Tip & How-To about Cars & Trucks

Squealing Drive belts

P { margin-bottom: 0.25cm; line-height: 120%; } The belts make a squealing noise
'My car made a squealing noise from the belt. I changed the belt but the squealing noise is still there'

This is another very common complaint on Fixya. A new belt should stop the squealing noise? Yes, probably - if it is actually the belt at fault.

There's many different types of belt or serpentine, and many different combinations and layouts. Your car may have just one belt that drives everything - the power steering, the ac, alternator .. or it may have as many as three separate belts running on the pulleys.

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Simple alternator drive belt. Moving the alternator away from the block tensions the belt


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Idler/tensioner on longer serpentine belt. Yes, they need replacing too

To begin with, check your belts. If any of them are cracked and look like the photo below you should change it/them before trouble strikes. A snapped timing belt can cause the pistons to hit the valves. That just means your engine is liable to be wrecked beyond economical repair.
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Cracked and split. When it snaps the results will be disastrous
Your belt doesn't appear to be cracked? Well maybe it has just worn smooth and shiny. A worn, smooth belt can slip and cause that squealing noise.

The other thing to be aware of when fitting new belts is that there is a huge difference in quality between those supplied by the manufacturer or a recognised manufacturer of replacement parts, and dirt-cheap Asian imports. Always go for the manufacturer's parts or quality parts. Asian manufactured parts just aren't up to the mark. Don't buy them.

Okay. So you've fitted a genuine quality belt(s) to your car and the squealing noise is still there.

There's other things that can cause the screeching/squealing. Belts have tensioners. The tensioner may be nothing more than moving the alternator to 'tighten' that particular belt, or it may be a self adjusting or manual tensioner - a small wheel that takes up the slack in the belt. Tensioners wear and fail.
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The tensioner is to the right of the bottom pulley
-it takes up the slack in the belt. The pulleys can wear


Many manufacturers recommend changing the tensioner when that particular belt is changed. Some manufacturers such as BMW recommend changing the water pump too. That's because the bearings in the water pump, under tension from the belt wear out quickly.
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IDL means 'idler' - a type of tensioner

The pulleys have grooves in where the belts fit. Yes, metal pulleys wear. The 'V' in the pulley becomes worn and allows the belt to slip against the sides - hence the squealing noise.

A quick check is to start your engine and pour a few drops of water onto the bottom pulley. If the squealing noise disappears you know the bottom pulley has worn grooves, assuming the belt is okay.

Don't forget the idler/tensioner. They wear out too!

Below: Toothed and smooth belt. When checking any belt, don't look at the outside - inspect the inside. Cracked or shiny? Replace it. Also check the pulley and idler/tensioner



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1 Answer

chevy uplander makes squealing noise under hood


Loose or worn belt. Possibly belt tensioner bad, but unlikely. Change or tighten belt if possible.

Jan 19, 2013 | 2007 Chevrolet Uplander

1 Answer

My 92 chevy blazer is making a loud squealing noise sounds like my belts but its not that I've replaced the belt and the tensioner what else could it be?


Bearings in Alternator, water pump, power steering pump or even a squeal from Vacuum line, EGR diaphram or similar. Check power steering fluid level.



Now when you replaced the tensioner, did you notice more pulleys that were just "there" and not connected to anything? These are idler pulleys and are helpful in routing the belt. They have bearings too!

Pleae rate my info.

Nov 15, 2012 | Cars & Trucks

1 Answer

Squealing noise (LOUD)


You need to check the pulley alignment of all the pulleys, they should all be in a perfectly straight line, otherwise the belt will squeal

Aug 24, 2017 | 1988 Jaguar XJ6

3 Answers

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No, The fan clutch will not make a Noise it will just not catch the Fan to Cool. It is the Belt. Make sure that it is Tight. You may have a Bad Belt Tensioner if it is not.

Jan 23, 2009 | 2004 Chevrolet TrailBlazer

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