/// John has the right idea. There are plugs on these engines that will whistle with a small air leak. Go to a hardware store and buy stiff polubutyl and fexible vinyl to make an earphone. Spray carb cleaner on manifold gaskets etc. to locate leaks.

If your belts are out of line from alternator mounting bushings being worn there may be a spray of worn belt material on the inner fender just even with the alternator pulley.

Do not use anything except belt dressing on "V" belts. It is available in spray cans. It will get you by for a few days if the problem is worn, slipping, belts. Test the alternator bearing by releasing the belt pressure at the alternator adjustment. The alternator will stop and the bearing cannot make noise stopped. Before releasing the alternator test the belt at the alternator by pushing on one of the alternator cooling fan fins (with the engine stopped). If you can turn the alternator by hand the belt is problably bad.

I would straight down onto the belts and see if they have a slight turn to them as they get near the alternator, the power sterring pump and the AC. I think it may be the bushings that mount these units to their respective brackets. The slight misailignment does cause teh belts to sqeel sometimes. With the weather changing colder (where I'm from anyway) it could cause these symptoms to crop up on both cars, same time.

I have 158K on my '89 200, and I did my bushings 4 months ago. Before I did it, I would loosen the pivoting bolts and tweek the alternator straight then tighten it down...It works for a while.

PS With 158K, I have not replaced my water pump or anything else and they are still running quiet. I'm guessing belt issues.

Put some kitchen soap on the belts and see if the Whistle stops. that will eliminate bearing noise if it does.

I have experienced the "whistle".....turned out to be the alternator. Either a rebuild with new bearings/brushes/etc or replacement with a new/rebuilt unit PLUS new rubber/poly accessory mounts seems to cure it. I know this was a "shotgun" cure...because I never actually knew the root cause within the alternator or mounts!! Try listening with a stick or spraying some silicone lube on the mounts.....

I have an '87 240 (b230f/m47) with 142K miles. At start up in cold weather (has been in the 30's recently) it makes a whistling/whinning sound that increases frequency as the idle is increased. I'm suspecting the water pump just because I haven't replaced it yet (have owned the car over a year, 10K miles) but I don't know what a Volvo water pump sounds like when it's going bad. I know a Ford WP, which is a lot louder than what I have. After it warms up, the noise goes away. I also have a power steering belt squeal, but that is loud and recognizable. The strangest noise my car makes is at highway speed (65-80mph), and can be described as a high frequency metallic vibration. One of the nuts on the exhaust manifold is not completely tight, and the washer is able to move and vibrate. I consider most of the noises normal on a 13 year old car.