cambelt movement/slippage 1.6k

[masha]

Has anyone experienced a cam belt that refuses to remain stationary on the front of the pulleys, but instead works its way to the back of the pulleys and rubs on the casing until it begins to wear's out. This was what I found recently, and fitting a new belt and running for a very short period of time today found the same movement even with a new belt and new belt tensioner fitted correctly?

 

The pulley's and water-pump are all true but there's a possibility the alternator pulley visually is wobbling about a bit and has worn where its been run when slightly loose at some point?

 

any suggestions below appreciated, alternatively email ms81@cant.ac.uk

 

thanks

Matthew

 

 

 

 

[gasha]

Boing

[Peter Carmichael]

Alternator is a different belt. How do you know you have fitted it correctly?? What else has changed?

[masha]

its all fitted correctly, in fact the reason for the urgent cambelt change was a quick visual inpection last week to find more than half the belt worn away against the back of the cam casing and auto-tensioner device. The tensioner was replaced, and both cam and alternator belts, and all adjusted and fitted correctly as per any other K-series cambelt job.

 

After finishing and turning the car over briefly found that new cambelt was upto its old tricks and you can already observe that the belt has shifted to the back of the pulleys and the spring/guide on the new auto tensioner is already showing signs of contact.

 

There must be a pulley out of alignment creating a 'deurailler gear' effect causing the belt to move, but cam pulleys look fine, water pump pulley looks fine, auto-tensioner looks fine. So that just leaves the crank pulley and the alternator pulley on the front of it that might be causing it? Not sure where to go from here: might try Caterham Techinical or Minister to see if its a problem they've encountered before.

 

Any ideas of what to do next greatly appreciated.

 

Matt

[Peter Carmichael]

Has the head been skimmed?

[oilyhands]

Its unlikely to be the crank pulley it's too far away, Peter might be on the right track, if the head has been skimmed at an angle front to rear then the pulleys will be running in slightly the wrong plane and will pull the belt off the edge of the pulley, alternatively one of the pulleys may be faulty, I have a few spare pullies laying around here that you are welcome to try.

 

Oily

[masha]

Thanks Oily/Peter - you might be onto something, I'll try to find out about the history of the head, we've only had the car a couple of weeks so not sure, but will ask the previous owner. I'll give you a should if I need to try some pulleys to elimate that, thanks. I may also try the alternator pulley as (probably not related) but that has been run loose at some point and distroyed itsself a bit at the rear, don't know if anyone has one of those too?

 

thanks again

Matt

[F355GTS]

Matt

 

I assume it's Gareth's car, so here's the history I know if it helps

 

The Crank Pulley came loose at Imola this year but was refitted and appeared/ worked fine, that's what probably damaged the Alternator Pulley.

 

Is it possible that the crank pulley isn't seated correctly and is causing excessive vibration?

 

 

Other known history

 

The engine was new (replaced by Caterham) at 18,000 miles, I don't know if it was a short or complete engine, perhaps Caterham could provide the answer.

 

There was a mention of a head problem at the Hungaroring in 2000 when Paul Hortop owned the car but I don't know if this was before or after the engine was replaced. to my knowledge the Cam belt wasn't changed during the previous owner's time (Steve Jetley) and it certainly wasn't done while I had the car.

 

I believe that Steve did about 10k of the miles (mixed road and track) and I did 3k or so (mainly track)

 

I know Steve didn't have any serious work done, just servicing. I'm waiting for a call from somebody who knows more about the cars history and will post as appropriate

 

 

regards

 

Mark

[masha]

Thanks Mark, that's helpful info, will fwd to Gareth. Minister have said they'd have a look if I can get the car to them which I'll try to arrange over the next couple of weeks. Obviously a bit of further head-scratching & inspection but we're convinced at present its linked to a worn locating lug on the crank shaft pulley, and will next try replacing all the parts on the front of this pulley at the bottom-end (when I can get the parts cheaply). Clearly your theory about the alternator vibration may be true as during the cambelt change we found the bottom bolt much looser than expected. Similarly the angle of head and the skimming discussed above could be another issue causing the cam pulley to be running at an angle (hopefully not though as that is expensive to put right). Whatever, I'm sure we'll get our heads around it and sort it hopefully without it getting too expensive, as it is, its going to be off the road for a few weeks now, but I've got a trailer I can borrow, just waiting on a tow-bar for one of our everyday cars.

 

Not to worry these things are sent to try us.

kind regards, and thanks to you all today for your input, appreciated.

Matthew (& Gareth)