Aux belt tension

[Agour]

Hi all!

I've just replaced the alternator belt on my c5 mk3 tourer and it was tough to get on.

It felt like the belt was shorter than the one I took off, although laid side by side they seemed the same.

Does anyone have a workshop manual and can check the correct tension for the belt?

It's an auto adjustor, but I want to make sure I haven't got the wrong belt on.

I suspect the one that came off was a cheap and incorrect one.. (it has started wearing pretty fast)

Thanks!

[GiveMeABreak]

There is no tension measurement for the belt that's why it has a dynamic tensioner. I take you compressed the dynamic tensioner in the anti-clockwise direction before pegging the dynamic tensioner - before removing the belt and then progressively decompressed the dynamic tensioner to tension the accessories belt after refitting?

[wheeler]

New belts generally always feel tighter to put on, the old belt will have stretched slightly for a start & the rubber on the old worn belt will be much more pliable than a new one.

[Agour]

There is no tension measurement for the belt that's why it has a dynamic tensioner. I take you compressed the dynamic tensioner in the anti-clockwise direction before pegging the dynamic tensioner - before removing the belt and then progressively decompressed the dynamic tensioner to tension the accessories belt after refitting?

By pegging, do you mean holding it in place somehow?
I couldn't see a safe way to do that, so turned the tensioner anti clockwise, whipped belt off, then let the tensioner slowly go. Then just the same thing for installation.

I just had to put (what felt like) a fair bit more pressure on the tensioner to get it loose enough to fit the new belt.

[GiveMeABreak]

These are the tools:

[1] Dynamic tensioner compression lever.
[2] 4 mm diameter pin.

Procedure is:

Compress the dynamic tensioner (1) in the anti-clockwise direction (as "b") using tool [1].
Peg the dynamic tensioner (1) at "a" using tool [2].
Remove the accessories drive belt (2).

Check that the roller (1) turns freely (no play or tight spot).

Refitting

Refit the ancillary belt (Observe the following order):

• Accessories drive pulley
• Compressor
• Alternator
• Roller tensioner

Make sure that the accessories drive belt is correctly positioned in the grooves of the different pulleys.

Support the dynamic roller tensioner (1) (as "b") using tool [1].
Remove the pegging tool [2].
Progressively decompress the dynamic tensioner to tension the accessories belt.

[wheeler]

Trust me, its almost always tighter to fit a brand new belt on for the reasons ive said above. I have fitted literally hundreds of serpentine belts. Sometimes they are that tight that you end up needing to rotate the engine by hand to draw the belt on.
As for the pegging, this is not actually necessary, it just makes it way easier, especially if you are doing it by yourself. All the peg is doing is holding the tensioner back for you & acting like a 3rd hand, it has nothing to do with the actual tensioning. The peg is nothing fancy, I normally just use an Allen key