GM 3539588 Thermostat,Engine Coolant

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To remove and install the thermostat on 4.5L and 4.9L engines, start by draining the coolant below the thermostat housing. On some models, you may need to remove the upper air filter assembly. Then, remove the two bolts securing the upper thermostat housing to the lower housing and take off the upper housing. Next, remove the thermostat and O-ring from the lower housing. To install, place the new thermostat and O-ring onto the lower housing. Attach the upper thermostat housing to the lower housing and tighten the bolts. Refill the cooling system with a 50/50 mixture of water and antifreeze. Start the engine and check for any coolant leaks, allowing the engine to reach normal operating temperature before rechecking for leaks. For the 4.6L engine, follow similar steps. Drain the coolant below the thermostat housing and remove the front-end beauty panel and air cleaner if necessary. Remove the two bolts securing the thermostat housing to the intake manifold and take off the housing. Remove the thermostat and O-ring from the housing. Install the new thermostat and O-ring onto the housing and attach the housing to the intake manifold, tightening the bolts. Refill the cooling system with a 50/50 mixture of water and antifreeze. Finally, reinstall the air cleaner and beauty panel if they were removed. Start the engine and check for any coolant leaks, allowing the engine to reach normal operating temperature before rechecking for leaks.