The Pontiac Aztec came equipped with the 3.4 liter V-6 engine. The water pump in this engine is mounted in a housing in the front of the engine and is a common cause of overheating due to leaks. Replacement of the pump is fairly straightforward and should take only an hour for an experienced home mechanic. The difficulty in this repair is in bleeding air from the system when refilling it with coolant after the repair.
Position a drain pan under the right front (driver-side) of the radiator and turn the plastic thumbscrew on the drain valve located on the bottom of the radiator. Unscrew the radiator cap and allow the cooling system to drain into the drain pan. Close the drain valve when the system is empty and coolant stops draining.
Loosen the water pump pulley bolts using a 10-mm wrench. Remove the serpentine by rotating the tensioner, located to the left of the water-pump pulley, using a 15 mm wrench to hold the tensioner while you slip the belt off the alternator pulley. It is not necessary to totally remove the belt from the vehicle. Remove the pulley bolts and slip the pulley off the front of the water pump.
Remove the 8-mm bolts that attach the water pump to the water-pump housing on the front of the engine, and pry the pump from the housing using a screwdriver. Clean the gasket surface on the pump housing using a scraper to remove all traces of the old gasket. Leaving pieces of the gasket attached to the housing can cause the new gasket to not seal properly and to leak.
Attach the new gasket (supplied with the new pump) to the new pump using gasket adhesive. Position the new pump in the water-pump housing and line up the bolt holes. This water pump will only line up one way and may take several attempts to line up properly. Install the 8-mm bolts to attach the new pump to the housing. Tighten the bolts securely. Position the water-pump pulley onto the new pump and install the 10-mm bolts. Reinstall the serpentine belt and tighten the pulley bolts securely. Check the belt alignment and adjust if needed by rotating the tensioner and slipping the belt into correct position on the pulleys.
Fill the engine with coolant by pouring it into the coolant recovery tank on the passenger side of the engine compartment. Open the bleed screws, using a screwdriver and a 7-mm socket and ratchet, to bleed the air out of the system. The bleed screws on this vehicle are located on the black coolant tube that connects the intake manifold to the thermostat housing on the opposite side of the engine. Add coolant until it pushes the air in the system out of the bleed screws and only coolant is coming out of the screws. Close the screws and start the engine. Test drive and recheck the coolant level in the recovery tank. Add coolant to the tank until it reaches the full make on the side of the tank.
