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So I'm dinking around this evening checking everything on my car. I've had it a month now, and it has 62,500 miles on it. (92 SL) I say to myself "I wonder if the timing belt has been changed?" So I pop off the top front timing cover (very easy, just two bolts and it comes off) and I was SHOCKED at what I saw! The actual BELT looked OK, but it had so much slop in it I could almost make it skip a tooth on the gear! I sat down right then and there and decided it was time to do it. I took everything apart and right before zipping off the crank bolt with my airgun, I rotated the engine to line up the timing marks...everything lined up which is good (the car has been running fine) but now the belt is TIGHT again!
WHAT GIVES? I've got it to the point where I can pop the old belt off (including taking off that damn motor mount, what a pain in the butt) but didn't have the new belt yet so I left it on. The only thing I can think of after looking at it is there is some sort of "hydraulic looking" tensioner device of some sort down near the crank. Can that go bad? Is mine the correct symptom of it going bad?'
I'm telling you, it was REALLY LOOSE and after turning the engine its tight! Also, please give any pointers if you have any for putting this back together. By the way...The waterpump is BRAND NEW!
Thanks in advance!
Randy
 

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Lovbyts
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I'm sure you will get a lot of this but when you get a new water pump on one of these cars
it only makes sense to get a new timing belt because they have to take the belt off anyway so it only cost the difference of the belt. Also it seems everyone replaces the hydraulic tensioner when having the belt done just for good measure. I don't understand why or how they go bad but that seem to be the problem most people have so I would guess you need a new one. I do know you will need a special tool for adjusting the tensioner but I am not sure what. I have not done it myself yet. good luck and I hope I helped a little. I
you do a search on the site for timing belts I'm sure you will come up with a lot of info.
Also this is one of the most informative sites I have found. Make sure you book mark it. http://www.geocities.com/SiliconValley/8443/Other_gto_manual.html



[This message has been edited by Paul H. (edited December 29, 1999).]
 

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Since you have it torn down I would replace the hydraulic tensioner- may be going bad. Check to make sure tensioner pulley is turned properly. Both holes in front of pulley should be almost level. If not pulley may need some more tigtening. Uses a special tool that has two prongs that go into holes and tool connects to torque wrench so you can turn(remember to loosen lock nuton pulley first). Recommend leave belt on when do. Use bull dog clips(heavy duty paper clips) on each of the four upper cams to hold belt in position on cams. Use a paint marker to mark position of belt to crank gear( that way when take off know position to put it back at- providing belt is currently corect).
Something I remembered- before messing with tensioner pulley need to push hydraulic cylinder back into assembly(use vice to push together and insert small pin to hold closed-
Place pin through case and cylinder rod- you will see the holes).
Sorry to ramble- just a couple of tips.
Hope this helps,
Steve
 
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Discussion Starter #4
Yes, there is a hydraulic tensioner, and yes, I would definitely replace it w/ the timing belt!!!!!
 

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The hydraulic tensioner is not a tensioner at all but a damper that has only a modest spring, but serious shock action!

When cocking it in a vise, do so very slowly in small steps to allow the hydraulic pressure to bleed off.

However, this may not be necessary. With perseverance, one can tighten the timing belt with removal of the harmonic balancer and distorting the bottom half of the plastic shroud so see what you can see and get your tools in there.

Then, you may want to remove the motor mount and all of the shroud and replace the belt if your not in a pinch.

For the question as to why is the belt quite tight sometimes and not so at others. I expect that the cam sprockets have stopped at a position when the valve spring/cam action is torking toward each other slowly slacking the belt between one of the sets of dual cams. The pulley tensioner side of the belt will slowly push the hydraulic damper to its home position. This may take several minutes and only when the engine stops in this conducive position.

If, when this happens you move the motor to another position, the slack can show up in other places until the damper slowly takes it up.

Someone may have adjusted the belt as if the damper was a spring tensioner, and it needs tightening.

Normally as you run the car, the damper slowly takes up slack due to thermo expansion of the belt and back side belt slap.

Its a shock absorber that normally rest all the way home. Tighten the belt to the point that the tension of the belt holds the damper in the home position. You can pull the cocking pin in and out at the correct tension.

The cocking of the damper helps you to assemble and tighten the belt without slowly tightening in increments allowing time for the damper to retract under the belt tension.

But, I think that in your case you will find that when the belt is tight that the damper is extended too much. Over-tighten the belt in small increments until the tension is such that over several minutes the damper rectracts and remains very close to home.


[This message has been edited by EP (edited December 29, 1999).]

[This message has been edited by EP (edited December 29, 1999).]
 
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