How to Replace the Water Pump for a 91 S-10 Truck

The 1991 Chevy S-10 base model truck was powered by a 2.5-liter four-cylinder engine with a manual five-speed transmission. The water pump is mounted to the front of the engine and is driven by the accessory belt. The fan and fan clutch are connected to the water pump shaft, and you must remove them when you replace the water pump. The 91 S-10 requires a 50-50 mixture of traditional green coolant and has a capacity of 3 gallons.

Instructions

Park the truck on a level surface and set the parking brake. Lift the vehicle hood and support it with the hood prop rod. Allow the engine to cool completely.

Turn the radiator cap counterclockwise one-half turn, to relieve cooling system pressure. Remove the radiator cap completely.

Lift the front of the truck into the air with the floor jack. Place the jack stands under the front frame rails of the vehicle and lower the floor jack until the truck rests securely on the jack stands.

Place the drain pan under the passenger side corner of the radiator, just below the drain cock. Turn the drain cock counterclockwise until coolant begins to flow out. When all the coolant has drained, close the radiator drain cock. Store the used coolant in a safe place until you can dispose of it properly.

Lift the truck off of the jack stands with the floor jack. Remove the jack stands from under the vehicle. Lower the truck to the ground and remove the floor jack.

Draw out a sketch of the belt routing on a piece of paper and set it aside for later use.

Attach the ratchet to the hole on the belt tensioner, rotate the tensioner clockwise and remove the accessory drive belt from the engine. Release the tensioner slowly until it rests in it's natural position.

Remove the bolts holding the upper fan shroud to the core support and lower fan shroud section with the socket and ratchet. Disconnect the clip holding the vacuum hose to the upper fan shroud, and remove the upper fan shroud from the truck.

Draw a line over the water pump pulley and the fan clutch with the paint marker. Place the fork-shaped tool in the fan clutch, into the access holes of the water pump pulley. Place the fan clutch wrench onto the fan hub nut. Rotate the hub nut counterclockwise with the fan clutch wrench. Remove the fan and fan clutch from the engine.

Remove the four bolts securing the water pump pulley to the water pump with the socket and ratchet. Use the fork-shaped tool placed in the pulley access holes to prevent rotation of the pulley. Remove the pulley from the water pump.

Loosen the clamp securing the lower radiator hose to the water pump and remove the hose from the water pump.

Remove the four bolts that secure the water pump to the engine with the socket and ratchet. Remove the water pump and water pump gasket from the engine. Clean the mating surface on the engine and the threads of the water pump mounting bolts with the wire brush.

Set the water pump and water pump gasket onto the engine. Install a coat of thread sealer onto the threads of the water pump mounting bolts and install the bolts. Tighten the water pump mounting bolts 21 foot-pounds of torque with the torque wrench.

Set the water pump pulley onto the water pump hub. Install the pulley mounting bolts and tighten them to 22 foot-pounds of torque with the torque wrench.

Attach the lower radiator hose to the water pump and install the pressure clamp.

Set the fan and fan clutch onto the water pump shaft. Line up the paint marks on the pulley and clutch. Tighten the fan clutch hub nut to 58 inch-pounds with the torque wrench attached to the fan clutch wrench.

Route the accessory drive belt around the pulley system as shown on the sketch you made previously. Hold tension on the belt by hand, near the belt tensioner. Rotate the tensioner counterclockwise and slide the belt over the tensioner pulley. Slowly release the tensioner and apply tension to the belt.

Set the upper fan shroud into position on the core support and lower fan shroud. Install the mounting bolts and tighten them to 89 inch-pounds with the torque wrench. Place the clip for the vacuum hose into the hole on the upper fan shroud.

Fill the radiator with fresh coolant. Start the engine with the radiator cap off. As the engine heats up and the coolant level drops, add more coolant to the radiator until the engine is warm and the coolant level stabilizes. Install the radiator cap. Inspect for any leaks and shut off the engine. Fill the coolant reservoir to the full mark with new coolant.

Take the used coolant to a local shop or parts store for recycling.