Generally you have to take off the thermostat housing (where the top radiator hose attaches to the engine) you need to unclamp and remove the hose then the housing normally 2-4 bolts then it will be underneath. You can get a new one at any auto parts store.
Replace it.
If you question the condition of the thermostat, just replace it, they're cheap enough.
No
There's a gasket between the thermostat and the block that you need to replace.
1.2 hrs.
$150
Thermostat is most likely stuck in the open position; replace the thermostat.
no
replace it. when they go bad you can't fix them.
Drain the radiator. disconnect the top radiator hose from the engine. Remove the water inlet that the hose was hooked to. The thermostat is in the housing. Replace the gasket when replacing the thermostat.
probably a water heater.... {BMF}
Follow the upper radiator hose to where it meets the engine. Remove the two bolts of the thermostat housing and remove and replace the thermostat.