I have a '91 Toy 22RE 4X4 PU that has a weird overheating problem. The temp gauge stays absolutely normal (middle of the gauge range) all the time until I move the heater level up midway to full, then after about a mile or so of driving, the temp goes way up, not into the red zone, but 3/4 of the way up. Due to this, I've refrained from using the heater in the truck this winter. Fortuantly, I'm in Las Vegas, so our winter is mild compared to the rest of the country.. If I close the heater lever to off, the temp stays up for about a mile or so, then drops extremely abruptly directly back to the middle of the range, and stays there..I drove the truck from Las Vegas to Los Angeles at high freeway speeds last month, I think the cooling system is in good condition. Based on the abrupt drop back to normal, I'd kind of thought it might be the thermostat, but I'm not a trained mech, so it's just a guess.. What say the experts here on the group??
TIA dave daveATfrandinDOTohArGee