The 1998 Pontiac Sunfire water pump is located on the outside of the engine as opposed to inside the timing belt cover, making this one of the easier pumps to change. Several things could go wrong with the water pump---the bearings could go bad, thus the pulley won't turn the impeller and the pump won't pump water, or the pump could leak from the weephole or around the gasket area.
Slide the drain pan under the radiator petcock. Open the petcock and allow the antifreeze mixture into the drain pan. Close the petcock. Loosen the water pump pulley bolts, but do not remove them.
Loosen the belt tensioners on the accessory drive belts. Depending on the engine, you might have a serpentine belt and one or more V-belts, or you may have one serpentine belt. The serpentine belt uses a spring-loaded tensioner to keep it tight---push the tensioner away from the belt, using a socket, then lift the belt off the pulleys. For V-belts, loosen the adjusting bolt in the slider brackets and push the accessory (alternator, power steering pump) toward the engine, then lift the loose belt off the pulleys.
Unplug the wiring harness on the back of the alternator. Remove the main power wire from the back of the alternator with the appropriate wrench. Put the nut back onto the stud, so you don't lose it. Remove the alternator retaining bolts, alternator and alternator bracket with the appropriate socket.
Remove the water pump pulley bolts, then remove the pulley. Remove the water pump mounting bolts with the appropriate socket, then remove the water pump with from the engine. Clean the mounting surface on the engine with a screwdriver and a rag.
Line the water pump-mounting surface with a thin layer of RTV silicone onto the water pump. Place the gasket on the water pump and press it into the silicone. Install the water pump and tighten the retaining bolts to 19 foot-pounds of torque.
Reinstall the alternator bracket and alternator. Plug in the electrical connector on the water pump, then install the power wire. Tighten the nut for the power wire firmly. Reinstall the accessory drive belts. Refill the radiator.
