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Timing Belt Tensioner Advice Needed


MarkandCath
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I am bench servicing a replacement engine before I drop in in, it is the 1.0 AUC.

I am using a Dayco kit, KTB341, and the slot in the tensioner is around the bolt as it should be.

When I set the tensioner using the allen key the pointer lines up to the middle of the slot as it should and I nip it up with a spanner. When I go to torque it to 20NM the action of tightened to bolt moves the needle to way over tight. I have tried holding it with the allen key but to no avail.

The only way I found to do it was slacken of the bolt enough so it started to slip back and then nip it up again. I have never had this much trouble with a tensioner before and it worries me.

I can now turn the engine with a spanner and the pointer is in the correct place (middle of the slot) and as per the Dayco instructions. I can press the belt along the run between the crank and cam and the pointer goes of the scale but turning the engine with a spanner brings it back into the slot.

All appears well but all that messing to set a tensioner makes me nervous.

Finally the belt runs right on the edge of the tensioner wheel and I mean totally flush. Is there meant to be a spacer washer between the block and the tensioner? If there was it would fix the problem with the belt being perilously close to the edge of the wheel and it may be why it won't tension very easily.

Cheers All.

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Never done one of these on a Lupo, but if it's anything like other Vee dubs, you need to make sure that the bolt centre pivot runs under instead of over the centre. God it's really hard to describe.

One way, tightening it will tighten the belt, the other way will loosen it. It's an eccentric cam type arrangement, where the centre of the cam is the pivot. You know you have it the right way round if you have it only loosely tightened it gets looser (is that a word) when you apply more tensioning force on the belt. If it gets tighter, you need to rotate the cam about 300 degrees so it goes from below.

Sounds like it's ok now though, so leave it alone!. But it shouldn't run right up against the edge. The belt should fit right in the middle of the pulley. The tooth face of the pulley is curved so that it forces the belt to run along the centre line (like old steam engine belts)...

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In case anyone else gets the problem it is dead simple and I spotted it from looking at Jake's guide. http://forums.clublupo.co.uk/index.php?showtopic=89324&pid=1036868&st=0entry1036868

The muppet that last changed the timing belt had missed of the washer between the bolt and the tensioner. When you replace the washer it tightens the bolt fine and doesn't mess with the setting.

Simple things always create the most problems.

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