A thermostat is considered to be faulty in the following cases: it takes too much time for the engine to heat up to operating temperature, but, at the same time, it overheats quickly, plus, the engine can boil if the thermostat gets stuck in the closed position. Remove the thermostat with the battery off. Next, remove the cover from the expansion tank, determine the location of the thermostat, after which remove all the elements that interfere with the operation, drain the antifreeze, and remove the thermostat. The thermostat is often located behind the throttle valve. Clean the seat and install a new thermostat.