99 cat C12 is pushing oil into the coolant

I don't have the answer but the title said I should reply so...........

 

Read it again. It says smartest…
Not smart@$$

 

Ohhhh! Sorry.

 

Ok……. Liner cavitation = oil in coolant

First off, cavitation is not very likely to occur on modern engines or those using Extended life coolant. But is common on neglected cooling systems using permanent “green” antifreeze that are not tested regularly for SCAs and or concentrated antifreeze mixed with undistilled water or just plain water added.

Cavitation tends to occur more on the hot side of the liner and toward the bottom of the cylinder where the o-rings seal the coolant from the crankcase. Which also happens to be near or below the bottom of the piston travel where the piston rings seal on the inside of the liner.

The candidate that I had that sticks out with this for me was a 379- 6NZ probably 10 years ago. Came in with the surge tank full of oil and all the hoses swollen. No runability complaints and no evidence of coolant in the crankcase or overfull. New CAT oil cooler, all new hoses and flushed the system many times with Cascade and new ELC went in. About a month later it’s back and guess what-oil back in the tank. Enough to say it was not residual. This time we had evidence of coolant in the crankcase. Condensation on fill tube though the oil looked normal and was not overfull. Dropped the pan and had coolant dripping on the inside of the liner with pressure overnight.

So, my theory is that it is possible that the oil from the cylinder walls or the crankcase can be forced thru a pin hole in the liner during operation. Logic would say that cooling system pressure would exceed crankcase pressure and it would not be possible. But I think the chances are unlikely that the cooler I replaced was actually leaking. After In-frame was completed I never saw the truck again.

This may have been a 1 off and I agree not common, but IMO possible.