Cummins isx air pressure in cooling system

I have exactly the same issue and we just did the combustion test and the fluid stayed blue no trace of green so no combustion gas
It's an 09 ISX that has been completely del€Ted.
How to test for the compressor?

 

for now the current solution was to drill a very small hole in the Overflow cap.
Coolant stays perfect now.
In the mountains going uphill with a heavy load I turn the fan override on so the coolant will not boil

 

Wow,! great fix there. That's a bandaid that will eventually just get ripped off.

 

I did something similar to my Pete with a cat and got a similar responce as swaan just gave haha.

Mine bought me a couple months but eventually blew out and when it blew..... it blew good!

 

I'm not trying to be a smart ### , just calling it as I see it.

Yes that's what happens , in the end the money you saved by jerryriggin it and running it longer gets absorbed by the extra cost when it really does blow. Usually ends up costing way more in the long run...
These is no doing it on the cheap in this business.

 

And it will hurt. More than your mom said it would.......lol

 

Easy it can leak and cause over pressuring of the coolant.,I had it happen. Shortly after the coolant mixed with the oil and inframe was here

 

Disconnect the lines from the compressor and push on accelerator pedal. If coolant still comes out coolant tank then it's head gasket possibly. If it doesn't then it's your compressor. My compressor ended up causing me to inframe my engine because it caused the o ring on the piston to move which allowed coolant to get in the oil