GM Full-Size Trucks 1970-1979 Repair Guide

Water Pump



See Figures 1 and 2

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Fig. Fig. 1: Remove the water pump pulley ...

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Fig. Fig. 2: ... then unfasten the retaining bolts and remove the water pump

  1. Drain the radiator and loosen the fan pulley bolts.

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the heater hose and radiator. Disconnect the lower radiator hose at the water pump.
  3. Loosen the alternator swivel bolt and remove the fan belt. Remove the fan bolts, fan and pulley.
  5. Remove the water pump attaching bolts and remove the pump and gasket from the engine. On inline engines, remove the water pump straight out of the block to avoid damaging the impeller.

Do not store viscous drive (thermostatic) fan clutches in any other position than the normal installed position. They should be supported so that the clutch disc remains vertical; otherwise, silicone fluid may leak out.

  1. Check the water pump shaft bearings for end-play or roughness in operation. Water pump bearings usually emit a squealing sound with the engine running when the bearings need to be replaced. Replace the pump with a rebuilt or new pump (usually on an exchange basis) if the bearings are not in good shape or have been noisy.
  3. Installation is the reverse of removal. Clean the gasket surfaces and install new gaskets. Coat the gasket with sealer. A 5 / 16 '-24 x 1' guide stud installed in one hole of the fan will make installing the fan onto the hub easier. It can be removed after the other 3 bolts are started. Fill the cooling system and adjust the fan belt tension. Tighten the pump retaining bolts to 15 ft. lbs. (20 Nm).