4 Mistakes Even the Pros Can Make When Installing a Water Pump

Water pumps are generally reliable, at least compared to the ‘good old days.’ On a modern engine, it’s not at all uncommon for a water pump to last longer than the vehicle.

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Still, despite their reliability, it’s often a good idea to replace a water pump during the course of normal maintenance. The thinking is that it’s cheaper – and safer – to replace a water pump than to let it fail, especially if removing and replacing a water pump can be done for only an incremental cost.

During the course of water pump replacement, it’s possible for even the most experienced tech to make a mistake that will lead to premature pump failure. Here are four common mistakes that even a pro can make installing a water pump.

1. Bad Seals

Faulty seals are the most common reason for failure. An improper seating, damaged seal, or misaligned gasket can mean the water pump is not operating efficiently or, worse, is under undue stress from misalignment. Improper installation will likely also cause immediate leakage from the mounting surface.

Many times, the installer will use the manufacturer recommended O-ring or seal, then “supplement” with a gasket set or sealing paste when it’s not called for. Re-using old seals or “making due” with the wrong seal is another common problem.

When a seal from a tube is recommended, properly applying and allowing for enough drying time are best practices. Failing to do so can result in seal problems. If excess sealant is applied to the gasket and it flows into the coolant system and the pump’s shaft seal, it can cause seal failure in a matter of miles.

2. Dry Rotation of the Pump

The “mechanical” seal within the water pump is created by the steady flow of fluid within the pump itself. When coolant flows through the water pump without air bubbles or breaks, this mechanical seal remains intact. The introduction of pauses or lapses in the coolant (usually air) can temporarily break and overheat that mechanical seal, which can then cause other problems.

For this reason, when refilling the cooling circuit after replacement of the pump, many shop manuals recommend the pump be hand-rotated until it’s full. This “charge” of the circuit can reduce the chance of a mechanical seal loss.

3. Improper Belt Components

The drive belt for the water pump can be either the timing belt/chain for the vehicle or a serpentine/accessory belt. If either is installed incorrectly or if other components driven by the belt seize or have rotational problems, this can affect water pump performance and eventually lead to failure. A misaligned belt that isn’t fully engaging the water pump’s pulley is another concern, as it can put undue pressure on the pulley and shaft.

4. Bad Coolant

The wrong coolant, which can happen, and bad coolant, which is more common, can cause issues for the water pump. Contaminated coolant or coolant with improper chemistry can cause seal failures, corrosion, and more. Abrasive particles and engine oils are the most common contaminants that wreak havoc in a water pump. During coolant flushes, completely draining and using the correct fluid as replacement are paramount.

The water pump wizards over at Tuff Stuff Performance field a ton of questions about things like pump sizes, flow rates, belt routing, and all sorts of other cooling-related issues.

They shared the questions customers most often ask them about water pumps. It’s a good read if you’re looking at replacing or upgrading your current mechanical water pump.

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Q: I installed a new water pump in my car but it’s still running hot. Why?

A: Engines that have been modified for more horsepower generally run hotter than stock engines. You might look into a pump with a greater flow rate than the stock pump, like Tuff Stuff’s Supercool water pumps. If combined with the proper thermostat and radiator, your engine’s overheating problem can be resolved.

Q: How do I know when I need a reverse-rotation water pump?

A: Typically, if you’re able to select a water pump by your vehicle or engine’s year/make/model, you can be sure that the water pump will be an exact replacement for your vehicle. If that’s the case, you shouldn’t have to worry about whether or not it’s reverse-flow.

If you’re building an engine or upgrading from a V-belt pulley to serpentine, you need to assess your situation further.

As a general rule, most serpentine systems require a reverse water pump.

You can determine this by seeing how the belt travels around the water pump pulley. If the back of the serpentine belt travels around the water pump pulley, you will need a reverse water pump.

If the inside of the belt travels on the water pump pulley, you will require a standard rotation water pump. Most pulley and bracket manufacturers can tell you what style of water pump you need for their system.

Q: What are the advantages of an aluminum water pump?

A: Some water pumps are available as aluminum rather than cast iron.

Aluminum pumps are much lighter than cast iron and can be polished to a high luster without rusting.

Q: How do you measure the height of a water pump?

A: “Hub height” is the industry term for measure a water pump’s height.

The hub height is a critical belt-alignment dimension determining where the water pump pulley belt groove(s) fall in relation to your crank, alternator, power steering pump and air conditioning pulley grooves.

The dimension from the mounting gasket surface to the outside face of the hub (where the pulley is bolted) is the hub height.

For example, it is especially helpful to know what the hub height dimension is to determine whether your Chevy water pump is a long- or short-style. A long or short water pump may be used on any Chevy V8 (Gen. I SB-Gen. II BB) engine as long as the correct pulleys are used and the belts are in alignment.

Never attempt to press or pull the hub to change its dimension. This may result in an unbalanced fan blade that can explode the pump and cause serious injury. Water pumps can be special-ordered with a specified hub height or shims can be purchased to adjust the pulley outward in small increments.

Contact us to discuss your requirements of Mechanical Water Pump For Cars. Our experienced sales team can help you identify the options that best suit your needs.