Hi All,


I'm replacing the cambelt on my seicento. It's all gone on ok but when I run the engine, there seems to be a lot of slack. I've tried moving the tensioner but it's as far as it will go. The belt is made by Dayco, it matches the previous belt (ie same length and amount of teeth), the box is labelled up correctly but the timing marks don't line up.


Does anyone else have a dayco belt fitted or any idea what's going wrong?


Thanks

Forget the marks (if any) on the belt. Use the ones on the cam and crank pulleys.

Are you turning the adjuster the right way? It has a sort of cam action on the central bit (the holes are for the "special tool", but a screwdriver can be used. Ideally, replace the tensioner bearing at ther same time as the belt (they take a real hammering).

I think so... I've moved the tensioner as far as I can towards the front of the engine bay & then tightened up the bolt. So does it then have some extra movement in it, if you can get the tool/ screwdriver into place?

Something like a pair of cranked needlenose pliers will do the job. There's something like 2" of adjustment in the adjuster. Just turn and hold it by the two holes.

it will only take slack out of the back side... perhaps you have not got the belt from the top pulley down round the water pump and then the crank tight enough, if you have slack there the tensioner won't take it up and then after one revolution of the engine the tension of the belt equalises all the way round.... start putting the belt on the cam pulley and then hold that with one hand and pull the belt as tight as you can while you go down round the pump and crank, the belt will be pretty slack at the back and take that up with the tensioner. After that turn the engine through a few complete revolutions by hand (turning by the crank) then check the timing marks all still fully aligned.

I use a pair of circlip pliers on the tensioner myself

I have the same problem. I take the slack out of the belt and then pinch the nut up. But the final tightening of the nut puts the tension out so its too slack.

Should the nut on the tensioner be a flanged nut like on mine or a separate nut and washer?

The manual shows a separate nut and washer.

I also have a problem that when I do get the belt to the correct tension and the engine gets hot the belt becomes too tight. Is it normal for these belts to shrink when they get hot?

Logically, the belt should expand when hot!

Flanged bolt or bolt and washer makes no difference (manufacturers use flanged bolts mainly because it speeds up automated production).

The 90 degree test will always be a bit hit and miss, but the belt isn't that fussy. A FIAT dealership will either use the old FIAT/Alfa "weight on a stick" tool or a more modern one which checks the frequency the belt vibrates at.