Knowledge Building: Water Pump Failures and Coolant

After rebuilding an engine, you wouldn’t think of pouring back in the same motor oil, but when it comes to water pump failure and coolant, sometimes that is exactly what happens.

Naturally, even the most lunk-headed technician can see that this may not be an ideal situation, but few may understand just how ill-advised it is.

Starting at square one, it is important to understand that in a cooling system, there tends to be more than just coolant. There are a variety of contaminants circulating–from scale and rust to metal and silicate particles from the coolant itself–and the concentration of these rises over time, until at some point they start to seriously affect the ability of the engine cooling system to cool efficiently.

According to a survey conducted in the U.S., the condition of the cooling systems on cars is less than ideal.

The survey found that the cooling systems of seven out of 10 vehicles contained rust and scale; that more than 60% of water pump failures can be attributed to seal failure; and more than 50% of engine failures can be attributed to cooling system failure.

Additionally, a thin coating of deposits on a one-inch-thick portion of cast iron is equivalent to 3-1/2 inches of cast iron, reducing heat dissipation by 40%.

Proper cooling is, of course, extremely dependent on proper circulation of the coolant.

That is, of course, the job of the water pump. Most water pumps are perhaps not as robust as their predecessors; but rather than lightness of construction, it is the environment they live in which pushes them to the breaking point.

According to information from water pump supplier Master Parts, the condition of the coolant is critical to the function and longevity of even new pumps.

“When you lose a pump, the worst thing that can happen is having the technician take the old pump off, put the new one on, and dump in the old coolant,” says Craig Gottfried, technical assistance supervisor, Master Parts. “If it was a seal that did in the first pump, the coolant is probably in the same condition as the pump seals. If it’s nasty enough, it can go in a day or two.”

Note that he doesn’t say a year or two, or a month or two, but a day or two. Few if any technicians would blame old coolant for the failure of a water pump shortly after installation. More likely, they’ll point the finger at you or the supplier and, more than likely, you’ll begrudgingly take the blame.

Gottfried explains the reasons a new pump can fail so rapidly.

“Everything is going to be sucked into the seal because it is the lowest pressure part of the system and the hottest part, too.”

The situation isn’t necessarily helped by the expanding coolant options available on the market. While automakers and coolant manufacturers endeavour to colour-code their coolants so as to avoid confusion, for the car owner without even basic knowledge, the colour of coolant may be only a point of curiosity; maybe not even that. In a sense this is good, because it is not the sole distinction consumers should be looking at.

Coolants currently on the market include the standard life coolant, extended life coolant, Dex-Cool formulations, and G-05, which is a new one from Ford and Chrysler. There are also Supplemental Coolant Additives (SCAs)–common in the heavy duty market–but these are not a factor in the standard passenger vehicle market. In conventional coolants, the addition of silicates provides this protection. An antifreeze designed strictly for automotive use is high in silicate, while a strictly heavy-duty antifreeze contains low silicate.

While it is critical to ensure that the proper type of coolant is used in a given vehicle, perhaps more important is its condition, as mentioned, and its quality.

“Contamination usually damages the seal,” says Bob Rose, national sales manager, Fenwick Automotive Products. “Flushing is critical and, of course, there is the whole issue of cheaper coolants.” Quality coolants have additive packages to withstand the heat and contamination potential over the long term, says Rose, but this isn’t always the case when you work down through the price matrix.

“The economy brand coolants don’t have the formulation. If you see the water pump inside, you see how they can chew up the impellers. You see it in the deterioration of the water pump.”

Rose says that unlike severe contamination this only manifests itself over a year or two, but that is still well short of the expected life of a water pump.

“It’s the old story, the hunt for economy,” says Rose. “Can it really make a difference? If they were to see the damage that can be done, especially to aluminum, they’d never believe it.”

Flushing Prolongs Pump Life

There are several schools of thought regarding flushing, but almost everyone will tell you that it is necessary.

Some companies are advocates of chemical flushes, which have been accused of causing problems when residue is left in the system.

Some systems clean the system with high pressure, high flow water-chemical solutions.

Without comment on either of these methods, one gentle but effective strategy is to use a gentle flow of tap water, which ensures that all contaminated coolant is removed from the system, but leaves hard scale and any remaining casting sand where it is. While it is important to clean the system, it might be better not to dislodge these, which could cause more damage to the new pump if they end up circulating through the system.

In any case, flushing is a must. The consequence of having old contamination come into contact with a new pump is either rapid degradation of the pump seal, resulting in total failure in a matter of days or weeks, or slow deterioration over time to the seal and impeller. Maybe you should ask those of your service providers who are reluctant to flush which type of failure–fast or slow–they would prefer.