Timing Belt Tracking
#1
Timing Belt Tracking - Solved
I finally have the timing belt installed on my 1980 US, but the belt is tracking off the front of the tensioner roller as I rotate the engine by hand. Twice I have loosened the belt and reset the belt in the middle of the roller, but it continues to track off the front of the roller. The belt is staying relatively center on the cam pulleys. The first time I reset the belt, the pin on the tensioner had shifted out of line. Belt tracks further off the tensioner with each engine rotation.
I replaced the WP, pulleys, arm bushings, rebuilt the tensioner, but I did not replace the bolt at the roller/tensioner arm (pivot pin). The tensioner arm has a lot of play (it is able to rock, but does not move laterally).
What could be causing the belt to track off the tensioner? Should the arm be able to rock on the pivot pin? First trial, belt tracked to the back. Note the arm at the pivot.
Current setup, reset in center of tensioner. I have not tensioned the belt.
Current setup...arm looks offset at pivot.
I replaced the WP, pulleys, arm bushings, rebuilt the tensioner, but I did not replace the bolt at the roller/tensioner arm (pivot pin). The tensioner arm has a lot of play (it is able to rock, but does not move laterally).
What could be causing the belt to track off the tensioner? Should the arm be able to rock on the pivot pin? First trial, belt tracked to the back. Note the arm at the pivot.
Current setup, reset in center of tensioner. I have not tensioned the belt.
Current setup...arm looks offset at pivot.
Last edited by mkriete; 04-16-2017 at 11:13 PM. Reason: additional info
#3
usually it is a combination of a bent pivot bolt and the worn bushings,
also not fitting the snap ring to the tensioner roller ,
and having the wrong tensioner arm fitted,
or a waterpump .
I have seen different water pumps put the tensioner arm in different locations,
do you have a new Laso pump installed?
Posting pictures of what your doing will provide much more info to us
also not fitting the snap ring to the tensioner roller ,
and having the wrong tensioner arm fitted,
or a waterpump .
I have seen different water pumps put the tensioner arm in different locations,
do you have a new Laso pump installed?
Posting pictures of what your doing will provide much more info to us
#4
I edited the first post with pictures. You can see where the belt tracked to the back of the tensioner the first time. At this point, the tensioner pin had slipped out of place. I removed the pivot bolt and arm to reset the pin in the tensioner. The next couple trials the belt tracked to the front. I don't have pictures of these trials.
#5
you need another hands on experienced person that has done this before examine all of the parts you have,
something has not been properly assembled.
In the first picture the roller will hit the back of the damper.
something has not been properly assembled.
In the first picture the roller will hit the back of the damper.
Last edited by Mrmerlin; 04-02-2017 at 12:28 PM.
#6
Looking at it, I was thinking something Stan just posted: the problem is the installation of the tensioner roller, or the roller P/N itself. Is the tensioner arm seated? (looks like it) A third guess is that there's on thrust washer behind the crank gear. It's really odd to have the belt track that far off right after the crank as that's holding it firmly.
How does it look at the 1-4 cam?
How does it look at the 1-4 cam?
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#9
I must say that I am amazed at the wealth of knowledge on this forum . I researched more about the tensioner arm and pivot bolt and found that the early bolt are NLA. My bolt did not look original, so I pulled the bolt...again. It does not look like I have the original bolt or tensioner arm (see the pictures below). The tensioner arm appears to be from an 83-84, but the bushings are for an early bolt. Does this analysis look correct? Thanks again
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#10
In the 3 pics in your first post, it almost looks like there are no bushings in the arm on the shoulder bolt. Am I seeing things or do you need to double check your assembly? In the final two pics you show a measurement of the bore of the arm for the pivot (shoulder) bolt, and of the bolt itself, but the critical measurement is of the bore with the bushings in place.
#11
Here are pictures of the bushings. Is it normal to be stretched like this? Also note the wear pattern from the washer on the bolt vs the bushing position. The bolt seems really loose in the arm.
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#12
not normal. You have early bushings on a late pivot bolt. That's your issue. Need new bushings and might as well replace bolt
#13
Those bushes look like the early bushes 999 924 002 40.
You probably need 999 924 002 40.
You probably need 999 924 002 40.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
#14
#15
Thanks. No way I would have ever known where to look if it wasn't for all the help and knowledge on this forum.
Roger, please send me a new pivot bolt and bushings.
Scott, I still welcome your expertise.
Roger, please send me a new pivot bolt and bushings.
Scott, I still welcome your expertise.