how can you tell if the thermostat on your car isn't working?

Answer 1

The heater or defroster blows cold air.

Answer 2

They usually leak when they're bad and the engine doesn't get hot enough. You can take the radiator cap off when the engine's cold and watch for coolant flow as it warms up. There shouldn't be any movement through the radiator until the engine is hot.
The heater won't be cold. Just not as hot as usual.
That dropping them in the bucket to test them is about the dumbest thing I ever heard. Those things cost about $4 apiece and it would be crazy to put an old one back in anyway after you've gone through all the trouble of getting it out.

Answer 3

http://autos.yahoo.com/maintain/repairqa/fluids_heat_air_conditioning/ques018_2.html

see thermostat checks, NEVER take the cap off the radiator of a hot engine though!!!!!!!!!!!!!!!!! Or you might get scalded.

water pump might be shot too, this is another possibility, its located at the front of the engine and is driven by an engine belt, if its going, you might be able to hear it making noise, also the pully on it might wiggle up and down, try to wiggle it with the engine off. Thank GOD within 5 to 10 years we will all be driving Electric Cars. It's almost a certainty. 1st Hybrids, then PHEVS, then all Electric and then Fuel Cells.

Answer 4

Place thermostat in hot water if spring doesnt open it is no good. if its still in place, on car your car will usually overheat or your heater may not provide enough heat,also water may run out of overflow hose.

Answer 5

Pull it out and drop it in a bucket of boiling water. If it opens, put it back, if it doesn't open buy a new one.

Answer 6

It will not put forth heat or defrost the windshields in the morning.

Answer 7

usually the car will overheat

Answer 8

2 ways:

car runs warmer than usual.

OR

long time to warm up when you first start it.