Belt 'chirp' with aluminium pulleys

Leeum

Leeum

Leeum

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19 Sep 2005
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Got a bit of an ongoing issue with some aluminium crank and alternator pulleys I have fitted to my Saxo VTS.

To cut a long story short: the belt makes a chirping noise at idle once warmed up, and disappears when you put some revs on the engine. Misting the belt with water stops the squeaking temporarily - it returns when it dries out. Fitting a new belt stops any squeaking until the belt gets wet then dries out. I've tried belt dressing spray and that only keeps the belt quiet for a few weeks.

Pulley alignment and the belt tension is fine. The tensioner and alternator bearings are also ok. The pulleys are made to a very high standard by a well known competition engine builder. I was convinced something was wrong with the original set of pulleys I had, so the supplier kindly sent me a brand new set with a new Goodyear V belt. Fitted those and I didn't hear a peep for around 2-3 months. For the majority of that time, the belt felt quite loose to the touch (obviously stretched as it wore in). Now the squeaking has returned - exactly the same as before. :mad:

The supplier has sold hundreds of kits and doesn't know of anyone else who's had problems with squeaking. I know of one other person who did have problems with squeaking - he fitted a smaller belt (the one supplied in the kit is a 4PK725) and that apparently solved the problem. I've tried tightening the 4PK725 as much as I can - belt feels too tight imo, and the squeaking is still there.

I'm slightly tempted to try a different brand of V belt. I tried a Gates belt in the past and it kept jumping around on the crank pulley regardless of tension - it didn't want to sit in the pulley for some reason. The only other belts I've tried have been Goodyear.

Any ideas? I am totally stumped. :(
 
I had alloy pulleys on my Xsara VTS-S.

Had no problems with squeeling, but the s/c belt jumped off once. Popped it back on and retensioned it and had no further problems.
 
What are the points of these, other than something shiny to show the other kids in macdonalds car park?
 
Dogbreath said:
How have you checked the alignment...just by eye?
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Can only check by eye, but the lad who produces the kit assures me he spent a lot of time measuring up with a test engine.

iaind said:
What are the points of these...
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The OE crank pulley has rubber a centre and is notorious for splitting from the rest of the pulley. The alloy ones are much cheaper than an OE relacement.

Alternator pulley is slighter larger than normal to preserve alternator life at high revs.

iaind said:
...other than something shiny to show the other kids in macdonalds car park?
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I wonder if that would have been in your post if I said the pulleys were fitted to a BMW 3 series?
 
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Leeum said:
The OE crank pulley has rubber a centre and is notorious for splitting from the rest of the pulley. The alloy ones are much cheaper than an OE relacement.
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That's because, as Clarkey says, it's a harmonic damper. They don't last forever because the rubber takes a pounding absorbing the energy from the torsional vibration in the crank. Manufacturers don't fit them for fun...

Can you get a straight edge (e.g. steel rule) in to check alignment? They don't have to be far out to squeak.
 
Leeum said:
I wonder if that would have been in your post if I said the pulleys were fitted to a BMW 3 series?
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I'm guessing that's as BMW engines are very smooth by design, with (seemingly) little vibration and most having 6 or more cylinders.

With more cylinders and a smoother running engine, the need for a damper is somewhat negated.

No idea why, but I know BMW engines tend to have large flywheels from what I've seen, suppose this could also help.
 
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