[Steeveedee]

Generally, running hot at speed is blockage, like the radiator is clogged.
Generally, running hot at idle is from lack of air flow. Running hot in both regimes is what I had. After a lot of flogging, I put in a high flow thermostat. It's cooling fine, now. I run a 180º t-stat personally, also due to wanting to reduce heat soak. This truck had always started hard when hot, in the 40 years that I have seen it in operation, before and after the rebuild about 25 YA. Now I can repair the AC and use it. My didn't even know it has AC.