Engine Cooling System



4cylinder- 145,000miles original thermostat

new timing belt at 80,000 miles, new coolant 80,000 miles,

Problem 1: heater just wasn’t as blowing warm as it has always been and windows seemed to fog easily. The temp gauge wasn’t running at it’s normal range. Lower than normal. Cooling fans not running constantly either.

Action: Changed thermostat and refilled with same coolant but could not get last guart in radiator.Old thermostat looked galded on stem.

Problem 2: Test running to make sure new thermostat operating and coolant circulating. The temp gauge came back up to its normal position may be a little higher. Heater still not blowing as hot as it should. Top radiator hose, bottom radiator hose, and one heater hose at firewall not warm.

Question: Could the system be air locked somehow? Could the new thermostat be faulty? Could my water pump not be turning?


The fogging windows may mean there is a leak in the heater core. If you smell coolant inside the car that would not be good. There may also be a blockage in the core causing the coolant to not flow through it easily. Back flushing it may help fix that trouble. The water pump shouldn’t be a problem but there may still be a air gap in the system. Try to find a steep hill to go up and down on to see if that will purge the air. Filling the system through the top radiator hose may help also.


You mean you didn’t use new coolant? How old was the coolant?

Yes, there is probably air in the cooling system. That’s why the last quart won’t go back in. Some cars have a bleed valve to allow air to escape as the system is being filled.

You have to make sure the system has no air pockets.

Window fogging is often caused by running the heater with the system set to “recirculate.” Try setting it to fresh air and see if that helps.

I also suggest installing a new radiator cap along with the new thermostat.


I don’t know about this car, but many times it is easy to mistakenly put the thermostat in backwards. Do you recall whether or not you were attentive to and careful about that?