My brother's '96 has oil in the radiator, but no coolant in the oil. I'm thinking it's the oil cooler? I have had my share of issues over the years but never this. If my assumption is correct, how do you test it? Do you pull it out and pressurize it somehow? I don't even know what the thing looks like... is it easy to access? Is there a reasonable place to purchase one if it's bad? Thanks in advance for any help with this-

 

I have the same problem. Took my oil cooler along with radiator to the local radiator shop. The guy said he couldn't test the oil cooler......I don't know how a person would test it, the way it is designed. Some guys say the gasket itself can cause the problem....? I did find an oil cooler for sale for only $133 dollars, compared to cummins $315 . Look up "Diesel Specialists" online. Haven't ordered one yet....still trying to find a way to pressure test this one. But definitley take your raiator in to get flushed unless you have a hot water hookup to run through it. And cascade liquid dishwashing soap is great for flushing everyting when you get it put back together!

 

Could also be a head gasket.
High copper in an oil analysis usually indicates a blown oil cooler.

 

If it were me, I'd start by pressure testing the engine oil cooler. Just put you thumb over one of the oil ports and apply air pressure to the other port. Hold it under water and look for bubbles.



This is an old engine oil cooler next to a new one . . . .





It is immersed in the engine coolant inside the engine block, behind the engine oil filter mount . ..





Next to cylinders one and two . . .




They say washing the coolant system with Cascade dish-washing detergent works well.

 

Well I just pressure tested mine and it was ok...the gaskets weren't in the best of shape, so I'll replace those and see what happens. I also just got off the phone with Cummins and the guy said to check the O-ring and spring in the top of the oil filter housing- take out the bolt in the top of the housing and you'll see them.

 

Thanks so much for the help everyone. He lives a couple of hours from me... going this weekend to take it out and test it. This has always been a great site with good folks. Thanks again-

 

Welp...got everything back together......and now I have milky oil, "that I've just changed", And bubbles in the radiator! So now I get to replace the headgasket, oh well!