Rattling noise coming from Alternator

**macmillions** · 20-01-2010,07:40 PM

Normally on my '90 GL, eveything runs very quietly for a 20 year old car, however, recently it has developed a strange clattering noise from the alternator... Not overly loud, but certainly noticeable over normal engine noise.

I looked to see if the cooling fan on the alternator was clipping the support arm or the cambelt cover, but it seems to be clearing them both by at least a couple of mm.

The belts seem as tight as they should (depress a cm or so when pushed by my finger).

Any idea what this is likely to be? And if I should get it sorted asap?

The alternator is charging the battery as normal, so is still doing what it should do.

**zollaf** · 20-01-2010,08:03 PM

sounds to me like the bearings are shot. try a squirt of oil onto both ends, aiming for the bearings to see if that helps.

**macmillions** · 20-01-2010,08:12 PM

Ok, thanks for that quick response. What type of oil should I use? Or just WD-40?

**zollaf** · 20-01-2010,08:15 PM

wd40 would be good. i think the bearing has possibly gone dry, so any oil is better than no oil. if it does shut it up, then give it a squirt every now and then to eek a bit longer life out of it. eventually you will have to either replace the complete alternator, or rebuil it with new bearings, available from a bearing supplier for a few quid. just take the old ones in to match them up.

**macmillions** · 20-01-2010,08:20 PM

I shall get on it and see if that helps at all.

Are the bearings something even a mechanical novice, such as myself, could tackle? Bearing in mind that I was pretty pleased with myself when I changed a wheel haha.

**zollaf** · 20-01-2010,08:23 PM

probably not in that case, but there are people that can. you just dismantle it, pop the bearing out, new ones in, bolt back together. ask in your local motor factors if they know anyone locally that can do it. probably a lot cheaper than an exchange one.

**macmillions** · 20-01-2010,08:31 PM

I thought that would likely be the case.

I actually work for an aviation company that refurbs aircraft generators (I work on the control unit, so don't deal with the generators themselves), so I may ask one of my workmates if they can sort it for me... as an alternator is basically a generator am I right?

**zollaf** · 20-01-2010,11:07 PM

indeed it is just a small generator. you just take the pulley off then undo the bolts holding the case together. pull it apart and voila. before you do that though, loosen the alt drive belt off and remove it so you can spin it over by hand, and start the engine, just to confirm it is that causing the noise.

**AndySil** · 20-02-2010,12:10 PM

Hello, How you doin'?
This is a real coincidence as I'm getting exactly the same symptoms on my MK2 Golf with what appears to be a noisy Alternator or Water pump. It was suggested by my local garage man that it could be brushes, but like yours, the Alternator is charging fine. Sometimes it's noisier than others. I do have another spare old Alternator that I have just fitted with new brushes, so I could swap them over. Just waiting for the weather to get a little warmer before I start poking about out there!
How have you been getting on with yours?
Cheers,
Andy

**dadrathers** · 21-02-2010,06:50 PM

Certainly could be the alternator but could also be the water pump. Such rattling noises are very difficult to pinpoint. Unless money is a real issue I would change the whole unit with one from GSF or Euro car parts. Much simpler than faffing about with taking the alternator apart.

Best thing to do is pull the belts off and see whether there is any play in the water pump or alternator pulley. They should spin freely without making grinding noises. Doing that you are more liikely to find which one is making the noise.

Good luck.