Losing Water and Running Hot

[Jpeavy314]

Looking for opinions, truck is in the shop but I want all the opinions lol. I have a 2007 Cummins ISX 400 ST. Ran warm on day 1, around 200-220 degrees water temp for 12 hours mostly. Day 2, ran hot, temps got up to 225-245 water and oil got up to 250-270. It’s losing water and I’m getting a low water alert on the dash after about 4-5 hours of operation. It runs perfect as long as the water levels stay up, around 190 degrees. I see absolutely no signs of water leaking from the engine on either side or the front, it’s dripping a tiny bit (maybe 2 drops per 60 seconds) from the overflow tube on the water reservoir. I have no white smoke from the exhaust, no loss of power, no water in my oil, and it doesn’t appear that I have any oil in my water. The water is definitely going somewhere. This truck has a new air compressor, new EGR cooler, new turbo, new rear main seal, new bell housing gasket, new clutch, fresh oil change, new air filter, new cam shaft, it’s been gone through with a fine tooth comb. After letting it sit and cool down after it heated up for about 3.5 hours, I filled it with water in the resivoir and started it it with the radiator cap off, the engine temp was probably 130-140 degrees. It immediately starting blowing water out of the top of the reservoir. I know this shows signs of the cooking system being pressurized. Do you guys think cracked head, head gasket, stuck thermostat, etc? I’m at a loss, if it were a head or head gasket I feel like I would have more signs, right? Thanks for your help! Truck has been de-mandated but still has Egr cooler