ISX air compressor service life/ unloader valve

I've got a 2015 Intl with an ISX. It's an old Knight truck I'm working the bugs out of. So I've put a brand new air dryer on it, but the air compressor still has a habit of dropping very low, but only at idle, not while driving. I've run PB blaster through it like Cummins does with WD-40 to revitalize the reed valve, but either I didn't use enough or it's just worn out.

I guess my question is, should I rebuild the head, replace the head, or replace the whole compressor? It only has 535,000 miles, but just over 17,000 hours run time. I'd like opinions from those with more experience than I, thanks guys!

 

I was having the same problem, where I had to beat on the compressor, spray lube in the inlet etc, to get it to build air- always only a temp fix.

I finally just bought the head rebuild kit from Cummins for about $225, and rebuilt it. I had to pull the power steering pump and compressor, but it was surprisingly easy with basic hand tools. I must've scraped a good 1/4 cup of soot outta the head passages, but cleaned both halves really well, took out the unloader valve, cleaned it and lubed the o-rings, rebuilt it and used the torque specs in the manual, and not a hiccup since.