All Chevrolet thermostats are made to control the internal temperature of your engine within a specified range. This is an automatic part that opens and closes by itself when operating properly. The manner in which the thermostat on your Chevrolet works is on the principal of metal contraction at specific temperatures. This allows for the coolant to flow thru once a certain temperature in the engine has been reached. All Chevrolet thermostats are located at the exit point of the coolant from the engine. A Chevrolet owner can locate this point by following the return or upper coolant hose from the radiator to the engine. Under the housing where this hose is attached, is the thermostat. There are three reasons for the replacement of this coolant part. The thermostat can be jammed shut, jammed open or is no longer working in the specific temperature range the engine requires. If it is jammed shut and your engine is overheating a simple solution to get your car to the repair shop is to force it open by jamming a screwdriver into it. By poking a hole in this device, coolant will flow sufficiently to make it a few miles down the road where a proper repair can be made. If it is jammed open or not operating at the specified temperature, your engine will have poor mileage and the heater in the passenger compartment will not be generating sufficient heat as it did before. Again replacement of this coolant part is required. When replacing a thermostat on your Chevrolet make sure you perform a hot water test before putting it into place on the engine. A very small percentage of thermostats from the factory are jammed shut and might not operate properly unless this procedure is done.