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Thread: Oil Pump Failure

  1. #1
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    Oil Pump Failure

    A couple of weeks ago my race weekend was cut short by something virtually unheard of: GT3 oil pump failure. A crack running along the base of one tooth of the impeller locked the unit up. We're not sure how the keyway could be stressed, and none of the very knowledgable Porsche guys that have seen this ever recall anything like it. Luckily only bearing damage, but note how the shaft was twisted off at the drive splines. Incredible.
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  2. #2
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    Wow, you musta been driving it hard!
    Life's too short to drive bad cars.

  3. #3
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    That's just it, I wasn't. Started up, warm idle showed 70 PSI, drove carefully out on a rainy track and only got 2/3rds of the way around.
    Never exceeded 5000rpm, shifted to 4th and everything went quiet... Telemetry showed nothing up to the drop to zero.
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  4. #4
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    so this is a new GT3 pump fitted on a 68 911S? Amazing how old engines can still accomodate new parts. I am sure it a sort of damage that Porsche guys would be interested to see.
    "I find the whole business of religion profoundly interesting, but it does mystify me that otherwise intelligent people take it seriously." Douglas Adams

  5. #5
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    Ouch. Hmm I'd check the history of the part and if it had been rebuilt at a time.
    That looks like a wrongly sized key causing a stress point.

    The end shearing my be a design decision - or just luck
    Let the cheaper part fail rather than spreading damage to expensive bits.
    Often see an undercut into a shaft to create these stress points.
    Sometimes ( the luck part ) they're there for oiling reasons.
    But better than it twisting a crank

    Will be interesting to hear what the Porsche racing community says about it.
    Bet everyone will pull their pumps and check for any signs of stress cracks
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  6. #6
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    These 2.0's at 115-135 hp/ltr are pretty highly stressed, so most builders utilize the GT oil pump. This one was built by the highly respected 901 Shop. Components are routinely magnafluxed and x-rayed between seasons... re-use of proven parts beats new most of the time. These pumps are so robust that thorough visual inspection during rebuild is typical. Reassembly is straight forward with the parts original to them, including gear keys... after all, there's no wear. The motor had only an hour on it since freshening, part of the deal when I bought the car and KS are standing behind their work. We're just relieved that it wasn't a catastrophic failure at high speed. So far the jury is still out, but yeah, others running this class might want to consider preventive inspection. Will be interesting if anyone finds a similar crack.
    Last edited by csl177; 02-21-2011 at 02:54 PM.
    Never own more cars than you can keep charged batteries in...

  7. #7
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    Final opinions on this suggest a freak occurance. Full inspection of all components included xrays... with 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 noted, it's not like these take much torque stress so the mystery remains. Regardless, close inspection during freshening will be practice from now on... oil starvation for even a few seconds = $$$.
    Never own more cars than you can keep charged batteries in...

  8. #8
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    wow its great

  9. #9
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    similar problem happened with me few days back..now I know how to get it fixed..

  10. #10
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    Quote Originally Posted by sporty car View Post
    similar problem happened with me few days back..now I know how to get it fixed..
    please elaborate, what car? when, how did you fix it?
    "I find the whole business of religion profoundly interesting, but it does mystify me that otherwise intelligent people take it seriously." Douglas Adams

  11. #11
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    My builder has just killed 2 of these back to back on his dyno.

  12. #12
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    Quote Originally Posted by lowyder993s View Post
    My builder has just killed 2 of these back to back on his dyno.
    Two GT3 pumps, back-to-back? Please... do provide details.
    Never own more cars than you can keep charged batteries in...

  13. #13
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    What we, in my profession, casually refer to as "Structurally Incoherent Metallurgy." The classical verbiage being: Progressive localized permanent change occurring in a material subject to conditions that produce fluctuating stresses and strains at some point or points and that may culminate in cracks or complete fracture after a sufficient number of fluctuations. I.E., Metal Fatigue.
    If no other, more plausible, explanation presents itself, one must needs consider M.F.
    Of course, one could do a proper, spot-on, stress and creep rupture test, ATS Series 2320 which includes a Finite Element Analysis (we do them daily in our labs), on the items in question. In fact, if Porsche is sufficiently curious about these failures, they should be clamoring to retrieve and verify (R & V).
    Last edited by novi; 07-31-2011 at 02:10 PM.

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