Serpentine Belt somethings not right

**B92 8NW** · 9th June 2009, 06:00 PM

Originally Posted by dullbird

I cant help but read what you wrote and feel you have two separate issues going on.

power steering one and the tensioner the other..........this is just my logic and I'm sure some will correct me and hopefully explain it a bit better to me. but I fail to see how a pulley out of alignment at the bottom of all of them would make a tensioner bounce. as the pulley in front and behind the tensioner would be straight therefore surely running the belt under the tensioner straight.

If the pulley is out of alignment we can assume that its axis of rotation is no longer perfectly centred, in other words, it is slightly eccentric. Thus, as the pulley is rotating, there will be certain points where the radius of the pulley is greater or lesser at the point where it contacts the belt. What is observed is an oscillating movement of the tensioner.

The pulleys immediately next to the tensioner don't cancel this effect - the belt is a set length, we know its 1580mm, the only way we could obtain more belt "length" is move the tensioner against its spring pressure - this is what happens when an eccentrically rotating pulley passes through its larger radius.

**loanrangie** · 9th June 2009, 06:01 PM

Simple really, the steering went heavy and i noticed my serp belt was failing , i put a new belt on straight away the tensioner started bouncing but stopped as soon as the inner rib ripped off and ran as normal . The belt shredding in the first place is due to the ps pump pulley cutting a rib off because it is failing . Car was driving as normal but i noticed the steering was getting harder to turn but i thought it was just that the belt was old and falling apart, i only noticed the pump pulley after i ran it with the new belt and can see there is a gap of 10mm between the outer lip of the pulley and where the belt was sitting - ie pulley and shaft has moved out 10mm or more.

**dullbird** · 9th June 2009, 06:22 PM

Is there anyway of checking other than play (pulling backwards and forwards) whether the PS pump is out of alignment?

Especially if the belt when on looks like its running straight.

the reason I ask is I have previously had a belt lose the furthest rib before....but that was when the tensioner was kicked out and the inner nylon bush had failed (or at least thats what we thought it was so maybe it wasn't that.

how ever although this tensioner has a bit of a bounce my old kicked out tensioner doesn't!!!! and also when refitted no longer appeared to have the kick that we took it off for.

In saying that I can't refit the old one as the nylon bush on the inner circle has broken. and it now squeeks its arse off.

**Piddler** · 9th June 2009, 07:09 PM

This issue seems to have been going on for some time Lou I would be over it. If you are careful you can use a string line with a torch to check pulley alignment. It should be pretty straightforward to see where your issue is.

Up your way Phil (Disco White) is a fitter he would be able to sort it out.

Cheers

**dullbird** · 9th June 2009, 08:21 PM

Originally Posted by Piddler

This issue seems to have been going on for some time Lou I would be over it

. If you are careful you can use a string line with a torch to check pulley alignment. It should be pretty straightforward to see where your issue is.

Up your way Phil (Disco White) is a fitter he would be able to sort it out.

Cheers

Thats the strange thing since changing the last tensioner it never chewed the edge of the belt up again.....but as you may know the belt got shredded.......but it was only the top of the belt the re-enforced backing that came off and got shredded the actual belt was still on all the pulleys...

So has the issue always been there? if it has it has taken nearly 3 years to rear its ugly head.

heres a vid of my tensioner you can see it having a bounce is this bounce exceptable? I have had people say to me that a bit of bounce is ok but my other tensioner (old one) didn't bounce at all......in saying that I'm assuming that my old one was genuine as the other two were sourced through karcraft. The thing I noticed between them was the two I got from karcraft (different brands) were easy to pull back with a bar when changing the belt. the genuine one was not so I'm also assuming the genuine one has a much stronger spring inside.

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**B92 8NW** · 9th June 2009, 08:35 PM

All looks pretty normal really.

See if it stops bouncing when you raise it off idle. It is a 4-cyl diesel after all...

**dullbird** · 9th June 2009, 08:38 PM

no with a few revs on its still bounced a bit a little smoother but was still doing as above.

The weirdest thing that happened when changing the belt was ok the day we changed it put it on run it etc........all good didn't drive it.

The next day we went to drive it and on start up and tick over we got a strange noise!! the only way I can describe it is: If you imagine a peice of parcel tape that has stuck to it's self in places but is stuck to part of the car and is blowing in the air/breeze and tapping on something.

(sorry that is the best way to describe it) that noise is there until you drive about 5 mins up the road and then goes and you don't hear it again. we search high and low for something lose/rubbing any thing abnormal and found nothing could not pin point anything other than around the belt region but everything looks fine!!!

we wonder after searching whether there could possibly be something sticky on the belt.......we are going to leave it a couple of days to see if it goes away. as have driven it for two days without a problem and the noise disappearing (although like I said is there on start up)

**steveG** · 9th June 2009, 09:59 PM

If you think it might be something sticky on the belt then try spraying a bit of water on it. If you do it with a bit of control (like from a spray bottle or similar) then you can spray one side of the belt and then the other.
If the noise changes/disappears then you know that the noise is being generated by something on that side of the belt.

Something else that I found when trying to track down a chirp in my main belt, was that the tensioner was bouncing (probably a little more than yours), but the tensioner pulley was rock solid and didn't move at all from side to side when running.
After putting a 1mm thick washer at the 9 o'clock position behind the tensioner the noise disappeared, the bounce was almost completely gone, but I also noticed that the tensioner pulley was now running gently from side to side (sort of a smooth tracking wobble). Seems the tensioner must have been slightly out of alignment and loading the pulley hard in one direction. Once the sideload from the misalignment was gone the pulley was free to move within the normal play in the bearing.
Maybe not so likely with your tensioner being a new one, but have a look at how that pulley is tracking. If it seems really solid and you've identified with the water spray that the noise is being generated on the back of the belt then it might be worth trying the washer trick to see if it improves things.

Steve

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