well it ended up to be a bad serpentine coupler pulley under the air conditioner. the bearing was rattling.

great repair by the local volvo dealer.

on another site it was mentioned the decoupler pulley on the belt (serpentine) side is bad if you cannot rotate the air compressor pulley in one direction when the engine is not running. would someone who has a pre 2011 xc90 3.2 try that and report back if your ac pulley free wheels when spun backwa...

found on other sites there are two decoupler pulleys - one on the alternator and the other on the serpentine belt side that can make the noise I am hearing.

not sure how to determine which one is failing.

I see on other forms the two decoupler pulleys can make this noise. one on the alternator and the other on the lower serpentine at thge rear end assembly drive (READ).

from what is posted on various sites, sounds like this noise may be a faulty alternator decoupler pulley. appears the alternator must free wheel in the unloaded direction. the noise is coming from the coupler block area.

well replaced the tensioner and idler pulley, and the engine noise returned. the stéthoscope does not reveal noise from the water pump or power steering.

stumped at the moment...

removed the belt tensioner, started the engine with no load on the coupler drive except the alternator and the noise is now gone. the tensioner bearing is not terrible by the spin test. I saw abscape suggested isolating the tensioner on another forum. Thank you! napa has the tensioner, pulley and au...

I've narrowed it down to bad serpentine belt tensioner bearing or noise from the coupler that drives the alternator housing. used a stéthoscope to determine this.

as suggested will remove the serpentine belt to isolate the belt tensioner.

matthew1 wrote: ↑06 Aug 2024, 09:48 Make the video public. It's set to private currently.

I set it to public. thank you.

developed an engine noise. I was thinking this could be an idler bearing but sounds deeper inside the engine. replaced water pump serpentine and idler wheels and tensioner about 20k ago.




any ideas of what is causing this?