GM 91177756 Engine Coolant Pump

A faulty water pump can bring about dangerous overheating of the engine and there are 3 approaches of inspecting the functioning during it is fitted on the engine; if a problem is noted with the water pump, then a good unit whether new or refurbished should replace it. If the water pump is alright, when the hose is pinched just above the upper radiator, it should feel tight and when released the pressure should return to normal with a 'thud'. Water pumps have weep or vent holes which are used in the case of any failure of the pump seal, the coolant will always seep out of these holes and may be hard to locate from beneath the car using a torch. Furthermore, if the shaft bearings of the fan or water pump are burnt out, a loud whistling sound will be heard from the front part of the engine; the shaft wear can also be checked by moving the fan or water pump pulley from side to side-but one should not mistake it for slippage of the drive belt that produces a hissing sound, similar to a high-pitched squeal.