New here. Compressor??

[JO70]

Hello, I am new to the site. Not very knowledgeable on the technical side, just dumb enough to think I can figure it out. We have been chasing an issue for about 3 weeks now on an X15 CM2350 X116B. Can the compressor have failed and backfeed into the engine intake? No coolant loss per se, except one instance when the issue started about 3 weeks ago. Air dryer filter was full of coolant. Has not happened since.Truck runs great for a couple days, then it rears its head again. Driver has found that when the truck is starting to run hot, he can grab the cab air blow hose and release the pressure. He can literally sit there and watch the temp drop as he's releasing the air. Says air is coming out extremely hot. Anybody run into anything like this? New air dryer minus wet tank. New compressor discharge hose. Replaced numerous brake valves as we thought one was backfeeding. Didn't resolve the issue, but most were jammed up with gunk. No codes, except high temp.
Any help would be appreciated. Thank you