Today my 4Runner started to over heat. I pulled off the road and thought the Radiator was low. After waiting for it to cool down I filled it and returned home. On the drive the gauge started to go up again. I turned on the heater and the temp dropped back to normal. At stop signs the temp agsain went up. Does this mean the thermostat needs to be replaced? Or???
Thanx
It sounds to me more like a leak so that you are losing coolant somewhere. First, look for an external leak. If this isn’t apparent, have a shop pressure the system (don’t drive it to the shop if it overheats–have it towed). When the engine is cool, fill the radiator with coolant, start the engine and look for leaks. Check especially around the water pump, but examine the hoses as well.
I would look for a few other things first.
Fan ot running
Radiator clogged inside or out
A leak
Bas head gasket
etc.