PD115 aux belt whine - alternator?

JNH

Registered User
Hi all - recently my PD115 B5 has had a whining emitting from what I assume is a pulley, or tensioner. It has slowly been getting worse (it's more prominent in the cabin and mainly low RPM) to the point where it now sounds supercharged!

The pitch of the noise changes under load (so If I apply rear heated screen, or operate the windows) and I've noticed the voltage will drop to 12 while steering is applied, it feels like extra strain is being applied while steering.

Unrelated but I've been running without an undertray for months - in heavy rain it can make the belt slip and stop charging the alternator briefly. Not sure it's related.

Gut feeling is alternator pulley - it's probably original. Or the tensioner itself. EuroCarParts are doing a full alternator for £51. I know it'd be cheaper to do just the pulley, but for the sake of £50 I'm happy to do the alternator.

Anyone ideas on the whine? Is this usually indicative of a failing pulley? Thank you.
 

midas

Registered User
Is that an RTX alternator? If so, I wouldn’t bother.

mine is making a noise not unlike that, and I’m sure it’s the tensioner pulley. They make a right racket when they get worn out.
 

JNH

Registered User
Yeah - I think it's one of the cheaper brands. It could well be the tensioner pulley, the belt doesn't seem to physically move or skip, I thought that was an indicator that the tensioner was kaput, or am I getting that mixed up. It just seems strange that the voltage seems sporadic occasionally. I'm getting it booked in to my garage, I have no problem changing the tensioner or the pulley but I am poor at fault finding and will likely change the wrong thing.
 

midas

Registered User
Normally, I’ve seen old school mechanics use a solid steel item, sometimes a good solid screwdriver will achieve same effect. Hold it hard against the suspect part, and the noise is amplified up the steel item. Can find items with knackered bearings using this method. Diagnosed the water pump bearings on my missus fiesta. Which incidentally we were told was the a/c compressor pulley. Could have been an expensive error if hadn’t used this method.
 

JNH

Registered User
I had it with my Saab recently - amazingly, I found the exact same noise on a YouTube video, proceeded to change the idler pulley and was met with silence. Utter bliss. Doubt I'll be as lucky again..
 

JNH

Registered User
Noticed my PSF was below minimum today so have topped it up with the green VW rated stuff. Initially, it seemed to completely eradicate the whine but it has returned. Is it possible the rack has run dry and caused some damage?
 

JNH

Registered User
Had my belt off today - the tensioner appears to be completely knackered. It literally flops around at the base (where the sort of flange it sits on is) and moves like 10mm each way! Should they feel solid? I think there's far too much movement.. wonder how much they are :(
 
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