How to Change a Water Pump in a 1999 Trans Am

The 1999 Pontiac Trans Am was equipped with the modular, all-aluminum 5.7-liter V-8 engine, which actually displaced 346 cubic inches. It is the same Generation III LS1 engine that was used in the Chevrolet Corvette C5. When the bearings and seal in the water pump start to go bad, coolant will leak out of the weep hole in the back of the pump and you will notice coolant on the ground. Replacing the water pump in your Trans Am yourself will save you a considerable amount of money.

Instructions

Park the Trans Am on a level, paved surface and set the parking brake.

Remove the negative battery cable. Note if the Trans Am has the Delco Loc or Theftlock system, turn it off before removing the cable.

Allow the engine to cool. Remove the radiator cap. Place a large drain pan underneath the passenger corner of the radiator. Open the drain plug and catch the coolant in the drain pan. If your coolant is still clean, you can reuse it. Be sure to close the drain plug when finished.

Loosen the clamp that holds the air duct onto the throttle body. Unclip the air filter cover and remove the cover and air duct. Remove the bolts from the resonator and remove the resonator.

Remove the bolts from the upper radiator panel and remove the panel. Lift up on the cooling fan assembly and detach it from the tabs on the radiator.

Raise the front of the Trans Am with a jack and support with jack stands. Disconnect the fan assembly electrical connector from the wiring harness. Tilt the cooling fan assembly away from the radiator and lower it out of the engine compartment.

Attach a ratchet and socket to the bolt in the center of the belt tensioner and rotate it in a clockwise direction to remove tension from the belt. Thread the belt off of the pulleys and remove it. Remove the two bolts that hold the tensioner on the water pump. Remove the tensioner.

Loosen the hose clamps on the hoses on the water pump and remove them. Remove the thermostat housing bolts and remove the housing and thermostat assembly.

Remove the six bolts that hold the water pump onto the engine block. There are three bolts on each side of the water pump pulley. Tap the pulley with a wooden hammer handle to dislodge the pump from the engine block. Remove the pump.

Remove any gasket material from the engine block by scraping it with a putty knife. Be careful not to gouge the aluminum block. Clean the gasket surface of the engine block with a shop rag wetted with lacquer thinner. Remove the O-ring seal from the thermostat housing and discard it.

Spread a thin film of black RTV silicone on the gasket surfaces of the new water pump and engine block. Spread a thin film of black RTV silicone on both sides of the water pump gaskets. Mount the water pump on the engine block and install the six bolts by hand until finger tight.

Use a torque wrench and socket to torque the bolts to 10 foot-pounds, torque the bolts to 22 foot-pounds. Install the tensioner on the water pump and torque the bolts to 37-foot-pounds.

Install the thermostat assembly and torque the bolts to 132 inch-pounds. Reattach the hoses to the water pump and thermostat housing and tighten the clamps.

Follow the belt routing diagram on the shock tower to thread the serpentine belt back on the pulleys, working from the bottom up to the tensioner. Rotate the tensioner in a clockwise direction and slide the belt onto the tensioner.

Slide the cooling fan assembly up into the engine compartment, engaging the tabs on the radiator. Reconnect the electrical connector.

Mount the upper radiator panel and install and tighten the bolts. Mount the resonator and install bolts. Reattach the air duct and air cleaner cover, tighten the clamp on the air duct, and lock down the clips on the cover.

Raise the front of the Trans Am with a jack, remove the jack stands and lower it to the ground.

Refill the radiator coolant. If you have to add coolant, or replace it, be sure to get the right type of coolant, which is called Dex-Cool and is orange in color. Do not mix green and orange coolant.