Rick's Free Auto Repair Advice

Water pump leak symptoms

Water pump leak symptoms

Symptoms of a water pump leak

Do you have a water pump leak? Here’s what to look for:

• Coolant reservoir is low and is low again after refilling
• Engine is overheating even at highway speeds
• Puddles of coolant under vehicle

What parts fail in a water pump

• Front seal wears
• Bearings wear
• Impeller disintegrates
• Cavitation damages pump housing
cutaway view of water pump bearing and sealWhat causes water pump damage

Coolant neglect

The #1 cause of water pump leaks and failure is coolant neglect.

Engine coolant has multiple jobs; preventing freezing, lubricating the water pump and prevent corrosion.

The base chemical in coolant polyethylene glycol doesn’t wear out. But it can be damaged by overheating.

In addition, the anti-corrosion and lubricating additives in coolant do wear out over time. Once that happens, corrosion can eat away at the bearing surfaces, gasket surfaces, and the impeller. As corrosion accelerates, the rust particulates wear out the seal. The the water pump leaks, causing even more engine overheating.

Driving with a coolant leak causes pump failure

If you drive with a low coolant level, the water pump bearings can’t be cooled or lubricated properly and they wear. The wear causes the water pump shaft to wobble and damage the seal, cause the water pump to leak.

Air or restrictions in the cooling system causes cavitation

Cavitation eats away at the impeller and water pump housing, causing overheating, water pump failure and water pump leaks. For more information on cavitation and what it does to water pumps, see this post

Using the wrong coolant can cause pump leaks

Most carmakers stopped using traditional green coolant decades ago. The older green coolant used silicates to provide the corrosion protection. Silicates deposit a “passivating” coating on all cooling system parts. The passivating coating deposits quickly disables the electrolysis action that always occurs when you have two dissimilar metals connected by an electrolyte—in this case, the coolant.

But silicate coolant has a short life; just 2-years or 24,000 miles. As the silicate coating ages, it disintegrates and comes off the surfaces of the cooling system. At that point the gritty silicate scrubs away at the water pump bearings and carbon seals, cause a water pump leak.

Modern coolants use organic acid anti-corrosion technology to avoid pump leaks and wear

Organic acid technoloy (OAT) is used in most new engines. OAT last much longer than silicates but takes longer to passivate metal components. So some carmakers recommend a hybrid organic acid technology (HOAT) coolant that contains a low dose of either silicate or phosphate. The low dose silicate or phosphate works quickly to passivate while reducing the abrasiveness of the coolant.

What’s important for you to know is that when carmakers changed image of silicate coating on radiator hoseto OAT or HOAT, they also changed the composition of critical engine seals, like the seal inside the water pump and intake gaskets. So, if you replace OAT, HOAT, or low silicate coolant with the old green stuff, you risk early failure of your pump and other engine seals. Don’t do it!!

Stick with your car maker’s recommendations. Contrary to claims by coolant manufacturers, there is no such thing as a universal replacement coolant. See this article on universal coolants.

Toyota and Honda owners should buy their coolant directly from the dealer. GM’s Dex-Cool is available at most auto parts stores.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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