At the heart of the cooling system is the water pump. It spins as does the engine in order to continuously circulate engine coolant through the automotive cooling system. Out from the engine, into the radiator, and then back again. So goes the water-cooled internal combustion engine. If the water pump fails in its task the cooling system will have the automotive equivalent of a heart attack. A few miles outside of Baker, California on a 107-degree day is usually where a water pump clutches its chest and quits. Steam pouring from under the hood and an engine clattering from detonation are sure signs of heart failure.

Sealed Impeller

The water pump takes its circulating power from the engine. Most operate through a belt and pulley and others via a gear or chain. The power spins a shaft on which there is an impeller. As the impeller spins it circulates coolant in much the same way a propeller on a boat works to tow drunken water skiers. The shaft and impeller spin on sealed bearing. Sealed, in order to prevent coolant from escaping the confines of the cooling system. This bearing is the part of a water pump that usually wears out first - followed by the shaft chewing up the pump housing.

Weeping Pump

A water pump that is about to give up the ghost will bleed or leak coolant. Coolant weaping from the underside of the water pump is the beginning of the end. The bearing inside the pump may also howl before it comes apart. Tell tale signs of a failing water pump are coolant leaks originating from the water pump, or if you're really out of luck, the water pump behind the timing cover of the engine. Coolant leaks can be tricky things to isolate. Check all the hoses and clamps and radiator itself before digging into the water pump and finding a heater hose was leaking coolant thanks to a broken 17-cent hose clamp.

Eat Your Vegetables

Since a water pump is either working or not replacement is a matter of necessity or preventive maintenance. If the water pump is leaking or puking coolant through a an unsealed bearing or cracked housing then it obviously needs to be replaced. Preventative maintenance is a good plan if the cooling system is half apart anyway, or if the water pump lives behind the timing cover or some more nefarious location. Water pumps that get their power from the timing belt or chain are often located inside the engine, and best replaced when servicing either component, or vice versa.


Five Servings

With any luck the water pump will be mounted to the engine in such a way that it can be easily removed and replaced. This is true of the good lot of water pumps. If leaking coolant is obvious but the location of the water pump is a source of great mystery, then the engineer that designed the cooling system has played a cruel joke on the DIY greasemonkey. Once again we cannot stress enough that the most important tool in the toolbox is a service manual. Search the message boards for digital copies if driving a Meapsy or a Citro n Ami. If the water pump is easy to find then it should be fairly easy to remove and replace. If not then some reading may be required. The following should supply a basic idea of water pump removal and replacement.


Stuff You'll Need:

· Vehicle Service Manual
· A Replacement Water Pump and Gasket
· Engine Coolant
· Distilled Water
· Hand Tools
· Catch Container
· Drip Pan
· Scraper
· Replacement Belt (optional)
· Anti-Sieze Compound
· Ramps or Jack and Jack Stands


Remove the radiator cap and drain the coolant. Look for the drain petcock on the bottom of the radiator. Remove the radiator hose or hoses. It may be easier to replace the water pump with the radiator removed. Now is also a good time to replace the radiator or have it recored it rot has set in. If the radiator remains be careful not to ding it or the AC condenser up with ham-fisted wrenching.


On v-belt equipped engines break loose, but do not remove, the water pump pulley bolts before releasing belt tension. The tension will prevent the pulley from spinning instead of the bolts. Drop v-belt tension at the alternator and remove belt from pulley. Remove the pulley bolts and the water pump pulley. Serpentine belts employ a spring-loaded tensioner. Throw a wrench on the tensioner to achieve belt slack.


Loosen and remove water pump bolts. Important! Take note of bolt length and mounting location. These bolts can extend into the engine and can cause problems reinstalled in the wrong location. Remove the water pump. Be prepared for more coolant with a drip pan under the engine. Engine coolant is poisonous, but dogs and cats can't read.


Use a scraper to free the engine side mounting surface of all old gasket material and sealant. This task will supply plenty of time to curse the previous owner who gave cousin Leo a six-pack to install the water pump using an entire tube of RTV silicone. Do not use silicone sealant unless the service manual calls for it. Sealing is what the gasket is for. Removal of all the old gasket material is the key to new gasket sealing.

Compare the old and new water pumps and bolts. Sometimes the mounting ears on replacement pumps are of different than stock, and require a trip to the hardware store for different length bolts. When installing bolts use a small amount of anti-seize compound on the threads to help prevent galling, stripped threads, and swearing.


Place a new gasket on the water pump. Gasket sealer works great for holding the gasket to the pump. Put a thin coat on the pump, and another on the gasket. After the sealant dries mount the gasket. No glue huffing! Install the pump. Tighten bolts to recommended torque. Reverse the take everything out of the engine bay to get to the water pump procedure. Don't forget to close the radiator drain petcock.


Either return original coolant to the cooling system or refill the radiator a 50-50 mix of new coolant and distilled water. Minerals in tap water can cause corrosion, which can kill water pumps. Fill radiator 3/4 or so full. Start engine. Turn on heater. Slowly top off radiator with engine running to burp any trapped air from the cooling system. Replace radiator cap. Watch for leaks.

Replace a Radiator or Heater Hose; Replace a Thermostat; And You Will Know Us by the Trail of Parts [Internal]