I have a 1986 4runner with a 22re motor and ever since I replaced the head gasket I have had a problem with the thermostat...I think. When I first start the truck and drive it the temp gauge rises until it gets about 3/4 hot and then the thermostat opens and the temp gauge goes back down to normal within 30 seconds or so. I have tried three different thermostats but all three work the same. These were different temp thermostates too. I just replaced the water pump (it went bad) and now when the gauge goes up the coolant will push out of the overflow into the engine compartment until the thermostat opens. So my questions are..first why does the thermostat stick. Second the high temp reading I am getting, is that the actual motor temp or just the coolant temp at the thermostat housing (where the temp sensor is)? Third is the coolant being pushed out because I have air in the coolant system? I know this is a lot of info but if someone can give some advice I would appreciate it.
Thanks,
Eric

 

Have you searched 22RE temperature overshoot?