Auto Service World
Feature   August 1, 2002   by Auto Service World

Knowledge Building: Reducing Water Pump Comebacks

Water pumps are simple devices. All they have to do is keep coolant moving through the engine, the radiator and the heater core. It’s a simple job, but a critical one. And sooner or later, it is inevitable that they all fail; what’s not inevitable is that the replacement will fail soon after.

The fact that that does happen means that somewhere in the process something went wrong. One frustrating part of premature water pump failure is that it doesn’t occur immediately. Instead, it occurs just far enough down the timeline to cast doubt on just what the cause is.

Chief among the causes is failure to flush and fill the cooling system with fresh anti-freeze coolant. This is a cause that crosses the border of the DIYer and the professional technician. The issue is this: the contaminants that contributed to the failure of the first pump are dumped back into the system so they can do it all over again on the second pump.

Coolant should always be changed regularly. You know that. Technicians know that. It still doesn’t get done.

Coolant that is full of contaminants and boasting a pH at the acid end of the scale is a coolant that has done its job. If the coolant that came out of a system is so contaminated that you wouldn’t want to use it to wash a pump, why would you put it back into a system?

When this occurs the acidic nature of the depleted coolant can eat up a water pump. In addition, particulate matter such as rust scale and other contaminants is very abrasive and can wear out the pump seal rapidly.

Of course, fresh coolant mixture should always be used, and distilled water used to dilute the coolant to its 50/50 mixture. This doesn’t happen often enough and water in some areas can be extremely hard and this too can be a contributing factor in premature failures.

Another prime reason that pumps can fail early is overuse of sealants. When technicians are working on cooling system repairs involving mating surfaces or gaskets that they don’t trust to make a good seal, they will often resort to RTV sealant. These are fine in moderation, but if too much is used, it can work its way into the cooling system and find the water pump.

Externally, one of the high-ranking causes of failure is belt tension and shocks coming through the drive belt as a result of a worn or malfunctioning tensioner. This can cause premature bearing failure.

The fact is that on systems using serpentine belts and/or tensioners, by the time a water pump fails, it is a safe bet that the tensioner is due for replacement.

When you get right down to it, employing the basics of proper maintenance can all but guarantee that the replacement water pump will live a long and useful life.

Special thanks to Craig Gottfried, technical assistance supervisor, Master Parts Div., for his assistance.

Top Tips For Water Pump Repair

Always ensure that the cooling system is flushed and a fresh coolant mixture is used at any water pump replacement. Contaminants can dramatically shorten the life of a water pump.

Sealants, such as RTV, should be used carefully. Excess sealant can end up causing damage in the cooling system.

Check the belt, tensioner, and pulley. Each should be checked for condition and function, especially tensioners. Too much tension, or too much shock being transmitted to the pump pulley, can cause premature bearing failure.

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