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308 Timing Belt Removal

Discussion in 'Technical Q&A' started by Sean F., Feb 5, 2004.

  1. Sean F.

    Sean F. F1 Rookie

    Feb 4, 2003
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    Sean F
    Someone help me out here.

    Which locking nut is he talking about. I see 4-nylock nuts holding on the tensioner assembly, and one large nylock nut holding the bearing itself. I don't see any nuts/bolts that look like they would adjust the position of the belt tension.

    http://www.cameragear.com/ec/timing.htm

    "- Each cam belt has a tensioner bearing that is attached to a tensioner bearing assembly. On those assemblies are self locking (nylock) nuts that lock the tensioner in place. These nuts need to be loosened, the tensioners retracted and the nuts retightened with the tensioners compressed. Be careful not to assert axial loads on the tensioners, as they tend to be quite fragile that way. I usually use a lever of some sort (pry bar) to compress the tensioner, but don't lever it by the roller bearing!"

    Maybe my question is how do I retract the tensioners?
     
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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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    There's a bit of a confusion in that description because the only "nuts" that you retighten for belt removal is/are the single large nut on each tensioner. What you need to do is:

    1. Loosen the large nut -- the roller bearing can then be moved relative to its aluminum base (the roller bearing is mounted on a spring loaded plunger mechanism that can be moved relative to the aluminum base when the large nut is loosened). Move/push the roller bearing to the position that gives the maximum belt slack, then retighten the large nut to hold the roller bearing in that position (relative to its aluminum base).

    2. Loosen the three small nuts holding the tensioner's aluminum base to the block. This allows you to "cock" the whole tensioner assembly giving more belt slack so that you can get the belt off without having to force it over the (fragile) lip on the cam sprockets -- these small nuts are not "retightened" to do the removal of the belt.
     
  4. Sean F.

    Sean F. F1 Rookie

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    Thanks. I was leaning that way but wanted to be sure.
     
  5. Sean F.

    Sean F. F1 Rookie

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    I was going to replace the bearings. Can I simply remove them once everything is loose?
     
  6. Gianluca

    Gianluca Formula Junior

    May 6, 2003
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    Mine were a little stuck. Actually one was very stuck. Other than that, once you remove the large nut, they free to come off.
     
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  8. 308GTS

    308GTS Formula 3

    Dec 27, 2001
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    A pic that might help.
     
  9. 308GTS

    308GTS Formula 3

    Dec 27, 2001
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    Clean and lube the tensioner/spring assemblies so they operate smoothly. Yes the bearing will come right off.
     
  10. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
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    I'm not sure from your post if you are just replacing the bearing, or doing the belt too. Note that you're not supposed to re-tension the timing belts, so if tensioner comes out, so should the belt!
     
  11. Sean F.

    Sean F. F1 Rookie

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    I'm doing the belt too.

    Thanks 308GTS. That picture makes thing much more clear. I've found a lot of those self locking type of bolts during this service. I've never seen many of those used on US cars.

    Any recommendations on the cam pulleys? I don't see a way to lock the cams so I can wrench on those bolts holding on the cam pulleys w/o some special tool. I've got new seals and I'd like to put them on as well (although, the existing ones did not leak at all).
     
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  13. Verell

    Verell F1 Veteran
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    May 5, 2001
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    BEFORE loostening the tensioners I use an air impact wrench to break the pulley bolts loose. I've got a 3/8" butterfly that does the job, but had to use a 1/2" wrench the 1st time.
    Put the car into 5th gear & lock the parking brake to ensure the engine can't turn.

    On a 2V car, you can get a thin wrench between the cam seals & the back of the pulley. There is a hex machined into the cams in that area.
    (Why oh why can't you find metric 'tappit' wrenches?)

    BTW, if you're only changeing the belts, you shouldn't need to remove the pulleys (assuming they were properly aligned at the last service.

    If they aren't leaking, leave well enough alone. Seals in good condition will hold up thru several belt change intervals. Just think how PO'd you'll be if you replace them & they leak & get your nice new belts oily.
     
  14. 308GTS

    308GTS Formula 3

    Dec 27, 2001
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    I agree if the cam seals aren't leaking leave them alone. Many times they leak after installing new ones. I have 2 belt changes on a set of cam seals. I won't mess with them until they leak.
     
  15. Sean F.

    Sean F. F1 Rookie

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    OK, thanks for the tips guys. Now I've got a bunch of seals and o-rings I won't need. I feel like I should use them since they cost so damn much money.

    Another question, if I losen the nut on the tensioner bearing, won't the tension in the belt cause the bearing to move? I've read I have to use a screwdriver or somthing to push the bearing away from the belt. I guessing the spring in the assembly holds the bearing against the belt ensuring proper tension? So, that means I'll have to push against the spring and retighten the nut on the bearing to give myself enough slack in the belt to get it off, correct?
     
  16. Gianluca

    Gianluca Formula Junior

    May 6, 2003
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    The belt will not push the tensioner bearing once you loosen it (the bearing) but rather the opposite; the bearing will, possibly, compress the belt more.
    If you have a strong hand, you probably can push the bearing away and re-lock it to remove the belt. There is not a whole lot of spring tension on the bearing.
    As suggested, make sure that the tensioner assembly get lubricated etc.
     
  17. Sean F.

    Sean F. F1 Rookie

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    From my link above;

    " Reinstall, if necessary, the tensioner carriers with tensioner bearings. The tensioner should be retracted to the mostly compressed state. "

    So I should fully compress the tensioners after I put the belts on to get the proper tension in the belts. What's the point in the spring mechanism in the system if you simply lock the tensioner bearing in place similar to what you'd do with an accessory belt? I'm missing something obviously.
     
  18. Verell

    Verell F1 Veteran
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    Put them in a ziplock freezer bag & lable them carefully, you'll need them eventually & they won't go bad in storage. I've got a set in storage as well.

    Usually the belt has taken a set & is exerting very little tension on the bearing & loosening the nut will let the bearing's spring actually apply MORE tension to the belt This is why you don't retension it once it's setup & worn in. All re-tensioning does is over-tension the belt.

    BTW, the belt's fibers are kevlar which doesn't stretch, under over-tension they just break. It's also why you can't tell how close to failure a belt is just by examining it. A belt can look good & still have a lot of internal fibers broken(hanging by a thread so to speak). Of course, if the belt has one or teeth in rough shape, it's clearly bad & on the way to engine destruction.

    Yes. I've found a set of small plastic handled pry-bars to be extremely handy, both for this & for adjusting the alternator belt's tension.
    Something like these:

    http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00930475000&bidsite=CRAFT

    http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=1654

    http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00943278000&bidsite=CRAFT

    Don't know why I didn't buy them 20 years ago...

    BTW, it's worth searching the archives for a lot of tips on cam belt replacement. eg: Using binder clips to keep the belts on the pulleys while working with the tensioners backed off.
     
  19. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Sean -- "Reinstall" in that case just means "to initially get the belts on" (and you should leave the three small nuts loose too). After tightening the three small nuts, you release the large nut (so the spring mechanism tensions the belt), give the crankshaft a few spins in the proper direction, and then tighten the large nut (so in the end the spring is out of the picture).
     
  20. Sean F.

    Sean F. F1 Rookie

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    Ahh, now that makes more sense. Thanks tr91.

    Verrell, I did search the archives but it came back with like 150 pages of threads. I tried to look through a few titles that seemed to make the most sense but didn't find much. I figured it was easier to just ask here. Besides, the next guy will be able to search the 'new' board and find this and hopefully it will be helpful.

    Thanks everyone.
     
  21. Verell

    Verell F1 Veteran
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    Well I must quibble with your attitude,
    I and quite a few others spent hundreds of hours carefully writing up text on the old Fchat & have no intention, or the personal time, of trying to recreate it here.
     
  22. Sean F.

    Sean F. F1 Rookie

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    Yet you keep replying ;)

    I really did search the archives, but like I said, their were 150-pages of links to individual topics (not 150-pages of posts, but links to topics) on the timing belts. And that was just the technical Q&A archives!

    Thanks for the help though.

    I'm going to take a bunch of pictures as I do this and maybe I'll find time write something up for Rob to put in the parts and service section.
     
  23. 308GTS

    308GTS Formula 3

    Dec 27, 2001
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    I use the search but lots of threads I remember never show up. Depending on the topic I think it is good to have a new thread from time to time as new information can be brought to the table. Look how many times we discussed the 308 fuse block and then another post where someone made an entire new fuse block. I am glad that thread came up. One of my cams will always move just a little. It is normally the exhaust cam on cylinders 1-4. Just make sure that you have it set exactly to where it should be.
    This will probably a pontential ? after you get your new belts on. I rotate my engine twice just to be safe. WSM says once, many pros do it twice. Also if you feel your belt halfway through your revolution and the belt seems slightly loose, or looser than it was before, it is normal within reason. The first time I felt this I got very worried. I checked my markings, cam timing, etc. for hours and I will still get that slight tension difference. Anyway just thought I would point this out.
     
  24. peajay

    peajay Formula Junior

    Apr 17, 2002
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    Good comment about the belts seeming to have variable tension, I found the same thing and also checked and double checked and triple checked. There is variation in the tension depending on what part of the rotation you stop at, you may find one belt tighter than the other for instance . It is probably due to the loading of the belt during a valve opening. But I agree it is quite normal.
     
  25. Dale

    Dale F1 Veteran

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  26. Verell

    Verell F1 Veteran
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    Yes, it's normal. The varying tension is due to lifting valves. It's more noticeable in a 2V engine than a 4V. This effect is implied by Ric's write-up, or else the FSM. One or the other tells where in this cycle to tighten the tensioner down.
     
  27. Sean F.

    Sean F. F1 Rookie

    Feb 4, 2003
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    you are correct Verell. Ric's write up mentions the tensioning proceedure, and turning it over twice, checking the index marks, losen and re-tighten the tensioner, turn over twice to check everything is correct.

    He also notes to be sure the tensioner is locked down or it will unduce harmonic's into the belt and prematurely break it.

    Thanks for all the input guys.

    I will not be able to losen the cam pulley's as my cams do not have any flat surface on them to hold them with an adjustable wrench. They're round all the way to the pulley.

    Since the seals do not leak, I'm going to leave them alone this time.
     
  28. zsnnf

    zsnnf Formula 3

    Sep 11, 2003
    1,877

    Other than broken teeth or being oil soaked, Is there any way to really tell if cam belts are about to break?? I can see tooth "shadows" on the back side (flat) of the belt. All the lettering is also worn off. Can these be considered warning signs of failure?

    It has been 5 1/2 years and 15,000 mile since they have been replaced, so I know they are due according to factory specs.

    TIA,
    Rick
     

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