I'm working on replacing the timing belt, TB tensioner/idler, serpentine belt and serpentine belt tensioner on my 2012 s60 t5 with 90k miles. I've read the issues on this forum regarding serpentine belt shredding pieces which end up in the timing belt area and then affecting the timing belt. So I wanted to replace all these parts and awaiting shipment of parts. Before I tried to start this work, I noticed an odd squeeling type sound in the engine bay. I had recently replaced sparkplugs and the Pcv diaphragm that's in the oil filter separator box because the diaphragm was torn and I was getting a loud whisting sound from the engine bay. Replacing the diaphragm fixed the whistling sound but now I have a squeeling sound. The sound made me very nervous and I shut off the car soon after starting it after the spark plug and pcv diaphragm replacement.

To diagnose the sound further, I removed the serpentine belt and serp belt tensioner. The belt seemed to riding on the tensioner. I didn't notice it starting to come off as mentioned in some cautionary posts here. I also removed the timing belt covers and noticed that belt riding too close to the edge of the camshaft. In addition, I spun the serp belt tensioner and alternator pulley by hand to try to hear any noise but didn't notice any noise.

Anyways, long story short, to further diagnose the sound, I was thinking to start the car while I have the serp belt off. I wanted to rule out the noise coming from the alternator pulley, serp belt tensioner, or the idler pulley. If I still get the sound, it might lead me towards the timing components which I'll be replacing (except waterpump). Is it ok to start up the car this way? I'd only run it for less than a minute since the alternator won't be running. And I'll charge up the battery via battery tender to make sure it's full.

 

Get a can of belt dressing from your local auto parts store. Will tell you if it's the belt or something else. I would not run it without the belt.

 

Thanks for the input. I didn't know there was something called belt dressing. The replacement parts should be here tomorrow so I think I'll replace them and see if the noise goes away. I was going to replace the parts regardless. Then I'll diagnose further by using the dressing. Would the dressing be able to point out pulley noise such as the alternator pulley? Even though that pulley seems to spin fine when spun by hand, I wonder if at higher speeds it'll make noise.

 

Just got done replacing the timing belt, timing belt tensioner and idler, and serpentine belt and tensioner. Test drove the car no more noise. So must have been one of those components going bad.