Buick equipped the 2001 model-year Century Limited with a cooling system thermostat to control the circulation of the engine's coolant. While the engine runs, the thermostat remains closed to allow the engine to come up to operating temperature quickly. Once the engine reaches operating temperature, the thermostat opens, allowing the coolant to circulate and remove excess heat from the engine. A light or gauge on the dashboard warns you if an overheating condition exists. A malfunctioning thermostat can cause the engine to overheat.
Clean the mating surfaces of the water outlet housing and the intake manifold with a gasket scraper. The water outlet housing looks like a short pipe with a flange on the backside. The intake manifold's mating surface is on the front of the engine and matches the shape of the housing's flange. Remove all traces of the old gasket.
Insert the thermostat into the intake manifold with the domed end of the thermostat facing toward you. Seat the outer ring of the thermostat into the recess of the manifold opening.
Install the water outlet gasket and the water outlet housing over the thermostat with the gasket sandwiched between the housing and the manifold. Install two water outlet housing bolts and tighten the bolts to 18 pound-feet with a torque wrench and socket.
Slide the radiator hose onto the water outlet housing's neck by hand. Squeeze the tabs on the hose clamp together with hose-clamp pliers then slide the clamp into place on the neck of the water outlet housing. Release the hose-clamp tabs.
Seat the air cleaner housing into the two grommets on the front of the engine compartment. Install the powertrain control module (PCM) and harness inside the air cleaner housing.
Install the air cleaner housing's cover assembly onto the air cleaner housing and install two screws into the cover. Tighten the screws to 27 pound-inches with a torque wrench and socket.
Install the intake air duct assembly and tighten the clamps to 18 pound-inches with a torque wrench and socket.
Install the front fender upper diagonal brace. Install the brace's two bolts and tighten the bolts to 35 pound-feet with a torque wrench and socket
Close the radiator's drain valve at the bottom of the radiator. Pour a 50/50 ethylene glycol/water mixture into the radiator through the filler neck until the coolant level is up to the bottom of the neck.
Wait two minutes then recheck the coolant level. Refill with the 50/50 ethylene glycol/water mixture up to the bottom of the filler neck.
Install the radiator cap. Fill the coolant recovery reservoir to the full line. Start the engine and check for coolant leaks.
