I've been getting this wavering high-pitched squealing noise from the Belt area of the car at start-up. It pretty much goes away when you rev the car past 2000rpm. It goes away usually after the car has been driven for a while. Now, I bought this car with a blown headgasket for $20 from a guy. I use to be a Professional Volvo technician at a local independent repair shop here in Cincinnati just last year. I rebuilt the head, replaced the timing belt, serp-belt. I have not replaced the timing-belt tensioner or idler pulley and fear that one of them is what the noise is. It is the old hydraulic style. I'm going to remove the serpentine belt tomorrow and listen to see if it goes away or not. The water-pump is not leaking and actually I have NO leaks at all from anywhere on the car except slightly from the steering rack. I'm considering taking a video with audio and posting it on youtube. Is anyone interested in hearing the noise to hear what I'm talking about. It is quite interesting. I'm going to replace the timing belt tensioner pulley and idler anyway since I'm confident they are the original pulleys. Does anyone have any input on what they think the noise is from? I've seen these pulleys lock up on a number of Volvo cars, not a good thing AT ALL.

 

I have a squeak every once in a while that I have been told is an idler pulley in the serpentine belt system.

 

Yeah, I believe after I take the serp belt off and start it I'll be able to determine if its in the accessory system or in the timing belt system. I'll let you know what I discover.

BTW - Whats the link for the AUX input mod? I have the premium sound system and I am tired of hauling CDS around, lol.

 

My bet is on the idler roller. Could be the tensioner roller. Anywho, failure will cost you a head. Not worth the risk. Reving it is not a good idea. LOL Caught one just in time on my 960.
Timing belt replacement instructions on a 1997 Volvo 960

Here is the link to the mp3 adapter mod. The sound is so clear it's sick. I did not install resisters so I have to turn the sound down on my phone/mp3 player. I'm kinda afraid I'm going to blow my speakers.
Radio mp3 Modification for the Volvo SC-813, SC-815 and SC-816 Car Stereo

 

I've seen some S90s and 960s with the locked up idler rollers and dead and towed into the back of the shop. I can drive my car and the noise goes away, but you're right don't want to play with C4. I'd hate to see my $20 car go boom, especially since I put so much work into it to to make it right again.

 

My mechanic says the squeaking idler pulley in my car is in the serpentine belt system, not the timing belt system.

I'm not worried at all about it. It squeaks only on the rare occasion, very faintly, and then goes away.

 

YES, the idler roller on the accessory drive system could very well be bad. The accessory belt drive has the following pulleys: idler, tensioner, crank, p/s pump, alternator, A/C compressor on an 850.

The timingbelt system has the following pulleys and sprockets:

Intake, Exhaust, Crank, Water Pump, Tensioner, Idler

If you take the serpentine belt off and run the car with it off and the noise does not go away its in the timing belt system, (tensioner pulley or idler pulley)

Otherwise, check the Idler, Tensioner for smooth operation, noise, looseness and tight spots by spinning them. I've never seen one power steering pump go bad (that always had adequate fluid), compressor clutch bearings can go bad (usually roller coaster noise), as well possibly alternator (not ever usually). Also, from my recent check out with fixing this problem I noticed the water pump bearing is still smooth and the pump is not leaking (230k+)

 

And did you do this on your car and did you find out what is making the noise ??

 

Well, in the name of Halloween and resurrection, thread back from the dead! I fixed the problem today. A couple of days ago I took the serpentine belt off and ran the car and it still had the squeaky noise from the belts area. I took the timing belt off and first spun the tensioner roller. It was noisy and needed replaced but wasn't the problem. I took the serpentine belt tensioner off to have a look at the timing belt idler pulley and it was almost impossible to spin a complete 360. It was locked up. The last few days the noise was getting worse and I would hear it most of the time. I sure didn't think it was the belt just sliding over the idler squealing. I'm very surprised that the belt didn't shred or break. Anyway I was very lucky to say the least. I put the belt on new last year and it actually STILL looks great for what it has been through recently (Contitech). I'm going to replace the belt later on next year sometime anyway since it definitely lost a little rubber. I replaced the idler and the tensioner roller and put it all back together. Now it is as quiet as a mouse and runs great for a 230k+ (odo gear broke) 855.

Oh, and just like rspi said, don't take a chance on timing belt parts. My valves are very lucky to survive this ordeal. Usually the belt will break and sadly it's over for most people at that point ($$$$).

 

Glad you kept digging. Congrats!!!