Hi everyone. Short question: Why is my 2004 Paxton Supercharged Viper overeating? …water pump? …air in lines? …blown head gasket? …???

The background:

I have a gen 3 (2004) Viper with a Paxton supercharger on it. I purchased it set up as is about 1.5 years ago. It has been a pleasure to own and drive. I recently moved from MI to northern AZ (5000 ft elevation and about 20-30 degrees cooler than Phoenix in the summer).

The first time going up through the mountains, I noticed that the water temp gauge was starting to climb to the point the light turned on at 260. I immediately pulled over when the light kicked on and turned the car off to cool down. Engine temp never went much above 200-210. The water overflow tank appeared to be completely full. I waited until it cooled off and drove home, which was a quick drive (lots of downhill coasting) home. The water got back up to 235-240 on the way home.

When I got home I noticed that the power steering pump was making noise and steering was not as good. I checked the power steering level and it was completely empty. After researching it, I realized the power steering pump also runs the hydraulic fan. I got the car on the lift and after refilling the PS with ATF+4 fluid, I was able to find a leak at the hydraulic fan. I replaced the PS lines with braded lines from RSI. The car needed an oil change so I did that and also replaced the oil cooler lines with braded lines from RSI. I checked for leaks and did not see any. The hydraulic fan appears to be working properly and when the car is over 200 appears to be going very fast/appropriate speed. Since I had to take off the top radiator hose to replace PS lines I also turned the heat on in the car to make sure it circulated through.

I cleaned the car up and went for a drive. After 10-15 minutes the water was around 240-250 and I turned the car off. It appears that the coolant was boiling in the overflow reservoir. The engine temp was still around 200-210. I bought a different radiator cap from a local auto parts store which is a 16 PSI and placed it on the car. I drove back home (10 minute ride) and the car ran great with good power/boost. When I got home the car water was again 240’s and the coolant was now boiling and started spraying out of the new overflow cap. As the car sat there it literally boiled all of the coolant until the overflow tank was empty. The engine temp once again was around 200. I have not seen any coolant leaks whatsoever. I did remove the thermostat and it appears that it was replaced by the previous own and is a 170. I placed it in a pot of water on the stove and it does appear to be working correctly (opened round 175-185). The heater inside the car blows hot air. The upper radiator hose fills hot with fluid and radiator itself is hot.

So I don’t know what the problem is … was there air in the system? Water pump bad? Head gasket blown (oil looks great with no milkiness/residue)? I’m thinking my next step is to put everything back together, drain the cooling system, flush with water, refill with 50/50 and bleed the system. I’m hoping that will work.

I appreciate any thoughts/suggestions. Thanks!