JABrx7

well lately my engine hasn't been running at its best so i went to check some of the fluids and when i opened up my coolant and there was a black oily film in my coolant. after seeing this i went and checked my dip stick and it wasn't milky. so im thinking that its rebuild time how ever i was thinking maybe the oil seals on my turbo went and its dumping oil in that way ? has anyone ever heard of anything thing like that ever happing?

RotaryVillain

Bad engine coolant seal is my guess. Both times in my life I've seen what youve described. Both times my engine had a bad coolant seal.

ColinRX7

The oily film is potentially not actual oil, it's carbon from the exhaust, it tends to look filmy when it's in the coolant.



I don't have much experience with the coolant/oil turbo, so I'm not sure what type of failure would lead to contamination.



Something else that leads to filmy residue in the coolant is deteriorating cooling hoses. Quite common.



However, a blown coolant seal on the exhaust side of the motor could be the problem.



You wouldn't neccessarily build up any excess pressure in the cooling system, and conversely, you wouldn't neccessarily lose that much coolant out the exhaust. The exhaust is under pressure but depending on the location of the seal being blown, the majority of the exhaust will flow out the port while some of it will get pushed past the bad seal into the coolant. There would be enough exhaust pressure to overcome the coolant pressure and enter the system, while not enough pressure due to the port being open to actually push real exhaust air into the coolant, just the filmy debris of burnt fuel/oil.



First place to start is to pressure test the cooling system and see if it holds pressure. If it holds pressure, I'd start looking at hose replacement and coolant change before anything else. If you come to find out you have to rebuild your motor, new hoses are a good practice anyways.