Well I'm actually not new but haven't been on the forum for ages (years !) so had to start over.

Volvo owner for decades : 940 TD, then V70 TDI (VW engine) and currently an XC70 D5 which I love but now has 308 000 km on the clock and has had more than its fair share of problems... all of which I've fixed myself.

However the latest one is getting me desperate and perhaps someone could help : vibrating serpentine belt.

This isn't the first time the issue has been discussed so I'm reverting to an old thread from Goodyear1 in 2008.
This exactly describes the problem I have. "V70 D5 2002 - horrible noise from belt/one of the pulleys on tick over. Sounds like a badly rumbling bearing with occasional ticking noise. On tick over the tensioner is vibrating and the forward long vertical run on the belt oscillates by half an inch (ie. it appears loose). When the AC compressor kicks in or the alternator is loaded eg. by turning on heated screen, seats etc., the belt flaps about even more. If the engine revs are increased even slightly, the belt tightensand the noise seems to disappear. The belt is tight when the engine is off.

So if anybody has any ideas please see revived thread.

 

so what's involved with the serpentine belt in question? Tensioner, Idler, crank pulley, AC compressor, alternator, power steering pump (?) - Normal servicing would be to replace the belt and idlers but you can also replace the tensioner. Once done that leaves you the AC, alternator and possibly the ps pump and crank pulley. Did you try pulling off the belt and feeling each by hand? Did you inspect the pulleys for wear or alignment (wobble?)? The other thing that may be involved is the motor mounts and timing belt. If you've already serviced these then either you need to consider you may have a bad part (or wrong part). I was a bit confused reading the old thread as to what was referring to what you've done vs what the original thread owner did. Are you doing your own work or are you mostly trying to determine what your tech's plan of action should be? Note - nothing here is specific to Volvos so I'd think a competent tech should be able to work through the triage process.