How long can it take for a thermostat to go?

I replaced the thermostat in my 92 geo metro about 2 months ago, My car has started to overheat again, My radiator is completely sealed, and my cooling fan is working, i've taken it in to have it professionally diagnosed, and the best they gave me was fix the sensor, which i did, and to no change.



My question is, is it possible for a thermostat to go since then? as i did tell them that i replaced it recently, they could have overlooked it?
How long can it take for a thermostat to go?
Never assume that just because a part was recently repleced that it can't be faulty. Thermostats are mass produced and its not uncommon for a bad one to get through. You can easily test a thermostat with a cooking thermometer and a pot of wat and a stove. Put the thermostat in lukewarm water, put the pot on the stove and hang the thermometer in the water. Whatever the thermostat is rated for, it should open at that temperature (eg it will open around 195 degrees if its a high temp model. If the water boils (ie 212 degrees F) and the thermostat still hasn't opened, you can be guaranted its bad - it should open within a couple degrees of the rated temperature.
How long can it take for a thermostat to go?
You can run the engine with the thermostat removed. Take it out %26amp; see if it overheats. The only major job of the thermostat is to help the car warm-up faster so the heater will work quicker.

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