Cm2250 Air compressor or head gasket ?

[SIDE_SHOW]

Hello all I have a 2012 Pete with a cm2250 in it with 970k on it I parked the truck in February cause my dad had several strokes but before that I was putting maybe 1 gallon every 10k miles... in May I went and loaded in Houston and the light came on.. I didn't check the coolant before I left as I was in a hurry and forgot so I put 2 gallons in and I just figured it had leaked out while sitting and didn't think much of it headed to Kansas it was pushing 20 plus gallon a day out every time I would stop it would dump enough water out of the overflow for the light to come on I'd fill it back up and take off and all would be fine as long as i was running down the road till the next time I would stop and it would push out again... I checked behind the cooler and it was dry so I then put the overflow tube in a bottle of water and saw massive amounts of bubbles I figured it had dropped a liner so I deadheaded the truck home... Well last week I went ahead and checked the air compressor I plugged the intake and took off the hot line while the truck was hot and ran it and there was almost no bubbles whatsoever one small bubble every now and then so I thought hey maybe it's the compressor... so today I put a used one that I had around that is good and first thing I noticed was that on the old compressor if you turned the crank by hand it was very week and there was no pressure coming out of the hot line at all you could hold your thumb on it and spin all day but the truck built air fine? Also There was a small amount of pressure coming out of the coolant lines on the compressor while I was checking this. I put the new one on filled it up with water let it warm up and thermostats open and filled it up again and drove it about 50 miles and stopped about 6 times and it did not use a drop of water however there is still some pressure coming out of the overflow cap when I stick it in a bottle of water but nothing like it was its minewt now compared to before my question is how much pressure should be there and how do I check how much pressure is building at the cap? I put a brand new 16lb cap on it today as well there was a 23lb on it before that but it called for a 16 so that is what i put back on it... I just wanna make sure the truck isn't just acting nice now till I stick a load behind it and a driver in the seat and then all hell break thanks in advance