Technical Cam belt alignment problem

[mreurostar]

I have a2019 ducato which I have changed the cam belt and water pump. All went well u till I rotated the engine several times and noticed the belt was slipping towards the outside edge of the pulleys and also continued to slip over the edge. I then tried removing the belt and water pump and reinstalled them. After re over tensioning and rotating and resetting the tension, it seemed better. I reassembled the cover and auxiliary pulley and alternator belt and ran the engine. All OK for 10 mins or so then I could hear the cam belt rubbing on the cover. Does anyone know if there is a pulley alignment proceedure or suggestion to stop the belt creeping off the pulleys.

 

[Googlebot]

Sounds like something isn’t straight, did you replace the tensioners?

 

[mreurostar]

Yes, I replaced idler pulley, tensioner, water pump and housing and cam belt. I just wondered if there was some way to align the belt path. It is the full Gates kit KP15592XS that I used and should be excellent quality.

 

[Googlebot]

Yes, I replaced idler pulley, tensioner, water pump and housing and cam belt. I just wondered if there was some way to align the belt path. It is the full Gates kit KP15592XS that I used and should be excellent quality.

That would suggest then that something is worn or not aligned correctly.

Have you checked all pulleys for any play?

Is the timing cover on properly?

To my knowledge, the belt doesn’t need aligning. Others can confirm who know far more than me.

Hope you find the cause.

 

[mreurostar]

Nothing worn. New pulleys fitted and tensioned OK with no play. I can not see any way to adjust anything. I have now written to the seller of the kit as it says in the sales literature that they will help. Maybe they will replace the kit as faulty. We will see.

 

[Communicator]

I did wonder whether the guide rollers should have a slight barrel shape, to keep the belt centered. (This technique is used in flat belt drives.) However, careful examination of a couple of old rollers does not reveal any barrel shape.

 

[mreurostar]

I did think the same. Anyway, the company that sold me the kit have come back to me and they want the whole kit removing and returning to them who would forward it to the manufacturer to test and check it. They quote a time of 8 to 12 weeks after I have removed and sent ot to them before I hear the outcome. As I go to Portugal 8 weeks today, that ain't happening so I am going to try substituting the old pulley and tensioner to see if that proves anything. Fingers crossed.

 

[Reg 65]

Like many others I suppose, I have not replied because I don't know the answer, but are very interested in this so please keep us posted.
As Communicator says flat belts stay on because of 'crowned pulleys' the pulley has a very slight crown in the centre tapering off to either side. So slight you probably won't be able to see it - especially when its fitted - but you could try holding a flat edge against each one when you have got them off?

As an afterthought are the centres the same so they stick out as far and are aligned? (Remember to mark each one if you can't see which is which!!)
Maybe another possibility is if one side of the new belt is very slightly longer than the other?

 

[Communicator]

Like many others I suppose, I have not replied because I don't know the answer, but are very interested in this so please keep us posted.
As Communicator says flat belts stay on because of 'crowned pulleys' the pulley has a very slight crown in the centre tapering off to either side. So slight you probably won't be able to see it - especially when its fitted - but you could try holding a flat edge against each one when you have got them off?

As an afterthought are the centres the same so they stick out as far and are aligned? (Remember to mark each one if you can't see which is which!!)
Maybe another possibility is if one side of the new belt is very slightly longer than the other?

That is what I did with a used pair of rollers. I did consider using digital calipers, but the rule was much closer to hand. I could not detect any barrel shape, with rule and roller held up to the light. I do have another pair of lightly used rollers..........