Oil Pump Failure

[Bullethead]

Just curious if anyone has ever seen this type of failure before. This is a GT pump in a 2.0 racing motor. Note the crack following the inside shoulder of the impeller. When it siezed it also sheared the drive end, note twisted splines. Any ideas?

Thanks in advance.

[Flieger]

It broke at the stress concentration where the corner of the keyway is. Perhaps there was a manufacturing flaw there (crack). The gears are not supposed to be transmitting much torque, right? Something must have jammed a gear first.

[Steve@Rennsport]

Thats really very rare.

Oil pumps generally fail from "swallowing" a piece of hard foreign matter and normally the case cracks.

Although its largely academic at this juncture, I'd take it apart to carefully inspect the gear tooth faces for any evidence of FOD as well as inspect the machined keyway to see if a stress raiser originated at that corner.

[ErVikingo]

Bullethead, Never seen that. Let us know what you find out.

[Bullethead]

There is no evidence of foreign material, all faces are clean and unmarked. The key had not been reset as the last check of the pump was simply opening the case and washing before reassembly. From other correspondance the concensus of some very experienced racing guys is they've seen this exact failure just twice before; once when a car was just being backed off the trailer. Shaft sheared off exactly like this. So, just freak metallurgical failure or something else? As Flieger notes, it's not like these take much torque stress so the mystery remains. Regardless, close inspection during freshening is good practice, oil starvation for even a few seconds = $$$.