COMMON WATER PUMP FAILURES & THEIR

CAUSES

1. LEAKING FROM THE WEEP HOLE: To understand leaking from a weep hole let's begin

with some common questions and answers.

What is the purpose of a weep hole?

The two holes you see in the water pump casting are called weep holes. The upper weep hole

acts as an air vent. It allows air to evacuate the casting system and prevents the build up of

humidity around the bearing. Also the vent allows atmospheric pressure into the pump and the

seal remains seated.

The lower weep hole exists to allow fluid to collect or drain out of the water pump to protect the

bearing integrity. In a horizontal centrifugal pump there is little space between the bearing and

the seal so fluid build-up could potentially threaten the bearing. Weep holes permit this coolant

to evacuate the system and protect the bearing. Weep holes also allow atmospheric pressure into

the pumps and help the seals to remain seated.

Does a drip from the weep hole mean seal or pump failure?

Perhaps. Seals will drip as the seal lap in but to understand a more prolonged or intermittent

drip you have to understand a seals design. Seals purposefully drip because capillary action draws fluid from the seal face. As the seal drips, it helps wash loose debris out and reduce the

heat load. Most drips evaporate or fall on the road and are not noticed.

Naturally, a more pronounced drip indicates a compromised seal and impending bearing failure.

What causes a seal to prematurely fail?

High Temperatures:

Mechanical seal have spring-loaded assemblies to keep the carbon seals intact and rubber parts

that may disintegrate if the engine runs hot or overheats. If a system overheats to the point of

boiling out and the system is permitted to run dry, the polished sealing faces can wear and

warp. A worn seal face allows fluids to escape and leak out the weep hole. Most pumps will leak

catastrophically shortly after a boil-over.

Electrolysis:

Electrolysis may cause filming and/or crystallization on the seal face and cause the seals to

permit fluid into the weep chamber. High mileage vehicle tend to have a greater incidence of

seal failure due to pH imbalance that compromises the seal face causing fluids to leak out the

weep hole.

Corrosive inhibitors are made up of silicates which plate metal surfaces. The degree of plating

that actually occurs varies but as it does, the silicate levels deteriorate over time and the coolant

becomes more corrosive. As the corrosion inhibitors deteriorate and the pH of the coolant drops

to 7 or below, the result is electrolysis and plating. For this reason most mechanics and

recommend a flush & fill at 24 months/30,000 miles. Unfortunately, few car owners flush and

fill and radiators and water pump seals become compromised.

Additive Gels:

It seems every few months a new chemical additive for the cooling system comes on the

market. Seal manufacturers find concentrations of gel from these additives and/or filming

deposits build on the seal face or they find carbon rip out on the ring. These all contribute to

premature seal failure.

Abrasive particles

If there are abrasive particles present in the cooling fluid can affect the wear resistance of the

seal. Sand is the most common.

2. BROKEN WATER PUMP HOUSINGS AND SHAFTS COMMONLY CAUSED BY:

Broken shafts are result of excessive vibration & unbalance and principally due to:

Bent, cracked, or broken fans

Fan not squarely mounted on the shafts

Cracked or bent pulleys due to improper handling or installation

Overtightened belts cause overload on the bearing and impose a powerful bending force

on the shaft causing it to deflect substantially from true center rotation resulting in

imbalance and early shaft fracture

What is covered by the warranty? Your warranty sheet is enclosed in the installation

materials. The warranty may also be found online.

http://www.flowkoolerwaterpumps.com/info/common_waterpump_failures.html