360 timing belt tensioners | FerrariChat

360 timing belt tensioners

Discussion in 'Technical Q&A' started by Jerad Millermon, Apr 13, 2021.

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  1. Jerad Millermon

    Oct 3, 2020
    13
    Full Name:
    Jerad M.
    Did a belt service and noticed that after running engine a few min, if I shut the car off sometimes the tensioner's almost collapse to 0 distance. If I restart the engine they pop back up to correct setting. Doesnt happen every time. If I turn off the motor and turn motor by hand the tensioners also go back to the correct setting. I didnt replace the tensioners as its a 2003 with only 8000 miles. If its doing this now, then I would have to assume it was doing it before. Is this normal?
     
  2. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,344
    The Cold North
    Full Name:
    Tom
    As per the manual, after rotating the engine 2 full revolutions, the tensioner pin should be easily slid into the tensioner pin holes and (I think) a consistent 3mm gap must remain between the tensioner bearing lever arm and the hydrostatic tensioner body.

    By the sounds of it..you are too tight.
     
  3. Bowes

    Bowes Rookie

    Feb 20, 2017
    18
    South africa
    Full Name:
    Richard
    I’m having a similar problem . Also it’s difficult to get all acceptance criteria such as gap 1.9mm to 2.3 mm plus pin sliding freely in and out plus correct frequency. My gap is way less than 1.9mm but the pin slides in and out . It seems though that the tensioner is too low . Did you change the tensioners ?


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  4. 360+Volt=Prius

    360+Volt=Prius Formula 3
    Silver Subscribed

    Sep 1, 2013
    1,736
    Western Mass
    Full Name:
    Raimondo
    I’m no pro or engineer. I have witnessed this and given the reason some thought.

    There was another thread on this issue.

    Lose timing belt.
    https://www.ferrarichat.com/forum/index.php?threads/Lose-timing-belt%2E.637531/

    Read eric355’s posts.

    In addition to the cam lobe theory, I suspect there may sometimes be a subtle reversal of rotation due to uncombusted compression stroke before a piston reaches tdc . Perhaps it may act with the cam lobe for an additive effect to slightly reverse rotation just a fraction of a rotation.

    If you spin the engine in reverse by hand when doing the timing belts, you will see similar tensioner compression which corrects immediately when engine spins forward.
    -ray


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  5. Jerad Millermon

    Oct 3, 2020
    13
    Full Name:
    Jerad M.
    I did not change tensioners but I changed everything else. Im the 3rd owner and it had the original belts. Infact the gap was almost 1/4" per side on original belts. As long as your not too tight it seems as you have some leeway. After new the new belts I checked mine again after 200 miles and everything is with in spec.

    Just to note make sure your belts are new. I had several places trying to sell me "NEW" belts which had a manufacturing date of anywhere from 2006 to 2009. Call it what you want but in my book that is not new. I had to special order but finally got a pair with a 2020 date.
     

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