GM 10038439 Housing,Engine Coolant Thermostat

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The thermostat is essentially a valve limiting the flow of coolant driven by a temperature sensitive element. It is placed in a housing on the engine, which opens and closes at fixed temperatures to the coolant warm up or cool down the engine. Disconnect the negative battery cable first to remove the thermostat for examination or replacement. Open the coolant drain valve located on the bottom right side of the radiator and allow coolant to drain into a suitable container. If your car has cruise control and has a 1981 or earlier L4 and all V6 models, take out the vacuum modulator mounting bracket on top of the thermostat housing. The bolts that hold down the water outlet are removed from their position at this point. The thermostat can now be seen and pulled off from its location on top of an engine block. At this point, we should note how it is positioned in its recess as it needs to go back exactly like that when replaced. Before installing it, there should be no traces of old gasket left on both sides of a cover plate and around an outlet pipe edge; therefore, one must apply some force with such tools as gasket scrapers or putty knives to clean these surfaces up without dropping any particles inside cooling system passages. A small bead of RTV or similar sealer should be applied around the sealing surface on the thermostat housing such that it goes into its recess and stays there after placing thermostats properly. Next, immediately position another new gasket together with water outlet over it before tightening screws/bolts until correct torque is reached. When appropriate reattach vacuum modulator bracket to thermostat housing; connect negative battery cable then fill radiator with proper mixture of antifreeze and water. After starting engine without cap on radiator until upper hose becomes hot; when it's hot enough; open it with pliers making sure that you won't damage rubber hoses nearby while twisting them counterclockwise till they're removed from its slot or pull them slightly to obtain better visibility then remove upper radiator hose clamp by squeezing it together until metal tabs are no longer inside it. At this point, more coolant may be injected if necessary so as to reach the filler neck's topmost level. The radiator cap is installed with arrows matched up with the overflow hose. Those L4 models that were manufactured from 1982 onwards have a redesigned thermostat/housing for ease of serviceability. Firstly, take off the thermostat housing cap in order to replace the thermostat. After this handle has been pulled out, the replacement is situated by replacing the thermostat into the housing and ensuring there is a seat before putting on the cap again.

If the thermostat is suspect, it is more economical to merely buy a replacement thermostat as they are not very costly.

If excessive corrosion or damage is found on the thermostat, replace it with a new one.

If the thermostat does not check out OK, purchase a new thermostat of the same temperature rating.

For 1982 and later L4 models, the thermostat and housing have been redesigned for simpler servicing. To replace the thermostat, first remove the thermostat housing cap. Then, grasp the thermostat handle and pull it out. Replacement is completed by pushing the thermostat into the housing, making sure it is seated, and installing the cap.