Hi guys

Not had much luck in the Punto section with this so I thought I'd ask in a section where they have lots more JTDs

Basically I having problems tensioning my new cam belt. I can't seem to make the tensioner stay at the tension I set. That's with the tensioner bolted fully onto the block. The tensioner is new.

I'm a bit stumped TBH as to why I can't set the tensioner up properly. I have found a pin/dowel on the block which the slit in the tensioner backplate can fit over. Do I use this as a stop for the silver pointer then lever the angled tab to set the tensioner?

TIA

This is the instructions for setting the mobile tensioner from the Stilo JTD 8V eLEARN manual.

Davren said:

This is the instructions for setting the mobile tensioner from the Stilo JTD 8V eLEARN manual.

Click to expand...

Thanks for that. Unfortunately it tells me nothing of why my tensioner will not stay at the tension I set.

If I move the pointer around then fully tighten the tensioner nut, the pointer just springs back to its original position, which is nowhere near the tensioner marks; hence my question of if there is some kind of stop for the pointer to rest against.

I've never fitted one yet but plan on doing my JTD cambelt tomorrow.

I have a new tensioner in front of me and I agree with you, I can't see how it will stay back against the spring tension to be able to fit the new belt over it. Even with the center bolt tightened, it doesn' look as though it will stay back.

I'll have to research this a bit more before doing mine.

To both Dave's ..ie Davren & Chaos..long time no see to the later one..

https://www.fiatforum.com/stilo-guides/204297-fiat-stilo-jtd-cambelt-change.html

Seen that already Phil but it doesn't deal with the problem of holding the mobile tensioner back against it's spring to enable you to get the new belt on. All it says in the guide is "setting up new tensioner is a pain" which looking at the construction of my new tensioner would be correct.


This doesn't appear to be documented anywhere but;

On my new tensioner there's a small hole in the rim of the bearing mounting and a cutout slot in the retaining washer. At rest, the two are not lined up, but once the tensioner is levered to full tension against the spring, it would be possible to insert a small pin (3.1mm dia) through the cutout into the hole. This would hold the tensioner in the correct position (pointer would be lined up with dot) while the belt is fitted.

If that's not what it's for, then there would be no reason to have the small hole and the cutout. It would also be a strange coincedence that if a pin is fitted, the pointer just happens to be in the correct position.

Could also be that different manufacturer's cambelt components are designed differently. I always use Dayco for cambelts so other manufacturer's parts may not be the same.

What you do is put the belt on with the tensioner slack, then push on the little metal black tab you see on the right of daren's tensioner with a screwdriver and tighten the center bolt while holding the metal tab up. It is a 2 person job, one to push on the spring tab from below the car and the other to tighten the center bolt from above.

PNL said:

To both Dave's ..ie Davren & Chaos..long time no see to the later one..

Click to expand...

:wave: How are the eyes Phill?

Davren said:

This doesn't appear to be documented anywhere but;

On my new tensioner there's a small hole in the rim of the bearing mounting and a cutout slot in the retaining washer. At rest, the two are not lined up, but once the tensioner is levered to full tension against the spring, it would be possible to insert a small pin (3.1mm dia) through the cutout into the hole. This would hold the tensioner in the correct position (pointer would be lined up with dot) while the belt is fitted.

If that's not what it's for, then there would be no reason to have the small hole and the cutout. It would also be a strange coincedence that if a pin is fitted, the pointer just happens to be in the correct position.

Could also be that different manufacturer's cambelt components are designed differently. I always use Dayco for cambelts so other manufacturer's parts may not be the same.

Click to expand...

I also have a Dayco tensioner. It's replacing a Dayco tensioner. Another reason for that hole is that seeing the mark on the backplate is very difficult to see with the tensioner in situ.

Applying force to the tensioner spring would take tension off the belt. It's fairly easy to get the belt fully fitted. It's just tensioning it that's the hard part If anything my belt is over tensioned; I can turn it approx a fifth of a turn in the centre of the belt going from the crank sprocket to the tensioner and again about a fifth on the run between the idler and the crank sprocket.

john55 said:

What you do is put the belt on with the tensioner slack, then push on the little metal black tab you see on the right of daren's tensioner with a screwdriver and tighten the center bolt while holding the metal tab up. It is a 2 person job, one to push on the spring tab from below the car and the other to tighten the center bolt from above.

Click to expand...

Hi John. Do you mean push the tab straight upwards? Did the pointer stay where it was after tightening the tensioner nut? If I tighten the tensioner nut as hard as I can, I can still move the arrow pointer around.

Cheers all

@ john55...... If you leave the tensioner slack, you can't get the belt on. You have to push it back against the spring before fitting the belt, then release the spring tension so the toothed outer wheel can tension the belt.

The belt runs down the left side of the toothed wheel in my picture. The tensioner is currently slack and is at it's full extent to the left. Because of the offset fulcrum, when you push the pointer anti-clockwise against the spring, the toothed wheel moves to the right so you can get the belt on.

The problem is holding it there while you fit the belt without needing 2 people to do it.

chaos said:

If I tighten the tensioner nut as hard as I can, I can still move the arrow pointer around.

Click to expand...

It's the same as my tensioner, tightening the center bolt doesn't stop the toothed wheel or pointer moving. It seems as though the full force of the spring must act on the belt permanently once the belt is fitted and pointer released.

Davren said:

@ john55...... If you leave the tensioner slack, you can't get the belt on. You have to push it back against the spring before fitting the belt, then release the spring tension so the toothed outer wheel can tension the belt.

The belt runs down the left side of the toothed wheel in my picture. The tensioner is currently slack and is at it's full extent to the left. Because of the offset fulcrum, when you push the pointer anti-clockwise against the spring, the toothed wheel moves to the right so you can get the belt on.

The problem is holding it there while you fit the belt without needing 2 people to do it.

Click to expand...

You can get the belt on perfectly well with the tensioner as is. I did it easily. The mounting stud (there's some innuendo there...somewhere) for the tensioner is not in a fixed position

Davren said:

It's the same as my tensioner, tightening the center bolt doesn't stop the toothed wheel or pointer moving. It seems as though the full force of the spring must act on the belt permanently once the belt is fitted and pointer released.

Click to expand...

Hmm. I wondering if you set the tensioner's tension correctly then slide the tensioner mounting stud (with the tensioner fitted) as far to the left hand side as you can. Do the nut up properly then let everything go and allow the tensioner to apply force to the belt as you've said.

It doesn't help that the only tensioners we have are from the same manufacturer. Have you had a chance to look at your old tensioner set-up?

chaos said:

It doesn't help that the only tensioners we have are from the same manufacturer. Have you had a chance to look at your old tensioner set-up?

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No, I've not dismantled it yet.

Phoned Dayco technical today 5 times. They say they have a technical bulletin about the tensioner. Three times they've tried to e-mail it to me and twice by fax but I've not received any of them.

If I cant get the info, I may not bother with it. The car had a new cambelt 20,000 miles ago just before I bought it. Only reason I was going to do it again is because they didn't replace the water pump.

This is an active, sprung tensioner. It does not lock into a fixed position and is ment to move. It is helt against the belt by a spring. You have to push the black tab to get the spring to tension, then do the center bolt tight. Mine looked exactly the same and I installed it no problem. I cant quite understand what your problem is.

john55 said:

This is an active, sprung tensioner. It does not lock into a fixed position and is ment to move. It is helt against the belt by a spring. You have to push the black tab to get the spring to tension, then do the center bolt tight. Mine looked exactly the same and I installed it no problem. I cant quite understand what your problem is.

Click to expand...

Did the tensioner pointer move when you let go of it?

chaos said:

Did the tensioner pointer move when you let go of it?

Click to expand...

What exactly do you mean by the tensioner pointer?
The black tab on the right should not move once the bolt is tightened. The dot and silver tabs as arowed will move in relation to each other as the spring tightens / slackens. I believe the two tabs pointing down in the photo should not move when the bolt is tightened but mine did not have these.

One issue I did come across was the bolt was the wrong length. I fitted a genuine fiat kit on my car which had an aftermarket kit fitted previously and I had to go to Fiat to buy the center bolt seperately for one of the tensioners as the aftermarket one used a shorter bolt than the fiat tensioner. Maybe the bolt is too long and hitting the end of its hole before clamping down on the tensioner which is leaving it loose.

john55 said:

What exactly do you mean by the tensioner pointer?
The black tab on the right should not move once the bolt is tightened. The dot and silver tabs as arowed will move in relation to each other as the spring tightens / slackens. I believe the two tabs pointing down in the photo should not move when the bolt is tightened but mine did not have these.

One issue I did come across was the bolt was the wrong length. I fitted a genuine fiat kit on my car which had an aftermarket kit fitted previously and I had to go to Fiat to buy the center bolt seperately for one of the tensioners as the aftermarket one used a shorter bolt than the fiat tensioner. Maybe the bolt is too long and hitting the end of its hole before clamping down on the tensioner which is leaving it loose.

Click to expand...

By the tensioner pointer I mean the silver arrow to the right of the toothed tensioner wheel. In Davren's pic, this pointer is pointing at the black tab on the tensioner backplate.

I think I'll see if bolt length is an issue for me by bolting the old tensioner to a lump of wood.

chaos said:

I think I'll see if bolt length is an issue for me by bolting the old tensioner to a lump of wood.

Click to expand...

Tried it. With the tensioner bolted as tight as I can (the backplate is bolted tightly to the piece of wood; I can't move it); I can still move the pointer around i.e. I can still tension the spring and move the toothed wheel fore and aft. In Davren's pic the hole that is arrowed moves with the tensioner pointer. The second arrowed bit on the right hand side (the tabbed bit) remains in place.

Thanks for all the help so far guys

Finally got the bulletin from Dayco, it's not much different to the Fiat instructions though.

Dissmantled mine yesterday but not refitted anything yet, doing it tomorrow. I think the tensioner looks illogical in the hand but suspect it will look more logical once refitted.

No matter where I lever the black tab, no matter what direction, or which way the backplate sits on the engine block, I still can't get the bloody marks to line up. It's nowhere near.

Also where should the pin (which is part of the engine block) be in relation to the tensioner back plate?