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NOISE FROM ALTERNATOR

P

Paul 944 s2

New member
My 964 C4 has developed a noise, which appears to be coming from the alternator. It is a harsh metallic rattle. Any thoughts or sugestions?

Thanks Paul
 
You need to be sure of where the noise is coming from although if the belt is ok only the fan blower is close enough to give the sort of noise you are describing. The alternator bearings else the alternator drive shaft/shims would seem the logical culprit. Are the belt pulleys ok ie not wobbling etc? Unless you want to take the fan etc apart you should take it to a dealer to have it checked asap.
 
Thanks Alexander, the belts and pulleys seem fine. I have placed a large screwdriver to the outer shroud of the alternator fan housing and can hear the noise here quite loudly. Does the alternator have bearings that are prone to fail and become noisy or could this be something internal within the engine its self?
 
Alex , I had a similar issue and it was the belt hub on the alternator shaft ..not the alternator. Once I had confirmed this, I upgraded to the fixed RS hub so it never happens again .

Take the belt off the alternator hub , and spin the hub and/or the alternator to see/hear the issue . If its that bad you will hear it at low revolutions..alternators aren't cheap even exchange ;-)
 
I started to look at this tonight, and found that a previous owner / mechanic has rung the centre of the alternator shaft - where the splined tool locates. I took the belts off one at a time and discovered the noise to be coming when the outer pulley is rotated. Am I correct in assuming that this is the belt hub of the alternator shaft and can be cured by buying the replacement bearing kit from my local OPC.
I still have the problem of removing the nut securing the pulley to the alternator shaft, but hope a local engineering firm can sort something out regards this.
Thanks Paul

Very relieved that it is the alternator not the engine that was making the noise!
 
Yep the inner one is the hub bearing the out pulley is locked to the alternator.
The hub was approx £80 ...but the better bet in my eyes is the RS hub that locks it all together, this is also approx £80 all in as well. This will solve the possible issue of the belts melting and snapping when the the hub fails and heat damages the belts .....my one did this 1 year after a new hub was fitted to solve the noisy bearing issue. Porsche found this out years ago ..thus the RS one ;-)
 
Thanks for your help. Can you just confirm - I am getting the most noise when rotating the outer pulley (the one nearest the rear of the car) that this will be the bearing and not the alternator. I dont want to order the hub and find out that its not the cure. Sorry to be such a pain, thanks Paul
 
I have the parts ordered, I went for the upgrade to the 993.106.051.80 as both this and the 964 hub were the same price (£84.25 + VAT). Hope to get them for Friday.
 
A little job for the weekend . As to getting the nut off ..your need a spline key ( in the tool kit ) and some brut force ...PS: its a normal thread as well.
 
Yes, my problem is that the splines are no longer there - someone in the past has rounded the centre of the shaft, so there is no way of holding the shaft to unscrew the nut. I was thinking of getting a local engineering firm to weld something such as the head of a splined bolt to the end of the shaft. Would this have an effect on the balance of the alternator or not make much of a diffference?
Paul
 
Ooh nice ....it could be quite tight ..as for the balance depends how big the nut/bolt is but being close to the shaft shouldn't be too much of an issue. The welding heat wont help the temper of the shaft though..it will go soft.
 
Nothing is ever straight forward. I live quite close to an engineering works and hope to go there later this afternoon - they should be able to help. Is this a common thing to happen due to the tightness of the nut / use of the wrong tool?
 
I've heard of them being tight but not messed up . The torque settings of the main alternator nut, should be 50Nm for the standard hub and 40Nm for the RS hub.

Good luck
 
Sorted! The engineering works have Tig welded a small piece of round steel bar onto the end of the alternator shaft that has internal to suit an allen key. They machined the bottom of the bar on the lathe so that it could recess into the hole that was messed up. Just going to take the cooling fan off now and get it cleaned up ready to re assemble when the bearing arrives on Friday.
Paul
 
Glad to see you're making good progress on this [:)] and Ian that write up of yours on Pelican is great. Keep up the good work.
 
Paul, might be worth posting a pic of your improvisation! others with a similar problem can do the same. Glad to here you are getting it sorted.
 
Ian, sorry to be a pain again. I have just come home with my RS hub and am about to fit it. I removed the spacer sleeve at the bottom of the alternator shaft and was suprised that the new hub just slid onto the shaft and can rotate freely on it. Should this be the case, or is something wrong, thanks Paul
 
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