How to Change the Water Pump of a 1998 Mazda B2500

The 1998 Mazda B2500 base model pickup truck came with a 2.5-liter four-cylinder and a five speed manual transmission. Your water pump is responsible for cycling the engine coolant through the engine, radiator, and heater core to help keep the engine at an optimal operating temperature. The water pump on your engine is located in the center of the engine just above the crankshaft and is driven by the by the serpentine belt. To remove the water pump you have to remove the cooling fan, fan shroud, and fan clutch. Your engine uses basic green coolant and has a total capacity of 7.2 quarts.

Instructions

Park the truck on a level surface and set the parking brake. Lift the hood and support it with the hood prop rod. Lift the front of the truck into the air with the floor jack and place the jack stands under the front frame rails of the vehicle. Lower the floor jack until the truck rests securely on the jack stands. Remove the floor jack and allow the engine to cool completely before continuing.

Turn the radiator cap a quarter turn counterclockwise to the pressure relief position and allow the system pressure to vent. When the pressure has been relieved, remove the radiator cap.

Place the drain pan under the right corner of the radiator below the radiator drain cock. Rotate the radiator drain cock counterclockwise and allow the coolant to drain into the drain pan. When the coolant has finished draining, close the drain cock. Remove the drain pan and store it in a safe place.

Remove the four bolts securing the fan and fan clutch to the water pump with the socket and ratchet. Remove the upper and lower fan shroud mounting bolts. Lift the fan, fan clutch, and fan shroud from the engine bay. Do not lay the fan on its side, as the clutch's internal fluid may leak and ruin the clutch. Pull the water pump pulley from the water pump hub.

Draw out a sketch of the engine pulley system and belt routing. Place the 3/8-inch breaker bar into the square hole on the end of the tensioner arm and rotate the tensioner counterclockwise. Slide the belt from around the tensioner and alternator pulleys and slowly release the tensioner to its natural resting position. Allow the belt to rest on the fan clutch.

Squeeze the pressure clamp for the lower radiator hose at the coolant inlet tube with the pliers and slide it down the hose about three inches. Pull the lower radiator hose from the inlet tube with a twisting motion. Remove the coolant inlet tube bolts with the socket and ratchet and remove the coolant inlet tube from the water pump.

Remove the three water pump mounting bolts with the socket and ratchet. Remove the water pump from the engine and set aside. Clean the water pump mounting surface on the engine block with the wire brush.

Inspect the new pump and gasket for any defects. Clean the water pump bolts with the wire brush and apply a coat of thread sealant to the bolt threads. Place a small dab of grease to the water pump impeller in three places, in-line with the pump mounting holes.

Position the new gasket on the water pump and set the water pump onto the engine block. Install the water pump mounting bolts and tighten to 15 to 20 foot-pounds of torque with the torque wrench.

Inspect the coolant o-ring on the inlet tube and replace as necessary. Apply a small amount of grease to the tube o-ring and set the coolant inlet tube into position. Install the mounting bolts and tighten with the socket and ratchet. Install the lower radiator hose to the inlet tube. Squeeze the pressure clamp with the pliers and slide it up the hose until it is about a half inch away from the end of the hose.

Route the serpentine belt around the engine pulley system according to the sketch made previously. Hold pressure at the tensioner pulley by hand and rotate the tensioner arm counterclockwise with the breaker bar. Slide the belt over the tensioner pulley and slowly release the tensioner arm to apply tension to the belt. Set the water pump pulley onto the new water pump fan hub.

Position the fan shroud, fan and clutch into a position that they can be lowered into the engine bay. Loosely install the upper fan shroud bolts. Loosely install the fan and fan clutch bolts to the water pump. Tighten the fan and fan clutch bolts to 12 to 18 foot-pounds. Install the lower fan shroud bolts and tighten all four fan shroud bolts with the socket and ratchet.

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

Fill the radiator slowly with fresh 50-50 green coolant and wait for the coolant level to drop as air evacuates the system. Continue to fill the radiator until the level holds steady at the base of the fill neck. Fill the coolant reservoir to the full cold mark.

Set the temperature control setting to the maximum heat setting and start the engine. Allow the engine to reach operating temperature. Continue to add coolant to the radiator until the coolant level stabilizes at the fill neck. Install the radiator cap and turn the blower control to the high setting. Warm air should blow from the heater vents and the upper radiator hose should be warm to the touch. Shut down the engine and top off the coolant reservoir tank as necessary.