Do Water-Pump Lubricants Really Work?

This article was originally published on Counterman.com

While some additives can be good for your cooling system, not all additives are. There are some additives that are just snake oil. A good example would be additives that claim “water pump lubrication” as a benefit.

What are Water Pump Lubrication Additives?

There are some additives solely dedicated to lubricating your water pump (or the entire cooling system). These additives usually contain a water-soluble oil formula that runs through the entire cooling system, including the water pump. Water pump lubricant manufacturers claim that their products not only lubricate the water pump seal, but they also prevent rust and corrosion.

Sounds like a great solution, doesn’t it? However, there’s one problem: modern water pumps are self-lubricating, so it’s pretty pointless to add water pump lubrication additives to your cooling system.

Modern Water Pumps Can’t Be Lubricated

Water pump design has changed over the years. A modern water pump has a permanently lubricated sealed bearing. There is a seal at the front (pulley side) of the bearing, and two seals at the rear (impeller side) of the bearing. If coolant seeps past the rearmost seal, it will then drain out of the weep hole that sits between the two rear seals. So it can’t actually lubricate the seal immediately at the rear of the bearing. And, it can never actually reach the bearing as long as both seals are in good shape. Coolant can only reach the bearing if both seals have completely failed. At that point the pump needs to be replaced.

Contrary to what water pump lubricant manufacturers would like you to believe, water pumps won’t fail as a result of rust and corrosion. Rather, it will fail from one of the following issues:

• Seal failure due to old age (or an early age if they were poor quality seals)
• Bearing failure due to old age (or a poor quality bearing assembly)
• Coolant contamination (due to head gasket failure)
• Coolant degradation (due to old age)
• Excessive drive belt tension

In a nutshell, any additives in the coolant will have no practical effect on the life of the water pump bearing.

Why are Water Pump Lubricants Still On the Market?

Many years ago, both water pumps and coolants were a lot different than they are today. Coolant lubricants served a legitimate purpose. And they still do, for people with older, collectable cars. But both pumps and coolant have greatly improved. Many OEM powertrain warranties will cover a water pump from 60,000 on up to 100,000 miles. And none of the OEMs recommend coolant additives, despite being on the hook for an expensive repair if the pump fails.

A Quality Water Pump Makes All the Difference

A cheaply built water pump with low quality seals and bearings just won’t last very long. You are doing your customers a favor if you recommend OE quality pumps with high quality seals and bearings. Not too many people enjoy replacing water pumps, so it’s important to provide the highest quality pump.