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Crank pulley failed, snapped AC belt

Discussion in '456/550/575' started by stevepaa, Nov 2, 2020.

  1. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    The ac belt was getting slack in tension and the manual said I could retighten once. I did and the belt broke within 10 minutes of driving and caused some other damage.
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  3. Qavion

    Qavion F1 Veteran
    Silver Subscribed

    Feb 20, 2015
    5,183
    Sydney
    Full Name:
    Ian Riddell
    I can hear Taz saying "I told you so" :p

    Having said that, 3 years does sound a little premature. Now that the belt is off. How do the bearings feel? Any slop?
     
  4. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    8,686
    New England/FL
    3 years was created by Gates for marketing. :)
     
  5. AVIMAX

    AVIMAX Formula Junior

    Aug 5, 2014
    550
    Toronto
    Full Name:
    Ryan
    Something is not right in that photo. The crank pulley looks like it is not positioned properly on the crank, it looks too far forward. I see the belt for the PS and water pump is still on, but the idler for the AC belt is lined up behind the flange of the crank pulley. The front of the crank pulley should be flush with the plastic cover, it is not in this photo.
     
  6. AVIMAX

    AVIMAX Formula Junior

    Aug 5, 2014
    550
    Toronto
    Full Name:
    Ryan
    Hers a photo (not my car). You can see the belt for the PS in your photo is not in the right grooves. It should be forward on the crank pulley, your is on the back grooves.

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  8. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    #6 stevepaa, Nov 2, 2020
    Last edited: Nov 2, 2020
  9. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
  10. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    There was some oil on the crank bolt washer and the mating surface in the HB. Is that normal?
     
  11. AVIMAX

    AVIMAX Formula Junior

    Aug 5, 2014
    550
    Toronto
    Full Name:
    Ryan
    That explains what I was seeing in your first photo.
     
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  13. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    The tension pulleys are shot. No affect on unit pulleys.

    The guy that did my XK8 HB has done Ferrari 550 before and can do mine. I just need to check if there was a rotation in movement to align timing marks with crank slot,
     
  14. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    #11 stevepaa, Nov 4, 2020
    Last edited: Nov 4, 2020
    So I took of timing belt covers, and checked the belts. Timing is still dead on with the marks I put on 3 years ago. But the belts look like they were impacted by the shredded ac belt. The belt wound itself around HB shaft and pushed the pulley section forward and then the shredded belt rubbed against timing belts.
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    Then the edge of the pulley section contacted the two plastic idler pulleys and damaged them
    I think I will replace the timing belts, plastic pulleys, outside belts and have HB repaired.
    I set my engine to TDC and with the crankshaft locked I was able to rotate the pulley section to correct orientation for TDC.

    All of this happened just as I left the house and had driven 50 yards and I heard the snap and then could smell EPDM and I turned around and went back home.
    Thinking back, I think I had about 2 hours of driving around town after I had retensioned the belt. I am glad it broke so close to home.
     
  15. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    After further review, my assessment is the vibration damper pulley failed and started to move forward, snapped the ac belt and then impacted on the idler pulleys. The re-tensioning of the ac belt was not the cause.
    Although the belt wound around the base of the damper, it was not the cause of the outer section separating from the inner.

    Damper Doctor in Redding, CA cleaned up parts, and returned to me. I am having parts cadmium plated in Sacramento, CA and will come back just before Christmas and I will return to Damper Doctor to assemble with new rubber.
    Hopefully I will have the car running again in January
     
  16. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    20,344
    socal
    Wow amazing ac belt could have taken out timing belt! Note to self screw John's 3 year Gates marketing BS. Those belts are so cheap they are going to get routinely replaced on my 550.
     
  17. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    33,580
    Clarksville, Tennessee
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    Terry H Phillips
    FBB- Mine got replaced at 2 or 3 year intervals to match up with the 5 year cambelt service.
     
  18. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    Qavion likes this.
  19. ferraridriver

    ferraridriver F1 Rookie
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    Aug 8, 2002
    4,085
    Bay Area Calif.
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    Dave
    Hi Steve, who are you using for cad plating?
     
  20. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
  21. ferraridriver

    ferraridriver F1 Rookie
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  22. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    so I did lock and swap, turned crank a few times and everything lines up like when I degreed the cams last time. Sometimes the hardest thing to is to get the correct tension on the belts. Strum belt, get a reading, adjust, turn crank 1 turn, repeat as long as necessary.
     
  23. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
  24. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    car back on road.
    ~ $700 to repair vibration damper
    ~ $500 for new pulleys, timing belts, aux belts

    I am glad I was 50 yards from home when it happened and not on freeway
    I would suggest owners inspect the orientation of the inner section of vibration damper to outer section periodically to see slippage before failure.
     
  25. stevepaa

    stevepaa Formula Junior

    Apr 5, 2006
    549
    san jose, ca
    Full Name:
    steve
    well it turns out that TDC mark on repaired pulley is not quite correct, I checked with a dial indicator for piston TDC, a couple mm less than it should be. I will relay that to repair shop.
     

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