# ABA timing belt slipping off cam gear sideways?



## atticus939 (Feb 11, 2007)

I replaced the tb (and tensioner etc) almost exactly a year ago on my wife's '95 Cabrio. The project went fine, and the car ran/runs great.
Just the other day i had reason to drive it and noticed an unusual rpm-indexed whine, so i wanted to take a look at it... on the theory that the last thing you messed with is probably the part you broke, i took off the timing cover. Of course, there are belt shavings everywhere and the belt is riding on the outer edge of the cam sprocket. Clearly this is not correct. It tracked right in the middle when i installed it, and also about a month later when i checked again. The tension appears to be about correct (i can just barely turn the belt 90deg on the long leg).
She says it's been making that noise for "a couple of months" (Arrrrghh!!) but she didn't think it might be important.
SO.. what's causing this? Thoughts that come to mind:
-- bent tensioner bolt (tension too tight? Seemed like a very hokey/in-exact way to set tension
-- crank sprocket/cam sprocket out of round? Seems like this would throw the belt right away.
-- ???????

The timing cover has belt-dust all over the inside of it, but no circular marks like it's been rubbing, and the lip on the tensioner seems to be what tracks the belt.
The Bentley manual calls this a "camshaft drive belt" and does not provide a spec for wear on the width of the belt, but mine is .694" or 17.63mm (or so)
There does not appear to be any fraying of the edge of the belt, though there's plenty of dust/frass around. (see the top of the tensioner bolt)

Thanks in advance (for reading this long post, too)


















_Modified by atticus939 at 4:44 PM 9-3-2008_


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## mk2allday (Apr 27, 2007)

mine is like that too right on the edge


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## WackyWabbitRacer (Apr 24, 2001)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

Timing belts tend to ride on the outer edge of the camshaft pulley.
I would recheck the timing belt tension. Proper tension is when you can finger twist the belt 90 degrees at a point halfway between the camshaft and intermediate pulleys.
I know this seems vague but that is the proper procedure.
Good luck, WWR.


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## atticus939 (Feb 11, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (WackyWabbitRacer)*

Thanks for the response...
I did check the tension, it seems exactly right, by that method (90deg at the longest leg, by finger)
When i installed it (and the old one too), it rode more or less right in the middle.
I wouldn't be concerned about it riding on the edge, except that it makes that noise, which since i found a bunch of dust/fluff under the cover, i'm pretty sure is the belt rubbing on something.
It's like a "zzzziiiiiiiiinggggg" whining/whirring noise. I couldn't tell for sure what the belt is hitting though, and it's certainly inside the lip of the tensioner pulley.
Anyhow, thanks again for the response!


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## 4ePikanini (Aug 29, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

remove the cam belt covers and start her up
If she still whings then you got something to stress about.
If she goes quiet, line the outer and inner edge of the belt with white or silver paint or something, put the covers back on carefully not to rub.
Then run the car, remove covers and check where the paint has been dropped.
Let us know and post a pic of the bad part ! http://****************.com/smile/emthup.gif


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## Fat Rabbit (Nov 18, 2001)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

IIRC last time I experienced something similar years ago it turned out to be a bad motor mount that somehow was causing the timing belt to creep off. Replacing the motor mount and mount bracket fixed the problem in that case. Seeing the motor mount in the foreground of one of your pictures brought that back to mind.
I note that parts places talk of a 10mmX40mm stud kit 026 198 243 when upgrading to timing belt tensioner 026 109 243E -- did you do that?
Use a straightedge and maybe even a laser or dial indicator to check sprocket alignments. Replacing the belt and tensioner is probably in order. FR


_Modified by Fat Rabbit at 2:42 PM 9-4-2008_


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## the_elected (Aug 20, 2008)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

I've had several issues with the tensioner on my car. The first time I noticed it was when I bought a 268 duration cam. The tensioner was actually seized up and the bearing inside wouldn't move at all. So it actually turned out to be a blessing in disguise that I wanted to hop up my engine. ha Anyway since it was seized the belt would slide over the tension pulley and in time this would have ended in failure. The second time this happened my tensioner seized and it snapped the timing belt and bent every valve in the head. As best I could determine the aftermarket tensioner I bought from Advanced Auto Parts was "loose" fitting on the OEM bolt which resulted on it oscillating and eventual failure resulting in my timing belt giving up on life. After that I went with OEM parts I bought from the dealer. You could try taking the tension pulley off and looking at it. I would probably run the car with the timing cover off and see what I can see. Hope that helps. 


_Modified by the_elected at 8:11 PM 9-5-2008_


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## brandon400hp (Sep 6, 2008)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

looks good from the pic. as long as the belt is filly on the pulley, and not hanging off at all it should be fine. turn crank pulley over twice make sure marks and everything is golden, and start the car with the covers off. you will be fine without the acc. belts


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## jorge r (Apr 27, 2006)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

It seems to me the tensioner is out a little, out away from the engine. It seems like to me because the timing belt seems to start flush on the edge of the camshaft sproket and then there is a gap as it leaves the camshaft sproket. If this is true, it indicates that the belt tries to ride closer to the engine and the tensioner pulls it away a little. The belt should be in a plane as much as possible. 
I think it would not hurt anything, not right away. The uneven belt tension across the sproket teeth would eventualy wear the sprokets out of square, after a few belts and some time. Then there is the belt dust contamination. The situation would bug me and I'd double check to find what's going on.
edit: that dust on the tensioner stud nut, if it's under it too, then the dust probably comes from under it, only on top, then it would be falling on to it. Wipe it, and check again later.


_Modified by jorge r at 5:21 PM 9-6-2008_


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## atticus939 (Feb 11, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (jorge r)*

OK, i'm pretty sure i know what's going on here, but not exactly why.....
There have been some great suggestions and ideas here.
Here's what i did:
1) Inspected the entire belt path very carefully. Nothing is touching, and not the cover either... The cover has an undisturbed coating of belt-dust all over it. The motor mount rubber is indeed sagging, but i can not see how this could cause the belt to ride to the edge like this.
2) I put red disc-brake-quiet on the edge of the belt (first pic). I did that because it's soft, but when dried won't sling off the belt, and won't hurt anything in there. Also, i didn't have any white-out, which was my first choice.
3) I started the car, and ran it for a few seconds, up to 2000 rpm max. Pic 2 is what the goo looked like after that. Note that it's still on the edge of the belt, even though it's pretty thick, at least 1mm. 
4) When i inspected the rest of the belt path, it's obvious that the only place the belt is touching it's edge is on the tensioner. Note that in pic 2 the goop is cleaned off of the teeth, but not the top edge. The tensioner's edge is angled, but in the opposite direction that would clean the teeth but not the top edge. The belt is pushed way to the outside of the tensioner, and probably is being held on only by the tensioner. 
I surmise that the 'zing' noise is actually the tensioner being rung like a bell at certain RPMs. The real question here is why is the belt creeping to the outer edge of the tensioner's limit?
Possibly reasons:
-- Belt tensioner bolt. If the bolt is bent outwards (how? too much tension on belt?) then that angled/sloped surface would run the belt "downhill"
-- ??????? not a lot of other reasonable ideas?
Fat Rabbit's point about upgrading the tensioner stud is a good one.. i used OEM parts from the dealer and did NOT upgrade the tensioner to the new style (obviously.) Is that upgrade stud used with the old tensioner, or do i need to upgrade to the newer tensioner? Does this older block already have the provisions to upgrade the tensioner? Hmm....

























_Modified by atticus939 at 10:24 AM 9-7-2008_


_Modified by atticus939 at 10:27 AM 9-7-2008_


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## jorge r (Apr 27, 2006)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

I think the stud tensioner is more reliable than the thermal tensioner. Replacing the stud is to retrofit tensioners, or to have a fresh new more reliable stud than the previous one. I left the original in, twice already. 
There seems to be a wear of the timing belt teeth, there's a gap between the belt and sproket teeth. 
You can probably use the disc brake quiter quem. to quiet the tensioner. 
Last time I replaced my belt, a $62 NAPA kit in a box, I thought when tensioning the belt, which way to turn it? I went CCW because it would set a longer leg to the sproket above, as if it mattered. I see you went CW. 
I wonder if rotating the tensioner the other way, if it makes a difference in the tensioner pulley angle. The tensioner rests on the block. The middle part is like thick sheet metal plates, hollow with little flexing, and a bearing for the outer part.
There's no telling which way the belt will lean to unless a straight edge is used on the belt wheels once the belt is tensioned. I think a flat belt will go to the tighter high side of a wheel.
For me, I'm mostly observation and conversation, picking around for a way to correct the situation, it may take a new belt kit and keeping it under observation.


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## Fat Rabbit (Nov 18, 2001)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

The teeth on the belt (in the third picture - the one with the tensioner) look kinda strange to me - shiny with a line down the middle of each tooth. Almost like they have been pinched on the leading edge. 
BTW I still think the root cause is the motor mount. FR


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## atticus939 (Feb 11, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (Fat Rabbit)*

Yeah, the teeth do have a little valley down them, but that's how the belt came out of the box....

I don't disagree that it could be the MM doing it, but i just can't see how.... but weirder voodoo isn't hard to find, and the mount is squished so i'll probably replace it and see. If the belt magically goes back to the middle of the track, i'll be happy and not ask any dumb questions!
Ha!
I'll post back for sure, whether the belt breaks or the problem is resolved.
Seriously, i appreciate all the help folks.... And i hope this thread is useful to the next guy.
~a


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## wilburisthecoolest (Jan 13, 2008)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

I'd say rotate the tensioner the other way, so CCW, or 'down' instead of 'up' or clockwise.
But pretty strange issue if you ask me..


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## VDUBIN (Jun 28, 2001)

*Re: ABA timing belt slipping off cam gear sideways? (atticus939)*

here's my 2 cents... 
every time I have had a whining timing belt it's because it was too tight. you should be able to turn the tb 90' with a bit of effort, but not balerly able to turn 90'. I also have my tensioners turned down instead of up. with the tool on the tensioner turn it ccw to tighten. Works well and never lost a belt.
gl http://****************.com/smile/emthup.gif


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## atticus939 (Feb 11, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (brandon400hp)*

Well, just as an update.... two weeks later, car being driven daily, and it seems to be fine.
I thoroughly cleaned the cover and stuff in there, and as of today there isn't any new accumulation of dust/frass. The goop i put on the edge of the belt is mostly gone, but i can still see some traces of it, so it's not as though the belt is being worn away by anything.
So, chalk up another success for benign neglect?
Hm. I'm not super-comfortable with that.... 
Anyhow, the Bentley manual i have shows the tensioner being tightened in the direction that i did it (ie, pull towards the front of the car with the tool), which is clockwise if facing the pulley-end of the motor. Most of you-all tighten them the other direction, and honestly i have no idea which way it was originally.
Tonight i'll fabricate a new tool to fit the pins, so i don't have to use 90deg needle-nose pliers, which was a pain in the ass.
Can anyone tell me how many motor mounts there are on an ABA Cabrio? I only find three... two big (lower, front and rear) ones, plus the little one inside the TB. The other two look fine. The Bentley manual doesn't address replacing MM directly.

Anyhow, thanks again for all the help... and i'll keep posting back until i figure out what's causing this whine. Maybe a vid/audio of it would help, and you-all can tell me it's just normal and i'm a 'noid freak!
;-)
~scirocco
ps: oops.. ferget it about the MM... from under the car the "hidden" MM can be seen clearly on the left-rear. It looks fine too, though i don't have a lot to judge it against.


_Modified by atticus939 at 7:28 PM 9-21-2008_


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## sholford (May 21, 2007)

*Re: ABA timing belt slipping off cam gear sideways? (VDUBIN)*


_Quote, originally posted by *VDUBIN* »_here's my 2 cents... 
every time I have had a whining timing belt it's because it was too tight. you should be able to turn the tb 90' with a bit of effort, but not balerly able to turn 90'. I also have my tensioners turned down instead of up. with the tool on the tensioner turn it ccw to tighten. Works well and never lost a belt.
gl http://****************.com/smile/emthup.gif 

X2! If it sounds like a supercharger, it's too tight.


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## Rudabird (Nov 13, 2016)

*updates?*

I'm having this same exact problem. Its honestly uncanny how similar the troubleshooting pathways have been, as well as the results. Would love to hear if you ever cracked this one Atticus939, because I'm out of ideas.


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## Butcher (Jan 31, 2001)

This is a simple issue that can be resolved quickly. In a perfect world all the pulleys are in the same alignment. They are all parallel to each other. If one of them is slightly out of alignment, the belt will slide to that side. Done. No More Thinking. That IS the only reason.

So could the cam gear be off? Sure, but highly unlikely. Maybe some one could of shaved the head or block crooked.

Crankshaft gear? Could be, but again, do you really think the machinist screwed that up too? 

Intermediate shaft, maybe, the bearings can wear out and cause the shaft to be out of alignment. Lot of work to prove that. I would also suspect that the oil seal would have a big time oil leak, even with a new seal.

The only other pulley is the tensioner. That is where I would start. Is it worn? Is the bolt/stud straight? Is the surface of the tensioner flat? Any dirt under there?

If any pulley is bent, it will wobble and cause the belt to track every where.

The above thread has a lot of issues. Mostly because the belt sounds like it was way too tight and the bearing is shot.

One other thing, not related to pulleys is the belt. The belt must have the same tension throughout the entire surface. If one portion of the belt is longer [or stretches more] than the other side, it will not track straight. Good quality belts do not do this. You get what you pay for. Buy a good brand name belt. Do not over tighten it and replace the tensioner pulley.


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