oil in radiator 3406e

Cheap stuff FIRST

 

I had bunch of gray black goop in my radiator shop checked oil cooler and it was ok so they did injector o rings waters been clean since April

 

Usually in a Cat injector orings will cause fuel to leak into the oil. If you have fuel into the coolant the injector cups are the normal culprit.

 

I'm going to side with the oil cooler as well. Like superhauler stated oil pressure is higher then water when running. However when shut off rad pressure will stay at 15lbs or what ever cap pressure is and oil will be zero so you might get small amount of coolant in oil. I know some dealers will have a tool to pressurize the water side of cooler and submerge it in water if bubbles its toast. However if its not you just paid them to remove and install. Still cheaper then tearing engine down and hopeing.

 

oil in raditor will get worse if not corrected,water loss is another can of worms,could be a head gasket or external leak,hose clamp,bad hose.pressure test the cooling system while engine is hot,look for external leaks.common water loss is either head gasket or cracked head both are easy to find,i would take off intake manifold and there will be a sign of water loss..then have oil cooler checked

 

I have 2000 Western Star that I have changed the oil cooler three times in last three years . Just replaced it again 6 months ago and it puking oil out of the water over flow again! Where in the head would oil be pushed into the water ? and wouldn't it show signs in the running of the motor if the head gasket leaking or the head was cracked?

Thanks Doug

 

A pinhole in a cylinder, at just the right place , can put oil into the coolant. The piston/rings force it through while the engine is running. May or may not leak coolant into the oil also.