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Timing belt tension??

Discussion in 'Discussion Forum' started by Eastep, May 7, 2018.

  1. Eastep

    Eastep Dub-ing

    Location:
    PA
    I was wanting to paint my timing cover, and I noticed there seemed to be a lot of slack in the belt. Is this amount normal?
     
  2. Michael Hunter

    Michael Hunter True Classic

    Looks too loose for my comfort level...imo...mines not that loose
     
  3. mkmini

    mkmini True Classic

    Location:
    Latvia
    In manual it is written, that belt should be so tight, that could be twisted 90 degrees by thumb and “next” finger between cam and oil ?pump? pulleys.

    It worked for me, all 130km I drove it :D

    *it looks too loose
     
  4. myronx19

    myronx19 True Classic

    Location:
    Toronto, ON Canada
    What I do might not be right, but here's what I do (I should probably read the manual! lol...)

    I use the spring in the snail mount to pre-apply some tension on the belt, I use a pry bar to give some additional tension on the belt by moving the tensioner toward the front of the car. This additional tension is subjective, and variable - so not the best method.

    I now have a belt tension gauge, but I'm not sure it's the best thing for timing belts.

    How old is your belt? Check the nut that holds the tensioner bearing as well. How old is your bearing? Does it look OK? Are you due for a change anyway? Since you'll have the cover off, start the car and see if the belt flaps around a lot (while revving up the engine) or walks on the pulleys. If you have a stethoscope, have a listen to the tensioner bearing. Mine was making a racket, so I knew it was bad. I was lazy to change it, and drove another 5K kms before I changed it :)

    The belt is super inexpensive, and the bearing is also quite cheap - worthwhile insurance to change if it's due but I've extended that "due date" many times over... from being lazy, lol..
     
    Ernie likes this.
  5. Eastep

    Eastep Dub-ing

    Location:
    PA
    Thanks. I was surprised too, as I've driven several thousand miles since purchasing the car two or three years ago. It currently runs like a champ. The PO had the belt changed a year before I bought it. So probably only 10-15k miles on it.
     
    myronx19 likes this.
  6. dragonsgate

    dragonsgate True Classic

    Location:
    arkansas
    Some slack on the distributor side is normal.
    There should be no slack on the tension bearing side between the crank pulley and cam gear.
     
    myronx19 likes this.
  7. Eastep

    Eastep Dub-ing

    Location:
    PA
    I'll try to check the other side, this weekend.
     
  8. Waterbury

    Waterbury True Classic

    Location:
    Pennsylvania
    What is that filter connected to? The one right above your distributor cap?
     
  9. Rod Midkiff

    Rod Midkiff True Classic

    Location:
    Eugene, OR
    On my wifes car (doing a valve job on it their is a post with pictures elsewhere).

    I have changed the t-belt, and the bearing looked, sounded quiet. Then I spun it by hand and it had a LITTLE bit of roughness so change it I decided. pulled the bearing out and it fell apart! I was very suprised how bad it was, and was still quiet, with not much roughness to it.

    They are cheeper then a tow.
     
  10. aarpcard

    aarpcard True Classic

    Location:
    NJ
    Looks too loose to me. Assuming the tensioner is good, I suspect I know what happened - whoever installed the belt last didn't have the timing marks lined up perfectly and ended up with an extra tooth of slack on the side opposite of the tensioner. I've made that mistake before. The car will likely run (and maybe even run decently), but your timing will oscillate by a few degrees every rpm. Also, extra force will be applied to the tensioner and timing belt with each oscillation which increases the likelihood of skipping a tooth, and prematurely wears both components.

    If I were you, I'd be doing a timing belt job right now. Maybe it's just the tensioner that's failing, but even if the tensioner is the culprit, the belt should be replaced as well due to the extra forces from the oscillations it has seen.

    EDIT: I'm tired so I felt I should clarify as idk how coherent my post was. The belts on both my X's is/were nowhere near that loose. They had maybe a few millimeters of play with ~5lbs of force applied. The only time I've seen a belt that loose was when I did the job incorrectly on my MR2 and had to redo it due to the above described issues. The car ran (and ran smooth), but the slack resulted in the belt slapping against the timing cover.
     
    Last edited: May 8, 2018
  11. The best way I have found to properly tension the belt is to leave the tensioner retaining nut loose and turn the motor through at least two full revolutions. This properly seats the belt on the pulleys. With that done, turn the motor so the crank timing mark is 20 degrees or so past TDC. Then put a wrench on the cam pulley and turn slightly in reverse rotation. This transfers all of the slack from the aux shaft side to the tensioner side. While slowly turning the cam back toward TDC snug up the tensioner retaining nut. The tensioner's spring will properly tension the belt. Then recheck your timing marks and double check the belt tension.
     
    Dr.Jeff likes this.
  12. Mechanogeek

    Mechanogeek Daily Driver

    Location:
    Jacksonville, FL
    And not to be too smug, but when it comes to timing belts: "If there is a doubt, change it out."

    (You're welcome, feel free to use that quote any time).
     
    Last edited: May 9, 2018
    Dr.Jeff likes this.
  13. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    That "turn in reverse" trick is handy when first installing the belt as well. It's a lot easier to get the belt teeth into the right slots on the cam sprocket if you've let the sprocket turn slightly forward; and then use the wrench to turn the sprocket backwards into the exactly right position. The belt goes over the tensioner more easily when you have all the slack on the tensioner side, and you will know at once if you're off a tooth - the cam sprocket will turn a full tooth too far backwards.
     
    aarpcard likes this.
  14. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    That looks way too loose and as the others have said, if it were my car I'd be replacing it. Before you do, though, put a wrench on the cam sprocket and try turning it backwards (turn the motor to halfway between TDC and BDC first if you are cautious). If you can move it back exactly one tooth you'll know what was wrong the first time.
     
  15. Daniel Forest

    Daniel Forest True Classic

    Location:
    Montreal,Canada
    Just be cautious. I did that many time before without problems. But recently, turning the cam sprocket backward did just unscrew the cam bolt. Then, turning it forward the bolt sheared off. I had to remove the belt, drill and use a reverse drill bit to remove the remaining of the bolt and start again. I will NEVER turn the cam again using the cam bolt if everything is in place (ie resistance of the pistons moving up and dow). I will use the crank nut, even if it not as easily accessible.
     
  16. Eastep

    Eastep Dub-ing

    Location:
    PA
    Cra
    Crankcase breather.
     
    Waterbury likes this.
  17. Eastep

    Eastep Dub-ing

    Location:
    PA
    Thanks for the replies. I'll look into the belt this weekend. I think the tensioner side of the belt is pretty tight, and can only "deflect". The dizzy side, as you can see; is very sloppy. I'll update this thread, when I have more info.
     
  18. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    If you're putting enough torque on the cam sprocket for the resistance of the pistons to come into play that defeats the purpose of the exercise - we want the cam to move no farther than the belt will allow while the crank remains fixed, and that doesn't require much force at all. In particular, it's no more force than is needed to turn the am when the belt is completely off.
     
  19. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    Yep, that sounds like a tooth or so out. You'll likely find that you can rotate the cam backwards with not much force at all to transfer the slack to the tensioner side, and when you do you'll see that the cam is retarded a bit.

    (Much less likely possibilities would be having the wrong belt or tensioner bearing)
     
  20. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I would add that it is possible (but not highly likely) for the tensioning spring to become weak and loose some of its "tension". I haven't checked to see if there are new replacement springs available. But I'm not overly concerned about replacing mine. However I do give the tensioner piston/rod a little "nudge" from the other end to help assure it has fully moved forward (to the 'tensioned' position) before tightening the bolt. And on that note, make sure the tensioner rod moves freely. I've had them get corroded/dirty and stiff to move, which will effect it's ability to 'tension'.
     

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