Cm2250 vacuum on coolant system?

[diesel607]

Thanks in advance for any advice or time you guys spend helping me.

I have a demandated cm2250. Has 582xxx miles. Using 1-1.5 gallon oil between services. It started pushing coolant yesterday into the overflow, got a low coolant light. Didn’t loose but a quart of coolant. Figured I had the start of liner protrusion and a head gasket. Got it home and put a pressure gauge on reservoir. It didn’t built the first pound of pressure but sucked the needle down below zero almost like a vacuum. I did blow a turbo seal about 3 weeks ago and hung a new vgt turbo. Been running fine, is it possible to have air pocket somewhere and it’s just now giving me fits?

I’ve checked transmission for coolant, took the back pipe off the egr cooler. I don’t know how to isolate the air compressor. No coolant in oil, no coolant in fuel tanks, no fuel or oil in coolant reservoir. I’ve also changed the relief cap on the overflow side. Truck is only running about 140-150 degrees while pulling 80k, granted it’s only 35-40 degrees where I’m at. When sitting at high idle it’ll come up to 190-200 degrees, it’s pushing more coolant at idle than while running down the road at 55-60 mph.

Is it possible that a water pump or sticking thermostat, injector cup, liner protrusion and head gasket, air compressor? Where do I start. I can’t find anyone that looks at me normal when I tell them I think I have a vacuum on my coolant system.