Oil Pump Failure Analysis

A. Oil pump failure caused by improper installation

The pictures show the surface area where the pump interfaces with the block. Note the buildup of lock tight in these locations indicating presents of a gap.

 

The following four pictures show the height of the hardened material from the mating area of the pump in the two locations show above. Note: the thickness differences.

 

The final picture shows the broken area of the pump. No inclusions were found and no indication of overheat.

 

The break area of the housing showed no inclusions or flaws. Backlash was not an issue as there is no indication of overheat. The most likely cause of failure is a bending break of the pump housing occurring when the retaining bolts side loaded the housing causing it to crack. This in turn allowed the driven gear shaft to come loose and bind and break the crankshaft gear.

 

The inner surface of the housing shows where the foreign material channeled the pump housing.

 

C. Pump failure due to improper installation procedures.
The pictures show an end view of the broken shaft and a side view of the shaft. Note angle of break.

 

This shows the shaft bushing has failed in the pump housing with the internal part of the shaft stuck in it. The red arrow is pointing at the failed bushing.

 

 

The bushing failed from insufficient lubrication caused by excessive side loading. A shaft that breaks at or near a 45 degree angle indicates it has been under excessive torsional stress, a twisting break. The fact the bushing failed from side loading, one would expect a clean shaft break. However, when the shaft seized in the bushing the force of the engine twisted the shaft and caused the break to be torsional. The root cause of the pump failure was determined to be the pump was not shimmed properly and the gears did not have sufficient backlash.

  • Posted on   11/17/15 at 04:12:36 PM   by Sara  | 
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