GM Full-Size Trucks 1980-1987 Repair Guide

Water Pump



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.

All Except 379 (6.2L) Diesel

See Figures 1, 2, 3 and 4

  1. Disconnect the negative battery cable.
  3. Drain the radiator and loosen the fan pulley bolts.
  5. Disconnect the heater and radiator hoses from the water pump assembly.
  7. Loosen the alternator swivel bolt and remove the fan belt. Remove the fan bolts, fan and pulley.

Click image to see an enlarged view

Fig. Fig. 1: Once the fan clutch has been removed, the pulley may be pulled from the water pump hub

  1. Remove the water pump attaching bolts, noting the bolt positions for proper installation. Once the bolts are removed, separate the pump and gaskets from the engine. On in-line 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.

Click image to see an enlarged view

Fig. Fig. 2: Access to some water pump bolts will require various length extensions

Click image to see an enlarged view

Fig. Fig. 3: Other water pump bolts may be removed using only the ratchet and a socket

  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.

Click image to see an enlarged view

Fig. Fig. 4: Once the bolts are removed, the water pump may be separated from the engine block

  1. Installation is the reverse of removal. Clean the gasket surfaces and install new gaskets. Coat the gasket with sealer. On fans which mount using bolts instead of nuts, a 5 /16 inch-24 x 1 inch 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. Torque the pump retaining bolts to 15 ft. lbs.

8-379 Diesel
  1. Disconnect the batteries.
  3. Remove the fan and fan shroud.
  5. Drain the radiator.
  7. If the truck is equipped with air conditioning, remove the air conditioning hose bracket nuts.
  9. Remove the oil fill tube.
  11. Remove the generator pivot bolt and remove the generator belt.
  13. Remove the generator lower bracket.
  15. Remove the power steering belt. Remove the power steering belt and secure it out of the way.
  17. Remove the air conditioning belt if equipped.
  19. Disconnect the by-pass hose and the lower radiator hose.
  21. Remove the water pump bolts. Remove the water pump plate and gasket and water pump. If the pump gasket is to be replaced, remove the plate attaching bolts to the water pump and remove (and replace) the gasket.
  23. When installing the pump, the flanges must be free of oil. Apply an anaerobic sealer (GM part No. 1052357 or equivalent) as shown in the accompanying illustration.

The sealer must be wet to the touch when the bolts are torqued.

  1. Attach the water pump and plate assembly. Torque the plate bolts to 18 ft. lbs. and the pump bolts to 35 ft. lbs.
  3. Assemble the remaining components in the reverse order of removal. Fill the cooling system, start the engine and check for leaks.