
 

AndyBees

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Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Sharing my experience with some suggestions

For what it is worth, I tapped the expansion tank on the ALH engine in my Vanagon for the use of a mechanical pressure gauge mounted at the dash. The system pressure very seldom reaches 10 psi (mostly between 8.5 and 9.5 psi).

Anyway, back in the summer of 2014, on the first day into a 33 day 11k mile road trip, the pressure hose split at the gauge (found the split after returned from the trip). This allowed the system pressure to drop to zero. So, rather trying to identify and repair, I just drove on for the next 32 days. The engine never over-heated, I never had to add coolant, and there were no leaks.

So, based on that experience, I suggest that you drive the car with the expansion tank cap loose. Drive it several days and observe the coolant level regularly. If the coolant level doesn't drop down, you can assume the leak you are experiencing is very small and requires system pressure to expel the coolant.

I seriously doubt the head gasket is the problem.

-Water pump
-Coolant flange below IP where the T-stat is located
-Coolant pipe that enters the Water Pump housing behind and below the IP (black metal pipe with O-ring)
-EGR cooler
-Oil cooler
-Heater core
-Coolant Temp Sensor O-ring
-Crack in radiator
-Coolant flange at the end of the head (below vacuum pump)

Combo of two or more of the above...
 

joep1234

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Joined
Jan 2, 2014
Location
NC
TDI
former '04 Beetle TDI, now 2x '15 Audi Q5 TDI's, 2007 Dodge Ram 4x4 6.7
Are you still running G12 or G13? Either one will glow under a UV light to help to detect them in leaks. Look at your small hoses on the back of the head. I recently had to replace the one that fed the egr cooler and didn't find it until we pressure tested it with a UV light. It was a pin hole that would let a drip every now and again.
 

PakProtector

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Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
Just one more that has not been mentioned yet. I just did them on mine. The two o-ring sealed joints at the heater core; trans side of the firewall, and diagnose-able with a dry finger. Get it warm and feel the lower side of the joint. They are likely fixable with just an o-ring replacement, but I never discovered what the exact size is. Besides, if I replaced the O-rings, the hoses would have failed immediately after...and I would have had to be more careful pulling the clips to tear them apart anyway...LOL
cheers,
Douglas
 

indysoto

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Joined
Mar 14, 2004
Location
Eugene, OR
Are you still running G12 or G13? Either one will glow under a UV light to help to detect them in leaks. Look at your small hoses on the back of the head. I recently had to replace the one that fed the egr cooler and didn't find it until we pressure tested it with a UV light. It was a pin hole that would let a drip every now and again.
Hopefully it's the pink stuff..X2 you can get a bad ass 100 Led AA black light off amazon for 10$ and shine it on all your friends clothes and embarrass them too ;)
 

tab2

Active member
Joined
Dec 21, 2004
TDI
2001 Jetta TDI
its the pink stuff - I will get alight, I did not know it would glow, that is awesome. As for friends and blacklights - my boys are 23 and 20, it will embarrass their mother when she asks questions - bonus points.. :rolleyes:
 

VChristian

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Joined
May 20, 2006
Location
Western NY
TDI
99.5 Jetta, (2) 02 Jetta, 03 Jetta, 15 Jetta
I am chasing a mystery leak which was an annoyance this summer, and only happened on cold days. Now it is a major river, and the outlet is on the oil pan, on the PAX side of the engine, just inboard of the timing belt area.

I thought water pump, so I added extra dye to the coolant, and watched. Sure enough, a river flows down the oil pan. So I pulled the top TB cover and looked with my UV light. Nothing. No where. Prybar on the water pump pulley, and it is solid. No dye splash in the TB area. None by the thermostat or the hard pipe near the injection pump.

Any other suggestions? The car is down, and I need to resolve this. The fortunate thing is that I cleaned the garage, so I am out of the snow and rain.
 

Genesis

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Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
I've had one leaking from the water pump SHAFT seal. The bearing was fine, so prying on it disclosed NOTHING. But that's where it was leaking from......

And yeah, it started as a minor annoyance, and then turned into.... well, The River Nile.

At which point it's "fix it now, damnit", which means a timing belt kit.
 

VChristian

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Western NY
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99.5 Jetta, (2) 02 Jetta, 03 Jetta, 15 Jetta
Genesis, was there any sign of splattered antifreeze inside the timing belt cover?
 

VChristian

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May 20, 2006
Location
Western NY
TDI
99.5 Jetta, (2) 02 Jetta, 03 Jetta, 15 Jetta
I poked around more this late afternoon, and do not see any leakage from the hard coolant pipe. Poking a UV light into the timing belt area, I don't see any splattered dye, but the area smells like antifreeze. Sticking one of those small cameras down as best I can, I can see that the backing surface is wet below the water pump, and there is antifreeze dripping down the oil pan. My take is that there is a 60% or better chance it is the water pump. The one in there is a Geba, and was replaced about a year ago, or 22K miles. The timing belt looks good, so unless I see that a bearing was washed with coolant, or something like that, I will swap in another pump.

I have had VWs for over 40 years, and can only remember once when I had to replace a water pump, and it was a bearing failure on this car. So in January, with what I remember was 10F weather, I did it outside. Probably the weather was 20F, but I seem to remember 10F which was probably the overnight low.

With 22K on the TB and bearings, I will just do the pump, unless I see some other problem that needs attention. The good news is that I have a complete TB kit, if I need it.
 

Genesis

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Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Genesis, was there any sign of splattered antifreeze inside the timing belt cover?
Not visible to REASONABLE inspection until I got it all apart. Then, yeah, but nowhere near as prolific as I expected. But from the top, with the upper cover off? Nope.

If it smells like antifreeze that's almost-certainly it... Once I got the lower timing cover off it was definitely moist down there.....
 

UhOh

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Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
Daughter's car had seen a WP failure with the PO. I didn't trust that the guy did a proper job on replacing everything, in which case I committed to doing a complete TB job. Good thing, as the idiot didn't replace everything. You could see the rust on the rollers from what had to have been the degradation of the WP that eventually went. Wasn't cleaned up well either. So, I actually took out a perfectly fine WP (it was the rest of everything that was suspect!). Story is here.
 
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