GM 12559338 Thermostat,Engine Coolant

You can Select Your Vehicle to check if 12559338 fits your vehicle.

Begin by draining about three quarts of coolant from the radiator until the level is below the thermostat housing.

It is important not to drive the vehicle without a thermostat as it will cause the computer to stay in open loop, resulting in decreased emissions and fuel economy. Before condemning the thermostat, check the coolant level, drivebelt tension, and temperature gauge (or light) operation. If the engine takes a long time to warm up, the thermostat is likely stuck open and should be replaced. If the engine runs hot and the upper radiator hose isn't hot, the thermostat is probably stuck shut and should be replaced. If the upper radiator hose is hot, it indicates that the coolant is circulating and the thermostat is open. In cases where the engine has been overheated, there may be damage such as leaking head gaskets, scuffed pistons, and warped or cracked cylinder heads. To replace the thermostat, drain about three quarts of coolant from the radiator until the level is below the thermostat housing. Disconnect the upper radiator hose from the thermostat housing cover, remove the nuts/bolts, and lift off the cover. It may be necessary to move the belt tensioner bracket aside and tap the cover with a soft-face hammer to break the gasket seal. Take note of how the thermostat is installed, then lift it out. Use a scraper or putty knife to remove any old gasket material and sealant from the mating surfaces, being careful not to let any fall into the coolant passages. Clean the mating surfaces with lacquer thinner or acetone. Apply a thin layer of ATV sealant to the gasket mating surfaces of the housing and cover, and install the new thermostat in the engine with the correct end facing up. Position a new gasket on the housing, ensuring the holes line up with the bolt holes. Carefully position the cover on the housing and install the bolts, tightening them to the specified torque without overtightening to avoid distortion. Reattach the radiator hose to the cover and tighten the clamp. It is recommended to check and replace hoses and clamps at this time. Refill the system, then run the engine and carefully check for any leaks.