Losing coolant and air bubbles.

the cooling system is probably being pressurized by combustion gasses. Liner issue, head gasket, injectors are top contenders. Do not drive it any distance until you find out what the problem is. The longer you delay, the more damage will be done.

 

Head gasket most likely. The coolant coming out of the rad cap is usually a tell tale sign

 

I don’t know much about the egr cooler, but I think I’d prefer that over a bad head gasket. I do know, You can disconnect the discharge line from air compressor, carefull, loosen it first, let it bleed air out first, then remove it. Run Truck, if bubbles stop, air compressors bad. You also can pinch off the coolant hoses on air compressor, with flat vice grips, or loop one of the hoses, to the other on the block, isolating the air compressor. Either way should work. Don’t run it long without coolant circulating though, you’ll ruin a good compressor. Maybe there’s a way to isolate the egr cooler? I don’t know. But you want to eliminate any other potential source, before taking the head off. Usually a blown head gasket or cracked head, but not always.

 

cracked or scored cylinder liner. … very common to pre 2014 engines... or sunk liner .
if you will have cracked egr cooler you will have a coolant in egr pipes.. in the morning , before starting the engine, remove rubber hose that is on egr pipe and inspect inside...bad air compressor ? 0.1% of chances.

 

Run a sample of the oil that is in it now off to a mail order oil anil. place you can buy sample kits a truck parts store or T/stop, wait for it to come back to e/mail, If you know a shop that will pull the oil pan off and put pressure in rad. then they watch for coolant to drip out of liner pitting hole then turn eng. over 1/2 turn at a time till its been all the way around 1 turn, hope its just egr cooler bad letting ex. pressure in rad. most liners that have pitting will let oil get in rad.

 

What was your final outcome

 

You could get a kit to test for combustion gas in your coolant reservoir to try and rule out EGR or head gasket problems.

Combustion Leak Detector
Combustion Leak Detector Fluid

 

Best way to find out for sure is a pressure test. Test for leaks with 10 lbs of pressure, see if it holds. Start Truck, see if pressure builds. No more guessing.