Belts, Water Pump, & Fan Shroud Information

BELTS

Check that the serpentine belt is routed correctly around all the pulleys. Incorrect routing of the belt may result in the water pump turning in the wrong direction. An illustration of the correct belt routing for the application is on a label located on the fan shroud.

WATER PUMP

Check to see if the water pump is actually moving the coolant. This can be done by observing the coolant flow back to the radiator, by way of the heater hose, through the radiator cap opening. This check can only be made on a warmed-up engine (thermostat open). If there is no coolant being returned to the radiator, the water pump impeller may be slipping on the shaft.

CAUTION: THE RADIATOR CAP SHOULD BE REMOVED FROM A COOL ENGINE ONLY. IF THE RADIATOR IS REMOVED FROM A HOT COOLING SYSTEM, SERIOUS PERSONAL INJURY MAY RESULT. If the complaint is for an overheat condition on initial start of 4.3L, 5.0L or 5.7L engines, see GMC


Truck Service Bulletin (Corporate # 836001R). This bulletin describes the removal of a casting dam in the water pump.

FAN SHROUD

Check that the fan shroud is correct for the application and that it is not damaged (pieces missing). If the fan, fan clutch and shroud are correct for the application, the fan blades will be positioned partially (half way) inside the fan shroud and partially (half way) outside the fan shroud. In an incorrect assembly, the fan blades will either be too far inside or outside the fan shroud. When the blades are not positioned correctly, the fan will not be able to draw the required amount of air across the radiator, possibly resulting in an overheat at idle.