1988, Hilux, Non Diesel, 4Cyl 2.4L.

[StellarReality]

Hello, I have a 1988 Hilux and have been having a slight issue with the overheating. We had fixed the problem by replacing, the thermostat. All went well until my father brought to to me in Louisiana from Arizona, the whole trip he had to problem until he got it to me. When we ran it for a little while it began overheating, then the thermostat opened up and it cooled off. This is the third thermostat we have put in it. He had NO problems whatsoever bringing it across 3 states. We have had new belts, hoses, a new fan clutch, the cooling system was pressure tested for leaks and there were none. The thermostats seem to keep failing, we have just removed the thermostat and run it without one and there is no problem with overheating. What thermostat will not give me any problem, we have a fail safe one ordered and are waiting for it to come in. Has anyone had any similar problems?