Mercedes s320 1998 engine oil going through the cooling systme - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 06-02-2012, 10:28 AM Thread Starter
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Mercedes s320 1998 engine oil going through the cooling systme

Hi everyone, I am new to the forum and I hope to help each other by sharing our experience.

I will provide some introduction to my issue and what I did so far and hopefully someone may have a clue as to resolve my problem.

I bought a Mercedes S320 LWB 1998 Petrol three weeks ago and after a week or so I noticed that engine oil has been flowing into the cooling system.

So I started by checking the oil cooler and it was fine (I took it out and brought it to a specialist to do a pressure test). Then I checked the radiator just in case as I knew that the gearbox oil is going though there but the radiator was brand new. (despite that I did a pressure test and it was fine). Then the only reasonable and most likely solution for the issue was the head gasket. So I took the head out and brought it to a specialist for a test. He said it was fine but it was a little bit warped in the middle and it needed to be machined. So he did that. Then I put everything back together with the hope that all was good and fine. But I was wrong!!!

I still have that engine oil going through the cooling system?

So here are my thoughts and I would appreciate any comments and tips.

Reasons for an engine oil to go through the cooling system could be the following:

1. oil cooler - it can not be it as I tested
2. head gasket - it can not be as I have changed it properly
3. cylinder head crack - may be as I heard that even if you tested there were few cases some specialist can not catch the crack
4. Cylinder head warp - it can not be as mine was a little bit warped in the middle where oil and water are close into each other into cylinder 1 and 6 only
5. warped cylinder block - i did not check it as I thought if the cylinder head is a little bit warped in the middle then the possibility for the block to be warped is small and even if it is warped that should also be in the middle and therefore this can not be a reason for my problem
6. a crack into the cylinder block - i am not sure here as i think that if the block is cracked I should see water into the engine oil and not oil into the cooling system.

I noticed that when I have changed the cylinder head gasket on the first start of the car I had a lot of pressure into the cooling system. The engine was running for 15 mins when the temperature of the water went to between 90 to 93 C degrees. I am not really sure what to think about it.

I have also noticed that oil is going to the cooling system only when the temperature is around 90 C and not less. That leads me to believe that I have a small crack somewhere probably into the cylinder head and most likely on cylinders 1 or 6 but the engineers said the head is fine. However I have heard for cases where a cracked head was not caught by specialist on the first test as that really depends on how the test is performed. Mine was done under 50 to 60 C for 30 min and the guy assured me that he is 100 percent sure that the head is fine.

As I want to repair my car my next step would be to test the cylinder head again by asking the engineers to do the test at around the 90C condition.

If the cylinder head is fine then the only reasonable explanation would be to have a crack into the cylinder block or a warped cylinder block however having said the logic above that seems to me unlikely.

Any help guys is much appreciated as I really straggle.
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post #2 of 2 (permalink) Old 06-04-2012, 06:44 AM
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