Technical JTD105 Cambelt Change Timing Belt tension

[JTDLee]

Hello all. Need a more experienced mechanics opinion:

I have just done the cambelt on my '99 marea JTD105

I am a tad confused: how do I know when the tension is right? jtdsteve says line the arrow up with the index hole in the slider bracket. This is nearly where the tensioner was positioned with the old belt on. I took the tensioner off, then the belt, and renewed the belt and put the tensioner back on in the same position. BUT I found when I cranked the motor over 2 revolutions, the tensioner moved (the internal spring) and the belt jumped a tooth. Belt off, timing marks repositioned then took up slack with tensioner, this time putting it much tighter and farther accross than it was with the old belt. Cranked it over and it didn't jump this time. Felt the belt: between the camshaft sprocket and the sprocket driving the fuel pump, the belt can be depressed about 6mm, and the same in the other places where the tension can be felt.

IS THIS TOO TIGHT, or OK?

The car runs fine, and the tensioner bearing seems pretty quiet. But I am baffled as to why the tensioner is now much further left (about 1cm along the slider) and therefore tighter than it was with the old belt, in order to take up enough slack to avoid tooth jumping. CAN ANYONE ADVISE?

ALSO, for future DIY reference I advise a few considerations when following jtdsteve's very useful post https://www.fiatforum.com/marea-technical/74018-jtd-110-cambelt.html I did not use a kit, I see absolutely no use for it. Before old belt off: The marker on the Cam sprocket is perfectly clear and has a corresponding pointy triangle at 1 o'clock on the engine casing. With this aligned, I then made 3 pen marks on the crank pulley with one corresponding to the notch beneath it in the engine casing, and made two more marks at 9 and 3 o'clock with corresponding pen marks on the casing beyond.

In this way, it is quite possible to see if the belt is on right if the marks all line up again after 2 revolutions cranking by hand.

But the bit about: "12) Adjust tensioner so the little pointer points at the index hole above the slot, and lock in place. 25Nm, & new nut or threadlock recommended!" Made no sense to me, as with the tensioner like that, the belt was far too slack. Strange.

Apart from these points, and that the fitment of Ribe bolts throughout by fiat is ****ing ridiculous, jtdsteve's advice is very sound.


Anyway, any thoughts on this matter are very welcome.

Cheers,
Lee.

 

[Kev_marea]

I'm surprised at the figure of 25Nm, because (as I understand it) the 1.9 and 2.4 TD are set to 50Nm.

Mind you it is described as "Timing belt tensioner fixing bolt - M10" All I saw was a 13mm nut (which indicates it was M8) I tightened the tensioner to 50Nm on mine. I saw no M10 bolt except the engine connection rod mounting bolts (which were all 50Nm too).......Maybe I overtightened my tensioner?

Looking further up the list of torque values - I see
"Belt tensioner to engine mounting fixing bolt" M8 25Nm, M10 50Nm but this is not listed as applying to the the TD 75 or 2.4 TD. It is only listed as applying to 2.0l 20V petrol model. And I just realised this could be referring to the Alternator belt tensioner.

And to further confuse matters the timing belt tensioners for 1370 12V, 1547 16V & 1781 16V are all listed as
"Timing Belt tensioner fixing, nut for bolt - M8 25Nm"

And for the 1547 16V
"Timing tensioner bearing to cylinder head fixing bolt M12 87Nm

I couldn't see any reference to a JTD 105 engine.


But torque values aside, I found with mine (Marea 1910 100-TD) that the tensioner arrow pointed to the circle and the belt was as tight as it needed to be. You have to get the belt between camsprocket and fuel pump sprocket on 1st IMO, and you have to get it as tight as you can, (you should count the teeth between two marks before you take the old belt off).

Did you compare both belts? same length and same number of teeth? before fitting.

Where is your pointer pointing now? sounds like it might be above the circle. Could it be the wrong belt?

 

[JTDLee]

Cheers for your reply.

Definately right belt, same teeth, length, numbers.

With the arrow pointing at hole in the slot, the belt is really loose. The hole is now a good 1.5cm from the end of the arrow, and the motor has done 250 miles with no funny noises or any probelms...

Rather confusing though. I tightened the tensioner nut to 50nm too, 25 seemed too little.

I'm going to get a fiat dude to check the belt tension in a week or so.

 

[NumanR]

You should always replace the cam belt AND tensioner as the tensioners can be a cause of premature failure. Alot of so called garages do not change the auto tensioner to keep the prices down but it is not a good idea. If your tensioner does not tighten to the correct tension when the marks line up it is faulty and should be replaced.

 

[Kev_marea]

I thought you might be confused because I noticed you said "hole in slot"... so here is a picture. You see the pointer is pointing at the hole above the slot, and you lever on the upstanding bit pointed to by the arrow to achieve this.... and on my car there was a small recess in the engine block behind the upstanding part where you could insert a screwdriver to get a hold to lever against, I then filled the space I created (by levering) in the recess with something solid, to enable me to lever again with the screwdriver this time levering against the "something solid" bit that I had put into the gap.
Oh and just to confuse things, on my car there was no hole, just a circle etched into the rear plate.

 

[JTDLee]

Nice one Kev, it all becomes clear now. I think my arrow must be pretty close to that position, but I've decided to put a new tensioner on it anyway so I'll set it properly then.

 

[Kev_marea]

Cool , glad we got that sorted.
Let me know how much the tensioner costs...

 

[JTDLee]

Cool , glad we got that sorted.
Let me know how much the tensioner costs...

Well, I never did re check the tensioner arrow. But realised I thought the hole it said to point it to is very small, and I didn't see it, and I presumed it meant the slot in the bracket itself. Anyhow, tension must be ok, as 25,000 more miles have passed without incident.

I plan to do the Cam Belt every 45k to be on the safe side, and just got a new one off ebay for £12 including postage. Bonza! Clutch next.....