454cid
Sooper Pooper
I had a thermostat in my '83 RX-7 stick closed once. I caught it in time and shut the motor down. I replaced it the next day.
When I was a Nissan dealer technician, a 4,000 mile Altima on the used car lot had a thermostat stick closed on a test drive. The salesman tried to drive it back to the dealership. It got so hot the distributor cap melted, which finally shut the car down. It got a new motor.
Those are problems with the thermostat itself, Though, which is not what Shurkey was saying. I too have had a thermostat fail closed. It was in my 4.0L 89 Jeep Comanche. More commonly, I've had them fail partially open. My Saturn and Volvo most recently.