why pumps fail

THE COMMON REASONS FOR PUMP FAILURE

WATER PUMPS 1.indd 1 30/10/07 12:13:29 PM

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WHY WATER PUMPS FAIL

FOREWORDThis booklet was produced for the purpose of identifying why water pumps fail and can be used to compare a water

pump that has been returned due to failure.

Comparisons given in this booklet will help in determining the validity of a claim.

This publication also shows some of the other common reasons for water pump failure such as incorrect belt

tension, cavitation, dynamic imbalance and electrolysis.


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WHY WATER PUMPS FAILTHE COMMON REASONS FOR PUMP FAILURE

CONTENTSPAGE 1 FOREWORD

PAGE 4-5 IDENTIFYING THE CLAIM

PAGE 6 BROKEN OR CRACKED HOUSINGS

PAGE 7 ELECTROLYSIS

PAGE 8 CAVITATION

PAGE 9 EARLY SIGNS OF SEAL FAILURE

PAGE 10-11 FAILURE BY CORROSION

PAGE 12 SEAL FAILURE FROM CORROSION



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BROKEN / CRACKED HOUSING.REFER BROKEN HOUSING SECTION [Page 6]

BLACKEND SURFACE / LEAKING.REFER ELECTROLYSIS & CAVITATION SECTION [Page 7]

LEAKING THROUGH WEEP HOLE.REFER EARLY SIGN OF SEAL FAILURE SECTION [Page 9]

In most circumstances, the water pump is blamed, as it is the most obvious part that displays evidence of failure.

The images below display all signs that the water pump failed because of other problems within the cooling system.

IDENTIFYING THE CLAIM



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EVIDENCE OF RUST DISPLAYED.REFER FAILURE BY CORROSION SECTION [Page 10-11]

EVIDENCE OF CALCIUM DISPLAYED.REFER FAILURE BY CORROSION SECTION [Page 10-11]

EVIDENCE OF PITTING AND CAVITATION.REFER CAVITATION SECTION [Page 8]

The main reason given for a claim is LEAKING. The weep hole displays evidence that coolant / water has eroded through the seal. This reason alone indicates that some form of severe corrosion has occurred.

If a water pump has been returned for replacement / warranty, compare the water pump to the pictures below to ascertain why the water pump failed and then refer to the section listed for a detailed analysis.


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These photos show a fracture around the base of the pump housing webbing. Failures of this type can be caused by dynamic imbalance such as fitting an old fan clutch to a new water pump. In this case the fan clutch had not been fully tensioned to the mounting boss resulting in a major imbalance problem.

Fractures like this have also been associated with over tensioning of the drive belt, although in those cases the pump bearing will also have suffered

BROKEN ORCRACKEDHOUSINGS


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ELECTROLYSIS

All of the above photos show dark discolouration of the inner pump housing which is consistent with the burning nature of current tracking into the cooling system.

Seals removed from these pumps had hardened and fragmented badly resulting in serious coolant loss. Microscopic examination of the housing surface displayed fine pitting marks similar to those seen in radiator core failures.


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CAVITATIONAbove and below photos show serious damage from cavitation. Exploding pockets of air slowly etching away at the pump housing caused the large crater in the floor of the pump. The light blue coloured hole in the crater is sunlight shining through from outside.

The extent of cavitation here would indicate a

problem/s with coolant, system bleeding and/or

air ingress.


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EARLY SIGNS OF SEAL FAILURE

Apart from the rusty coolant stains from the bearing relief hole, look at the build up of grease behind the fan boss. In this case coolant is entering the bearing from leaking seals and is pushing the lubricating grease through the bearing and out past the bearing seal.

Black coolant stains from the relief hole indicate a serious electrolysis problem with this cooling system and as a result the seals have been badly a� ected.

Other causes include no coolant or incorrect ratio of coolant allowing contamination and erosion through the seal assembly. Brown coloured staining is most commonly seen in this area and is the obvious sign that the cooling system is contaminated with rust.



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Both photos show extensive corrosion to the inner pump housing. The photo on the right shows how corrosion has attacked the surface of the pump shaft and the seal retainer collar.

FAILURE BY CORROSION

Above. Shows a rusty coolant stain from the relief hole, and corrosive build up around both the radiator

and heater hose spigots.



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Corrosion in this case has caused breakage of the seal causing massive coolant loss. The dark appearance of the housing would suggest this

cooling system also had a severe electrolysis problem as well.



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SEAL FAILUREFROM CORROSION

These seals came from pumps that had been in service for less than 4 months. Corrosion has caused severe damage to the seals resulting in massive coolant loss and subsequent engine failure.

The photo above shows cracking of the ceramic seal which occurs when adding cold water to a hot engine (thermal shock). Observe the extent of corrosion damage to the seat under the ceramic seal.


US Motor Works, LLC 16401 Berwyn Road

Cerritos, CA 90701 USA www.usmotorworks.com [email protected]

(T) 562-404-0488 (F) 562-404-8770

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