I have a 1988 Mitsubishi Mighty Max Pickup with the 2.6 Llter four cylinder engine with 165000 miles which heats up in hot weather under load but cools down well when not under load. It has a new radiator and catalytic converter. After I shut the engine off when it is hot there is prolonged bubbling from the radiator into the overflow tank. What should I be looking at for the causes of the excess heat and gas in the cooling system?
I would check the water pump next to make sure it is still pumping coolant through the engine. Also, how does your oil look? Any coolant in the engine oil? If so, you may have blown a head gasket. Possible bad thermostat too, lots of things to check, good luck!