Internal coolant leak based on oil samples

Not sure, but I have seen this before with the potassium levels. I suspect the coolant is being burnt and potassium is the only element able to survive the combustion process and end up in the oil.

 

You have done the intercooler. The next cheapest thing is the oil cooler. We don't see too many Cats anymore. I have limited experience on those. I would still blame the oil cooler before a head gasket. Get a coolant pressure tester with a pressure gauge on it. Attach it to the coolant reservoir. Run the engine up to temp and see of the pressure rises too much, (15 psi or more). You can also have the coolant tested when the engine is running for the presence of combustion gases to diagnose a failed head gasket.

 

I think that is the best way to go. The source of the internal leak could also be a cracked block or head too, so there comes a time when you need to know when to walk away.

 

How can the coolant overpressurize if there is a 15psi coolant cap? As far as i know, what would happen is the air escaping the engine or from compressor would force the coolant out of the overflow tube. But pressure in the coolant system would still be at 15psi.

 

The coolant system will normally be around 7-10 psi. Once combustion pressure, or air compressor pressure enters the picture the pressure does go up to the pop off rating of the rad cap. At this point the coolant is over pressurized even though technically it never exceeded 15 psi. If the engine is pushing out coolant, there is a problem.