Noisy aux belt tensioner c5x7

[aerodynamica]

Hi all, C5 2.0 Hdi auto. I've noticed a lot of noise from the alternator area upon start up - at its worst when fans, lights etc are on.

Aux belt new only few months ago and I thought the alternator was failing but now I'm sure the noise is actually the belt tensioner below the alternator. Can see it shaking slightly with the noise.

I recall it has a stiff spring to push the tension but can't recall if it was locked after tensioning like on cambelt. Anyone know if the tensioner is meant to shake like this? Is it one of the 'floating ' type?

I really should recall from changing the belt but I've forgotten.

[GiveMeABreak]

Yes, the alternator has a dynamic tensioner and must be locked with a pin prior to changing the belt.

Tensioner at (6)

[aerodynamica]

Hi Marc, thanks for this. I recall the locking of the tensioner to remove the belt ( made a special tool for this) but is there any information on the tensioner itself such as can the spring be adjusted an any way? I realise it's meant to move but the sound it is making sounds a bit wrong. Might need a spray of WD down where the tensioner mount meets the engine block.

[Lenny]

Check the pulley on the alternator.
They're supposed to have like a freewheeling clutch mechanism in them but eventually it fails and makes the belt judder.
Not a bad thing to change (with the right tool).

[aerodynamica]

Oh there's a thought Lenny.

[GiveMeABreak]

No manual adjustment on the dynamic tensioner - as it's supposed to be 'dynamic'. It's compressed first, then pegged as you know, then belt replaced, locking tool removed, then the tensioner slowly decompressed using the tool.

If it's nothing else like the alternator pulley, then I suspect the dynamic tensioner may need replacing.

In anticipation of replacement, the part was superseded, so may be a reason.... anyway the new part number ((6) on the diagram), is 1611424380, £152.88!!

[dulenator]

I had a bad alternator pulley, and the tensioner was jumping like crazy, matching the clicking sound. It looked like the tensioner was going bad, so I changed it, and the new one was doing the same. The alternator pulley fixed the issue.

[aerodynamica]

I had a bad alternator pulley, and the tensioner was jumping like crazy, matching the clicking sound. It looked like the tensioner was going bad, so I changed it, and the new one was doing the same. The alternator pulley fixed the issue.

Thanks, it certainly is the most cost effective solution. I think I will order the pulley clutch to replace and see how that turns out. Alternator output is fine so I suppose the Alternator itself is ok. Thanks again

[nimi62]

Hi

Also had same problem with Jumpy II and tensioner replacement didn't fix the issue.
Car has driven over 300tkm, so seen that alternator replacement as DIY was cost effective solution as new (refurbished VALEO) from Autodoc paid only around 200€.
Alternator had still need to be removed as the belt-clutch was that near the car body that replacement there wasn't possible.

So replaced whole alternator, which fixed also tensioner issue.