The 2003 Monte Carlo was designed to be a competitive entry into the growing market of high performance vehicles. Along with its counterparts, the Monte Carlo can be prone to overheating if the coolant circulation system stops working properly. Installing a replacement thermostat is usually the easiest fix to get the high performance engine back on the road.
Remove the bolts that hold the thermostat regulator housing onto the intake of the Monte Carlo with an 8mm socket. The bolts will be reused. Do not discard them.
Remove the thermostat regulator housing from the intake and push it off to the side. The radiator hose does not have to be removed since there is room to slide the hose and the housing off to the side.
Pull the thermostat out of the Monte Carlo intake, then pull the thermostat gasket off the intake manifold. Both can be discarded; they will not be used again. Inspect the mating surfaces of the intake manifold and thermostat regulator housing for any remaining pieces of gasket. Both surfaces must be clean for reinstall. If there is any gasket material left, scrape it off using a small metal scraper.
Place the new thermostat into the intake manifold and the place a moderate amount of RTV gasket maker on the mating surfaces of the intake manifold and thermostat regulator housing. Allow the RTV gasket maker to firm up for 15 minutes.
Bolt the thermostat regulator housing back into place using the original bolts. Tighten the bolts snugly so that radiator fluid does not leak out.
