GM 91176915 Engine Coolant Pump

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A failure in the water pump can cause serious engine damage due to overheating. There are three ways to check the operation of the water pump while it's installed on the engine. If the pump is defective, it should be replaced with a new or rebuilt unit. With the engine running at normal operating temperature, squeeze the upper radiator hose. If the water pump is working properly, a pressure surge should be felt as the hose is released. Water pumps are equipped with weep or vent holes. If a failure occurs in the pump seal, coolant will leak from the hole. In most cases, you'll need a flashlight to find the hole on the water pump to check for leaks. The water pump weep hole will drip coolant when the seal on the pump shaft fails. If the water pump shaft bearings fail there may be a howling sound at the drivebelt end of the engine while it's running. Shaft wear can be felt if the water pump pulley is rocked up-and-down. Don't mistake drivebelt slippage, which causes a squealing sound, for water pump bearing failure.

Disconnect the negative battery cable from the battery. Drain the cooling system. If the coolant is relatively new or in good condition, save it and reuse it. Loosen the water pump pulley bolts. Remove the drivebelt(s). Remove the pulley from the end of the water pump shaft. Remove the timing belt. Remove the bolts and detach the water pump from the engine. Note the locations of the various brackets and the different lengths/diameters of the bolts as they're removed to ensure correct installation. Clean the bolt threads and the threaded holes in the engine to remove corrosion and sealant. Compare the new pump to the old one to make sure they're identical. Remove all traces of old gasket material from the sealing surfaces. Use a bead of RTV sealant to hold the pump gasket in place. Carefully mate the pump to the engine. Slip a couple of bolts through the pump mounting holes to hold the pump in place. Install the remaining bolts. Tighten them to the torque in 1/4-turn increments. Don't overtighten them or the pump may be damaged. Place new rubber seals between the water pump and oil pump and between the water pump and cylinder head. Reinstall all parts removed for access to the pump. Refill the cooling system and check the drivebelt tension. Run the engine and check for leaks.