300D Squealin' Like A Pig

During the last week or so I've been noticing a squealing noise occasionally coming from under the hood of my '91 300D 2.5. It sounds like a loose belt, and arises (1) when
I'm braking, and (2) when I'm coasting downhill without the brakes being applied. There's no apparent relationship to steering inputs, so I've ruled out a loose belt on the power steering pump.
The noise seldom, if ever, arises when the engine is under load. And when it happens while the car is idling in drive, applying the brakes will usually cause it to stop. All of this sounds contradictory, which is why I'm puzzled.
Any ideas what the cause might be?
Geoff
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going to do, shoot me?" -- John Fitzgerald Kennedy
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any ware on belt?
abs?
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No discernible wear on the belt, and the belt certainly seems to be tight enough, with 1/4" - 1/2" play in it at the midpoint between pulleys. But you seem to be missing my point, which is: Why would the described conditions cause the belt to squeal in the first place?

Yes, my car has it; no, I don't feel it pulsing when I hear this noise. Remember, sometimes the noise becomes evident when I'm not even braking.
Geoff
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Arabs without the fighting spirit." -- Ann Coulter
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If your car has a belt tensioner I'd look at it rather critically, also its alignment with respect to the other pulleys.
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Are you sure your brake pad is fine?
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Yup -- they were all just replaced about a month ago.
I'm intrugued by T.G.'s suggestion that the belt tensioner might be the culprit. I'll take a gander at it this weekend.
Thanks, all.
Geoff
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I'd double check your brake pads... if you got abnormally wearing rotors, it will wear down fast.
I believe the tensioner is the culprit for squealing... but it doesn't have anything to do with braking.
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The thing is, the rotors, like the pads, are brand new. Well, practically; they're about a month old.
More tellingly is that when I pull into my driveway, the noise often continues even after I've braked to a stop and I'm sitting there immobile with the transmission in Drive and the brakes applied. I've also heard the noise when the car has been idling with the transmission in Park.
Geoff
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60 million Americans pulled the lever for George W. Bush, the
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Try to spray a little water to the belts, if the belts stop making that ignoring noise... you know what to do
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Or go to the local parts store and get a small can of belt dressing and spray the belts. Two dollars. This may be the cheepest fix you have. If this doesn't work, things get more expensive from here.
Larry In the back yard, under the oak .
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Sounds like belts to me, but a sticking caliper could be making for a little trouble - next time it happens try tapping the brakes a couple of times in succession just for the heck of it....
bad pulleys can cause squealing like this - sometimes they get separated, or bent slightly out of alignment - if left unchecked they can tear up an alternator/ps/water pump pretty quick... but usually the belt will show excessive wear on one side.
ts

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