Tech Tip: ASC Reminds Technicians that Mazda Water Pump Twins are not Identical

Tech Tip: ASC Reminds Technicians that Mazda Water Pump Twins are not Identical

When referring to a catalog, whether OEM or aftermarket, a technician will find two different part numbers for a water pump for the Mazda MPV V6 3.0 liter: one for model years 1989 to 1995 (Pump A) and one for model years 1996 to 1998 (Pump B). No problem, right? Where the problem lies is the transition between 1995 and 1996 models where the vehicle could be equipped with either pump. If the wrong pump is installed, it can lead to a big headache.

Certain vehicle makes and models can make replacing a water pump a real challenge. This is one such example.

When referring to a catalog, whether OEM or aftermarket, a technician will find two different part numbers for a water pump for the Mazda MPV V6 3.0 liter: one for model years 1989 to 1995 (Pump A) and one for model years 1996 to 1998 (Pump B). No problem, right? Where the problem lies is the transition between 1995 and 1996 models where the vehicle could be equipped with either pump. If the wrong pump is installed, it can lead to a big headache.

The water pumps for these model years are nearly identical in appearance. The major difference is the diameter of the bearing shaft. Pump A’s bearing shaft pilot for the fan clutch is 17 mm in diameter. Pump B’s bearing shaft pilot for the fan clutch is 19 mm in diameter. When the incorrect water pump is installed, the headaches begin. If Pump B with the larger diameter shaft is installed when Pump A should have been used, it will not be possible to install the fan clutch. The water pump will need to be removed, causing downtime, aggravation and a water pump that cannot be resold. If Pump A with the smaller diameter is used where Pump B should have been, the smaller bearing shaft will not align properly with the fan clutch pilot hole and can be tightened off center. The misalignment can cause an out-of-balance condition.

When the fan clutch is off balance, it can be catastrophic to the water pump, engine components and the vehicle itself. The imbalance can result in damage to the water pump including bearing shaft breakage, separation of the hub from the bearing shaft, a cracked or shattered water pump housing, and/or premature seal or bearing failure. The car’s radiator, fan assembly, fan clutch, shrouds and even the hood can all suffer extensive ruination as well.

To avoid these problems, the installer should double-check the water pump and fan clutch applications, paying specific attention to the production month. Also, it is important to verify that the fan clutch pilot and bearing shaft diameters match within .5 mm.

For information on this and other water pump applications and installation procedures, including three-dimensional product views, visit the ASC Industries Inc. website at www.asc-ind.com.

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