The water pump, while fairly simple in design, is an integral vehicle component that keeps the engine from the brink of meltdown. This month, we answer some of your questions on water pumps.

Question: How do I know if a water pump is going bad?

Answer: One way to spot a water pump with bad shaft bearings is to check pulley or fan play with the engine off.  The pulley or fan should not wobble or show any visible play when it is tugged on by hand.

QUESTION: Does a failed water pump always leak?

ANSWER:  Sometimes a water pump will fail internally. The pump may not be leaking, but the engine is overheating. If a cooling system pressure test shows the system is holding pressure (no internal leaks), and the problem is not a bad thermostat, a slipping fan clutch, or dead electric cooling fan, the water pump may not be pumping enough coolant. Some late-model water pumps have plastic impellers that are designed to reduce drag and noise. But over time, the fins on the plastic impeller can wear down, reducing the pump’s ability to circulate coolant through the engine. If the coolant
contains any rust or sediment, it will accelerate the wear process.  The same thing can happen to the blades on a metal impeller.

Question: What are the different types of water pumps out there?

Answer: Most water pumps are belt driven, but on some engines, the pump is driven by the timing belt. On most engines, the pump pulls coolant in through the lower radiator hose and routes it into the block and heads. On “reverse flow” systems, the pump routes the coolant into the head(s) first, and then to the block.
 
Question: We noticed a little bit of coolant had dripped from a water pump on a 1998 Chevy engine. I’ve heard that might be normal. Should the pump be replaced?

Answer: Because of the continuous load on the water pump, the seal and shaft bearings eventually wear out. The first sign of trouble may be coolant leaking from the pump shaft weep hole. More than a few drops of coolant coming out of this little vent means the seal is worn and the pump is failing. Other symptoms may include bearing noise (rumbling, chirping or growling), loss of coolant (through the leaky shaft seal), overheating (from coolant loss or separation of the impeller from its shaft), or fan wobble (if the engine has a mechanical fan mounted on the water pump shaft).

Question: Our instructor said there’s more to servicing a water pump than installing a replacement. What else do I need to do?

Answer: When a water pump is replaced, the cooling system should be drained, flushed and refilled with a fresh mixture of antifreeze and water to restore corrosion protection. Belts and hoses should all be carefully inspected, and replaced if any are found to be in less than perfect condition. Hoses that are brittle, aged, cracked, bulging or chaffed must be replaced. New clamps are also recommended. Belts that are frayed, cracked or glazed should also be replaced. If the engine has overheated, you should recommend a new thermostat, too.