Oil contamination

JSHOE96

MEMBER
2008 AUDI S6
5.2L
V10
4WD
AUTOMATIC
111,360 MILES

I am a technician but have not been able to come to a conclusion on diagnosis for my issue. Vehicle has always been maintained and properly cared for has acquired a coolant leak into engine oil while the car was sitting for 6 months plus. Cooling system bleed oil changed and no leaks apparent car runs great no coolant loss and about a month or two later slow coolant loss with the vehicle off, going into oil pan again. Car has not been driven while two are mixed. Pressurized system drops from 15-10psi quickly, checked various coolant/oil exchange spots and could not hear much with stethoscope. Any help is appreciated.

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I have seen this from time to time. We need to test the head gasket when the engine is hot. Here is a guide that will help:

https://youtu.be/5zpNjYmmiYY

More then likely you have a head gasket that is starting to fail and it only opens at this point when it is hot so when you shut the vehicle off the coolant bleeds over because the oil pressure drops to 0 but the cooling system remains pressurized so it pushes coolant into the oil.

I would do the test multiple times if the first passes the blue fluid test.

Let us know how you make out. Thanks

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Saturday, November 7th, 2020 AT 7:21 AM

JSHOE96

MEMBER
2 POSTS

Thanks for the response, like I had said the vehicle had not been started when the leak is present prior to the car sitting for a few months. I understand coolant pressure> oil pressure at shut off. But it never went through the heat cycles to do that. Prior to carbon cleaning, intake manifold, and hpfp replacement(along with some other minor repairs) no coolant loss or coolant in oil. I have done every test besides combustion gas test. And checked all work that I had previously done. This will be my final piece of diagnosis for the head gasket with the combustion gas tester.

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Saturday, November 7th, 2020 AT 7:34 AM

KASEKENNY

MECHANIC
18,907 POSTS

Yeah. That sounds about right for this to be the issue. When all else checks out it normally is the head gasket. However, I have had people check compression and it passes because it was done on a cold engine. We expect that when a head gasket fails that it is just failed. But unfortunately with the metal expansion it can open one up until it is bad enough that it is there all the time.

Let us know what happens. Thanks

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Saturday, November 7th, 2020 AT 3:52 PM

Oil contamination

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