Hello everybody. I have a 1989 Sable with the 3.8 V6and 76,000 miles. I recently had the radiator replaced and now have a heating problem. The temperature guage heats up very slowly and then spikes all the way to the top and then comes down just as quickly. While all of this is happening the heater works and then doesn't work. I have checked the radiator to make sure that it is full and there areno leaks that I could find. Could it be a bad thermostat and if so is it hard to change?What else could it be? I would rather not take it back to the mechanic. Any ideas would be appreciated.

Sounds like thermostat that is not opening when it should. Cheap and easy first thing to try.

if tsat dont work possble start of headgskt problem which is common on this eng question does the eng run rough cold when first started?