OK so I just put new radiator tensioner pulley and other stuff on my 1997 Cummins a little over a month ago now I have oil in my radiator but the truck runs fine doesn't overheat or anything. What could the cause be???? I have only had the truck maybe three months and seems like one problem after another. Thanks in advance for any help

 

Could be a pin hole in the oil cooler

 

How do I check to find out if it's the oil cooler or the head gasket. I don't know much bout diesel this is my very first diesel

 

Ok

 

I've seen a lot of new parts come out of the box and be junk! It isn't unheard of for the engine oil cooler or tranny cooler to leak into the coolant. nothing sucks worse than replacing a part and it being junk. If you don't seem to have a running problem or overheating issue, probably a bad radiator.