Water Pump 101

About Water Pumps
Nearly every automobile engine has a special pump (commonly referred to as a water pump), bolted o pump coolant through the motor, radiator and heater core. The pumps are almost always bolted to the front of the engine and driven by the main accessory drive belt. Water pumps circulate the coolant from the warm engine through the radiator, the water pump helps transfer energy in the form of heat (caused from combustion of fuel) from the engine to the air. In the process, the water pump draws cooler coolant from the radiator into the engine and cools the engine, preventing it from overheating. The main parts include the pump body which may be made of case iron or aluminum; a main shaft which is supported by bearings; an inpeller that actually moves the coolant and a mounting flange pressed onto the shaft to which the drive pulley and a fan mounts.

Pumps Fail
If you own your vehicle long enough, it's safe to say it's water pump will eventually fail. Unfortunately, there is no reliable way to determine when (or where) it will go out. Water pumps on modern vehicles can fail at around 50,000 miles, but may go as long as 150,000 miles. The best way to detect a problem before it becomes a catastrophe is to keep a watchful eye on the coolant level and keep your ears tuned to the engine sounds. The two most common types of water pump failures are leaky seals, or worn bearings. Leaky seals usually result in a small amount of coolant leaking out a difficult-to-see hole on the underside of the pump onto your driveway. A failing bearing generally produces a noticeable whirling noise that becomes increasing louder as failure progresses. Usually, a failing bearing eventually leads to coolant leaks. Before you suspect your water pump needs replacing be sure to do a proper diagnosis.

Replace ASAP
A failing water pump must be changed right away. A small leak can possibly remain a minor annoyance for as long as a week. Maybe. However, it could also turn into a torrid flow of coolant rushing out your vehicle's engine at any minute possibly leaving you stranded. Worse yet, an undetected low coolant level could result in serious damage to your engine.

Difficulty
Changing a water pump on most vehicles isn't terribly difficult, and downright easy on some vehicles, namely trucks and SUV's. It's a job that requires beginner to intermediate mechanical skills and common hand tools. The degree of difficulty often depends on the vehicle itself. For example, access to the water pump on some newer front-wheel-drive cars can be very limited. But even these can be changed, it just takes a bit more skill and persistence. Perhaps the worst part of all is the intimidation factor. At first glance, most water pumps appear covered with accessories and practically unreachable. But don't be intimidated. In most cases access is very easy after removing a few shields and accessories. In some cases you may need to remove the alternator and possibly other accessories. Refer to your vehicle's repair manual if you are uncertain. Generally, common hand tools are all that's required. Time required to replace a water pump can range from a half hour to a few hours depending on your vehicle, mechanical skill level and experience.

New Or Rebuilt Pump?
Replacement water pumps are available for nearly every vehicle at just about any automotive parts store. Unless your car is brand new (in which case it would be covered under warranty anyway), or an unusual application (such as a rare engine), there is little reason to buy a new water pump from the dealer (and pay substantially more). Water pumps can be purchased as either brand new or rebuilt units. Prices usually range between $15 - $60. Rebuilt water pumps are on the lower end of the price scale. Brand new pumps are all new, just as described. Rebuilt pumps (also called remanufactured) are reconditioned by special companies and feature new bearings, impellers and seals and whatever other parts need to be replaced. Since these are the main wear items, most mechanics and shops buy rebuilt pumps. Frankly, they're a better bargain in this authors opinion. Be sure to purchase one from a parts store that sells quality parts. When you buy a rebuilt pump you will need to return your old pump to the parts store so it can get rebuilt.

Follow along as we walk you through a typical water pump replacement in a pickup truck. Our vehicle is a common 1989 GMC truck with a 5.7L engine. The steps outlined in this example are roughly the same for most vehicles.

Step 1: Remove coolant