Fan Belt

When it is cold out and sometimes when it isnt the fan for my climate control makes a rattling / squeking noise. It goes away if I manually change the speed higher but otherwise when it is around 0 or negative
it usually does this.
Also When I back my car up it makes a screeching noise sometimes... Another member said they thought this was a fan belt that needed to be tightened... Any thoughts on that? Maybe the two are related?
Also does anyone know how to go about tightening these? I have a 02 325i
Thanks!
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It is likely that the cause of your first problem is a noisy fan motor. These things can be hard to replace.
You do not tighten belts on cars of recent vintage. There is a spring loaded pulley which controls the belt tension. It might be that the strength of the spring can be adjusted. However, usually you replace the pulley. Another cause of this noise is that the belt is near the end of its life.
Jim
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Anything I can look at / fix myself?
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Anything I can look at / fix myself?
You might be able to tell if the belt shows evidence of wear. I don't believe I could though. A qualified mechanic can tell you if the belt is tight enough. Jim
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Have a look at the Fan Belt Idler Pulley. My '97 323i had your problem an I took the pulley off and when spun by hand it rattled. I injected some oil into the back of the bearing as a quick fix. This cured it but it is only a temporary fix as it will soon dry out and the rattle / squeal will come back. Mind you that was 500 km ago! I got a new pulley/bearing assy but haven't put it on yet.
Fred
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On the 6 cyls it's usually the pulley. My 2001 does it.
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I'd say it's difficult. They can show external signs of cracking quite early on but last for a long long time like that. Best to go by mileage.

The likely signs are slipping noises from the belt when the alternator is working hard - like after a cold start in winter. Of course it might do this if correctly tensioned but contaminated with oil, etc.
--
*Frankly, scallop, I don't give a clam

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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You are describing separate issues.
The fan motor for the life support system (ventilation system) might make a rattle noise that can come from a leaf that has fallen into the intake duct. Open the hood, and at the bottom of the windshield there is a set of three or four twist thingies that will open a cover. Under this cover is the cabin air filter -- also called the microfilter -- and you can simply lift this filter out and check the inside of the cavity for foreign objects.
The screeching noise when you back up can be any number of things. You asked about the fan belt, but this would make noise without regard to gear selection, and would make noise upon startup while the car was still in park. The fan belt has its own tensioner and does not require adjustment. It may require replacement from time to time, but as a practical matter, this hardly ever happens -- my '94 BMW still has the original tensioner, I have a '97 Ford with the original tensioner, and I had a '95 Ford with the original tensioner, my daughter has an '00 BMW with the original tensioner. I seriously doubt your belt tension is bad. You could have a worn belt, or a worn bearing on one of the pullies that the belt goes around (I'd suspect an idler pulley before any of the pullies on stuff such as the Power Steering Pump or Alternator, etc.)
If your noise is associated with movement of the car, going in Reverse for example, then I'd begin looking at items like the brake system, and the parking brake above any of the others -- especially if you are in a cold weather climate and actually employ the parking brake.

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