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Thu Nov 20, 2008 11:14 am

Took my bug out last night for the first time since putting the motor back in and noticed a noise coming from my alternator. It seems to be coming from around the pulley side but the pulley isn't rubbing. It's kind of a scraping, rattling noise. I checked the fan and the bolt is tight and it doesn't scrape. The belt was a little tight so I pulled it off and started it up, no noise so it's definitely coming from the alternator/fan. I also spun the alternator with no belt on it and I can't hear the noise, it spins freely and there is no play in the shaft. When I had the engine apart, I also pulled the shroud apart to paint it and the alt backing plate. I put all of the spacers back in just like they came out. I'm assuming a bearing is going bad in the alternator. What do you guys think? Has anyone had experience replacing these bearings? Any tips? This is a Bosch alternator and I've had a Motorola apart before, they look very similar so I don't think I'll have trouble with this.

Thu Nov 20, 2008 11:22 am

You can get that noise from a cracked fan center hub - where the big nut clamps it onto the shaft. I chased that kind of noise for months till I discovered the crack. Replaced the fan, and counted my blessings that it hadn't failed completely and left me stranded.

Thu Nov 20, 2008 11:26 am

I have got the belt to tight and got some strange noises

Thu Nov 20, 2008 11:31 am

Yeah JeffT, I did that once too. When you rev up you can see the alt pulley flex and cuts a groove in the arms. I go with a loose belt setting now. No more problems from that.

Thu Nov 20, 2008 1:07 pm

ed stanley wrote: You can get that noise from a cracked fan center hub - where the big nut clamps it onto the shaft. I chased that kind of noise for months till I discovered the crack. Replaced the fan, and counted my blessings that it hadn't failed completely and left me stranded.

I will check that tonight and loosen the belt up more. Thanks for the help guys!

Thu Nov 20, 2008 7:10 pm

Do you have the strap that goes around the alternater and the stand?

Mon Nov 24, 2008 7:10 am

Endicott jb wrote: Do you have the strap that goes around the alternater and the stand?

Yes the strap is installed.

I pulled it yesterday and there are no cracks in the fan. I'll re-install it tonight and loosen the belt more. I'll let you know what I come up with.

Mon Nov 24, 2008 9:43 pm

I put it back together and put the belt on loose. I've got about an inch of belt deflection. The noise is definitely quieter. Maybe this will let it last for a while longer. Thanks for the help guys!

Mon Nov 24, 2008 9:58 pm

just a thought, once i forgot the spacer behind the pulley. the pulley was rubbing on the face of alternator. if you pull your pulley off you will be able to see were it is rubbing. this seems to happen more with aftermarket pulleys.

Mon Nov 24, 2008 10:18 pm

pafree wrote: just a thought, once i forgot the spacer behind the pulley. the pulley was rubbing on the face of alternator. if you pull your pulley off you will be able to see were it is rubbing. this seems to happen more with aftermarket pulleys.

Nope, pulley's not rubbin'. The fan has all of the spacers in it too. With a piece of vacuum tubing I was able to isolate it to somewhere inside the alternator. There are brushes in an AL78, right? :?: I'll have to check that out tomorrow.