Some kind of Oil mixed in the Coolant tank....any idea?

[905084]

Only 2 things I know of that will put oil into the coolant:

A) Oil cooler is broken $$

B) Head gasket $$$$$

Might want to check the compression on all 8 cylinders. If one is zero, I'd lean to the head gasket.

[TozoM8]

1,) The oil cooler is a double jacket unit. Oil inside and coolant outside. If it has a hole, it will push oil into the reservoir because the oil pressure is greater than coolant pressure. However when you turn the car off there is no oil presure, but there 10-15 lbs coolant pressure that will push coolant into the oil.
2,) one of the trans cooler is integrated into your coolant radiator. Sometimes they brake into each other and the greater trans fluid pressure will push fluid into the coolant. With engine off you will have the same scenario as the oil cooler. If there is coolant in the trans you will need a rebuild. Coolant dissolves the clutch material realy fast.
3,) blown head gasket.

[NSU RS6]

I am trying to imagine the potential of this problem, and then multiplying by $3.

Makes ya want to squeeze your buttcheeks together.

[coco]

1,) The oil cooler is a double jacket unit. Oil inside and coolant outside. If it has a hole, it will push oil into the reservoir because the oil pressure is greater than coolant pressure. However when you turn the car off there is no oil presure, but there 10-15 lbs coolant pressure that will push coolant into the oil.
2,) one of the trans cooler is integrated into your coolant radiator. Sometimes they brake into each other and the greater trans fluid pressure will push fluid into the coolant. With engine off you will have the same scenario as the oil cooler. If there is coolant in the trans you will need a rebuild. Coolant dissolves the clutch material realy fast.
3,) blown head gasket.

Thanks, Tozo

Your explanation is easy to understand, thank you.

So the case 1) scenario, need oil flush and oil cooler replacement. Do the Bufkin pipe replacement at the same time (the aluminum pipe sold at e-bay, right?)
case 2), replace transmission cooler and trans rebuilt.... Is it possible to flush trans and replace with new ATF?
If not, should I do the T/C replacement with stronger T/C? Which is better? Anyone?
case 3) scenario, replace head gasket and do oil flash and replace oil filter and oil.

In each case, are there anything that I should do other than above?

Best regards,
Coco