Oil in coolant + Leaking pure coolant water!

[Rubba]

This morning i was changing the low beam H7 bulb and i saw the coolant level at minimum so i decided to top it up,
When i removed the cap i saw this


Dipped my finger inside the reservoir and there was a heavy oil.


The car runs fine no misfire no rough idle no overheating.

There also a leaking of pure coolant water under the G62 tube


At first i though it was a failure of oil cooler or oil cooler lines until i saw the leaking.
Any ideas about what it could be?

[gtsingh91]

Coolant flange is leaking, common failure. As for the oil in coolant that could be a bad oil cooler or head gasket failure.

[Spike00513]

Coolant flange is leaking, common failure. As for the oil in coolant that could be a bad oil cooler or head gasket failure.

Wouldn't it be 'oil cooler' because it's black?

I heard 'head gasket failure' would make it brown/peanut butter colored.

[Rubba]

Coolant flange is leaking, common failure. As for the oil in coolant that could be a bad oil cooler or head gasket failure.

I don't think it's a gasket failure, if it was the rpm's would go up and down when idling.
Also the engine oil is good, no water.
But the real question is... how there is no coolant in the reservoir but there is a pure water leaking? And the car is sitting from the last night.

[Rubba]

Wouldn't it be 'oil cooler' because it's black?

I heard 'head gasket failure' would make it brown/peanut butter colored.

Oil color appears as black but it's brown.

[A4SoftWalker]

A head gasket leak that bad would definitely have driveability/running issues. Although depending on how the gasket might have failed the oil pump might be pressurizing your coolant. Stranger things have happened.

Are you blowing coolant out your exhaust in the form of visible steam or coolant smell?

Personally I would be looking at the oil cooler.
Its been known to fail before on these cars. Its relatively easy to check. Be prepared to change both your oil and coolant. Also you should flush out your coolant system.

[Rubba]

Are you blowing coolant out your exhaust in the form of visible steam or coolant smell?

After 4 month of not running the car and after changing my cylinder valves and running the engine there was a white smoke but it disappeared after a while.

[5ktq]

you have a 2.0 dont you? i dont know if those even have an oil cooler

[A4SoftWalker]

Seeing that the 1982-2004 Jetta (clicky) used the same oil cooler and those were non-turbo cars I would give an educated guess that there is an oil cooler there.

This is what it looks like...


Also some reading indicates that the coolant is MORE PRESSURIZED than the oil so an oil cooler leak will leak coolant into oil. However, a head gasket leak is more likely to leak oil into coolant. Clint's writeup on a B5 (clicky) but all info is relevant. Depending on how the leak manifests it is still possible to be in the oil cooler especially seeing your accident might have affected the side of the car with your oil cooler.

[Misanthrope01]

^Id bet on oil cooler. A thin membrane keeps the fluids separate and its actually a heat exchanger from the diesel motors to keep their oil warm (diesels run cooler) just so happens to help get oil back down to operating temp on the gas engines. Long story short its a POS... I havent seen a head gasket fail on a 1.8t (OEM at least) seen the head crack personally, and it wasnt overheated or beat on...too hard at least.

^and coolant pressure higher then oil pressure??? sounds like real problem there.... coolant rez cap should purge off anything over ~11psi I believe. oil pressure should be much higher then that.

[Chemmie]

^Id bet on oil cooler. A thin membrane keeps the fluids separate and its actually a heat exchanger from the diesel motors to keep their oil warm (diesels run cooler) just so happens to help get oil back down to operating temp on the gas engines. Long story short its a POS...

No membrane in the proper sense- just a stamped can, all surfaces internal and otherwise being ignorant 18ga Al. Heat exchanger is all it is, exactly. Doesn't benefit gassers or oel burners any differently depending on the reference frame, either. Whole point is to get T_oil = T_coolant. Emissions regs being what they are, the faster you can achieve steady-state the better.

[Rubba]

you have a 2.0 dont you? i dont know if those even have an oil cooler

Yep 2.0
Here is mine

[Spike00513]

not sure if my memory is correct,
and maybe walky will chime in later to correct
but I think he didn't have leaking head gasket until a whopping 281k miles, on a B5 1.8T.

so there's that.

But I HAVE seen this before at under 150k-mi and was under the impression that it's 'oil cooler'.

I havent seen a head gasket fail on a 1.8t (OEM at least) seen the head crack personally, and it wasnt overheated or beat on...too hard at least.

I heard that old American cars had some tougher parts that had to be machined, namely steel cylinder heads, that were overbuilt.

And that in their eyes (the enthusiasts of those cars), aluminum is seen as cheap and disposable.
unless it conducts heat better?
I wonder if that has anything to do with it, or if it even matters, so long as the car isn't overheated.

But don't people here say that it's only a matter of time before AMB heads crack, before people decide to replace it with a certain B5 head which I guess does not crack?

I digress. Maybe that is a different topic.

[A4SoftWalker]

^Id bet on oil cooler. A thin membrane keeps the fluids separate and its actually a heat exchanger from the diesel motors to keep their oil warm (diesels run cooler) just so happens to help get oil back down to operating temp on the gas engines. Long story short its a POS... I havent seen a head gasket fail on a 1.8t (OEM at least) seen the head crack personally, and it wasnt overheated or beat on...too hard at least.

^and coolant pressure higher then oil pressure??? sounds like real problem there.... coolant rez cap should purge off anything over ~11psi I believe. oil pressure should be much higher then that.

True I stand corrected as I did not give enough explanation to my info. I will amend my quote with examples. The best troubleshooting method is to rule nothing out.

1) Oil pressure is higher than coolant pressure when the engine is RUNNING. Shut the engine down THEN coolant pressure EXCEEDS oil pressure in the system.
2) Depending on where the leak exists and how it manifests there is a possibility for the local area coolant pressure to exceed general oil system pressure.
3) A low coolant level observation is what the owner states prompted his finding this issue.

Everything else about this is routine. No need to repeat what needs to happen to fix this car. Oil cooler or head gasket is the problem. Thats about all us keyboard mechanics can tell we don't have the car in our possession.
The steam produced on starting the motor seems normal we cant smell anything over the internet. That is up to the owner

Also did you look at your dipstick?

[old guy]

^and coolant pressure higher then oil pressure??? sounds like real problem there.... coolant rez cap should purge off anything over ~11psi I believe. oil pressure should be much higher then that.

Just for clarification, the coolant reservoir cap blow-off pressure is 1.5 bar (22 psi).

[Rubba]

Oil cooler or head gasket is the problem. Thats about all us keyboard mechanics can tell we don't have the car in our possession.
The steam produced on starting the motor seems normal we cant smell anything over the internet. That is up to the owner

Also did you look at your dipstick?

As i said the engine runs very smooth, no smoke no misfire.
Yes i checked the dipstick and it's normal, no water or any other stuff.
I'm driving my C7 and the B6 is parked at the front of my house because this week is very loaded and i can't work on the car yet.

[A4SoftWalker]

It's possible you have more than one problem here as mentioned by gtsingh91.
Oil cooler failure - oil in coolant.
Coolant leak - low coolant level with visible leak.
Head gasket failure - low coolant level. Highly doubtful given that you found your leak.

Gluck with detection and repair.

[Rubba]

Here is the part, It's quite different from the turbo one
06B 117 021

[walky_talky20]

not sure if my memory is correct,
and maybe walky will chime in later to correct
but I think he didn't have leaking head gasket until a whopping 281k miles, on a B5 1.8T.

so there's that.

Walky here. A day late and a dollar short, as per usual. ;)

Yes, I did have an oil mixing issue, twice. Both times it was the oil cooler. I replaced the head gasket once for bent valves at ~200k, and once for the second oil/coolant mixing problem. Which just turned out to be the oil cooler AGAIN! I'm pretty certain I would have made it past 300k on the original head gasket if not for these other things.