Hi.

I have Chevy Express 2007 AWD with Vortec 5.3 LM7 engine. I have found oil in coolant - milky stuff below radiator cap. I discovered that mix oil-coolant was coming from little tubing (orange arrow on the photo, part # 533 and #536 on the diagram) which goes to the engine head. I dont see any coolanty in engine oil though. I didnt experience overheating, engine codes or excesive or low oil pressure. Nothing. Van was driving OK - I guess I just have found it before it could make a mess.

My question is what could be the issue:

1/ transmisiion cooler - maybe it is transmission oil in coolant but why I see oil/coolant mixure enetering from the tubing?

2/ blown head gasket - how to verify that? I did combustion leak test (suck air from top of radiator and checking if testing fluid goes from blue to yellow) with negative result. Seems the head gasket is not blown in cylinder area. Could be head gasket blown in oil passage? (case #3 on the first picture) letting oil to enter coolant? How can I verify that without removing the engine head

Thanks for any opinions/advice.

?

Thanks for opinions

 

Hello again.

That's the wrong head gasket in your picture. Yours looks more like this.


That milky stuff you show under the rad cap is known as the "Strawberry Milkshake of Death". Your tranny cooler is leaking into the radiator.

 

Thanks for help.

The head gasket of vortec 5.3 LM7 looks different that on e on your picture though. Can be seen here https://www.rockauto.com/en/catalog/...ad+gasket,5412 or on the picture below. There is place where engine oil can leak into the coolant. Still very unlikely though. I'll check that tranny cooler and hope that is the case.