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REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6 and 7
Fig. 1: Remove the accessory drive belt(s)-on most models that means the single serpentine belt
Fig. 2: Once the shroud, fan and clutch or spacer are out of the way, remove the water pump pulley
Fig. 3: Disconnect the hoses from the water pump ...
Fig. 4: ... in most cases this means loosening the clamp and pulling off the hose ...
Fig. 5: ... but a stuck hose can be carefully cut away if you determine it should be replaced anyway
Fig. 6: Loosen and remove the retaining bolts, then remove the water pump from the engine
Fig. 7: Exploded view of typical Astro and Safari water pump mountings-note that some early-models use studs at various locations to help mount engine accessories
Disconnect the negative battery cable for safety.
Place a catch pan under the radiator, open the drain cock and drain the cooling system.
< >CAUTION <> When draining the coolant, keep in mind that cats and dogs are attracted by 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. Remove the accessory drive belt(s).
Remove the upper fan shroud and the engine cooling fan. For details, please refer to the procedure found earlier in this section.
Remove the water pump pulley.
Loosen the clamps, then disconnect the hoses from the water pump.
Remove the water pump-to-engine bolts. Because the bolt lengths and types may vary from location-to-location (some early-models may use studs in certain locations) on some models, tag or note all bolt locations as they are removed, this will help assure proper installation.
Carefully break the gasket seal and remove the water pump from the engine.
Using a plastic scraper, clean the gasket mounting surfaces.
For 2.5L engines, clean the water pump bolt threads, then apply a coating of GM(NNN) NNN-NNNNor an equivalent sealant.
Position the water pump to the engine using new gaskets, then install the retaining bolts. If any are of different lengths (or are bolts instead of studs) be sure they are installed in their original locations, as noted during removal.
Tighten the pump-to-engine bolts to 17 ft. lbs. (25 Nm) for the 2.5L, 22 ft. lbs. (29 Nm) 1985-92 4.3L engines, 30 ft. lbs. (41 Nm) 1993-95 4.3L engines, or 33 ft. lbs. (45 Nm) 1996 4.3L engines.
Install the hoses to the water pump and secure using the clamps.
Install the water pump pulley. For 1996 engines, tighten the pulley retaining bolts to 18 ft. lbs. (25 Nm).
Install the fan (and clutch or spacer assembly), along with the upper fan shroud. For details, please refer to the procedure found earlier in this section.
Install the accessory drive belt and check for proper tension. For details, please refer to the belt information in General Information & Maintenance of this information. SEE BELOW
Connect the negative battery cable.
Properly refill and bleed the engine cooling system, then check for leaks.
Belt replacement is a relatively simple matter rotating the tensioner off the belt (to relieve tension) and holding the tensioner in this position as the belt is slipped from its pulley. Depending on the engine and year of production, there are various methods of rotating the tensioner, but all require a breaker bar, large ratchet or wrench. Most early models use a tensioner which has a machined receiver which directly accepts a 1/2 in. driver. Most later models (through 1995) require that you use a large socket or wrench (usually 16mm or 5/8 in.) over the tensioner pulley bolt. A change was made to the part again in 1996, so the tensioner arm contains a machined receiver for a 3/8 in. driver from a ratchet or breaker bar.
Before you begin, visually confirm the belt routing to the engine compartment label (if present) or to the appropriate diagram in this section (if the label is not present). If you cannot make a match (perhaps it is not the original motor for this van), scribble your own diagram before proceeding.
Install the appropriate sized breaker bar, wrench, or socket to the tensioner arm or pulley, as applicable.
Rotate the tensioner to the left (counterclockwise) and slip the belt from the tensioner pulley.
Once the belt is free from the tensioner, CAREFULLY rotate the tensioner back into position. DO NOT allow the tensioner to suddenly snap into place or damage could occur to the assembly.
Slip the belt from the remaining pulleys (this can get difficult is there is little room between the radiator/fan assembly and the accessory pulleys. Work slowly and be patient.
Once the belt is free, remove it from the engine compartment.
Route the belt over all the pulleys except the water pump and/or the tensioner. Refer to the routing illustration that you identified as a match before beginning.
Rotate the tensioner pulley to the left (counterclockwise) and hold it while you finish slipping the belt into position. Slowly allow the tensioner into contact with the belt.
Check to see if the correct V-groove tracking is around each pulley.
< WARNING <> Improper V-groove tracking will cause the belt to fail in a short period of time. Connect the negative battery cable.