I have been trying to seek out an answer for a good while on this one-

I have strong belt noise on my 90 240DL Wagon. I have been trying to track down the noise for some time.

The noise seems to occur more when the engine is cold and rested but has sometimes popped up after normal running. It will contuine until it feels like something catches- if said "catch" does not take place at slower speeds it ensues even into fourth- if I decelerate the noise dampens and often that is when the "catch" seems to take place. While the noise is present the car seems to not be getting all of its horsepower, it is availble but seems to be delayed- when I punch the pedal it takes a split second to react where as when the noise is not present it reacts flawlessly.

The car has 179K+ on it now- only has two belts now as the AC Compressor went bye bye a few years back and neither belt is showing dramtic wear.

I suspect it could be the fan clutch but I have been told that those almost never go bad- the other thing I have considered is the Alternators Key- I did have it replaced and the noise went away for a few weeks but has now come back and I have not checked to see if the replacement is still in good condition.

Any thoughts?

Aside from worn belts there are a few likely causes of squeak/squeal from those systems.

1) Bad bearings in water pump or alternator. Probably the easiest way to find that is to remove belts and look for play in the pulley shafts.

2) Alternator not mounted parallel with the motor's axis. Crooked. Due to worn alternator mount bushings. There are three of them, they cost about $1 each at fcpgroton.com. Pretty much requires dismounting the alt to change out the bushings.

3) Main crank pulley's inner rubber ring has lost the bond to metal and so the drive pulley is forward or rearward of it's proper location. Causes belt to run crooked which makes it squeal. You'll need to replace the pulley which is a harmonic damper pulley. The pulley is a 3-part assembly; the middle ring is rubber to damp out vibrations.

2 + 3 above both involve the belts running crooked causing squeal. Viewing the belts from above you can see if they're running crooked. You have to look at the alternator to see if it's sitting crooked. If you have another Volvo 240 or 740 handy you can see its crank pulley and see if it's forward or rearward in comparison to yours.

A moving crank pulley is not a good thing. There was a post here a couple months ago where one went out through the radiator. I had one that moved backward into the timing belt; I had to get a new timing belt in addition to the pulley and timing belt covers.
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Sven: '89 245 NA, 951 ECU, open-front airbox, E-fan, 205/65-15's, IPD sways, E-Codes, amber front corner reflectors, quad horns, tach, small clock. Wifemobile '89 245 NA stock. 90 244 NA spare, runs.