Help! I have a 1995 C220 with 139k miles (W202.022 chassis, 111.961 engine) with what looks like engine oil getting into the cooling system.

The thing starts and runs great and is in great condition. All stock, no mods, all standard options. Recently I replaced the water pump because it was leaking and squealing. The job went well. But when I initially drained the coolant, I noticed this layer of brown scum in the top of the coolant in the reservoir bottle. The layer was about 1/4 inches thick. I thought maybe someone put stop-leak in the system before I got the car (about a year ago). I drained the system and replaced the pump. I cleaned out the bottle and flushed the system twice before refilling with proper Zerex coolant and distilled water. Coolant was clear and clean. After a week I topped off the coolant and found the brown layer in the bottle again. I siphoned it off and topped it off. Now another 3 weeks and I see the brown layer is back and thicker than ever (about 3/4 inches this time). So, this is getting worse. I also notice that the oil level is down about half a quart after about 3 months and 4000 miles since the last oil change.

I am suspecting engine oil is getting into the cooling system. Is the head gasket my most probable cause? Or possibly the intake manifold gasket? Is this possibly a common issue on these engines? What can I do to prove it? Could this be transmission fluid? How do I tell for sure?

In my experience, when a head gasket develops a leak, usually coolant is forced into the crankcase as the cooling system is typically under more pressure than the crankcase. But I see no sign of white or creamy stuff on the dip stick. Is it normal for the crankcase to have higher pressure than the cooling system in this car? If no, do I have a secondary problem? And if so, how do I go about identifying the cause of pressure in the crankcase and relieving it?

Thanks in advance for any and all help you can provide.

 

Hi have you checked the gearbox oil level it could oil cooler in rad leaking

 

If you have an automatic transmission the radiator is used to cool the transmission fluid. A bad radiator will allow transmission fluid into the coolant (and probably coolant into the transmission fluid).


There have been posts in this forum and other one regarding this issue.

 

there is a oil cooler situated behind and fixed to the oil filter housing, if the rubber gasket has broken, oil will be forced into cooling system, I think one has to remove inlet manifold and associated pipe work to get to it, defitnately fun and games. good luck in resolving the issue.