Alternator/Bearing Gone?

[usafa]

I recently got the beast (88 911 turbo) back together and have driven it about 200 miles when yesterday I noticed a fleeting burning rubber smell and soon after, the car died when slowing (clutch disengaged) for a stop light. Note the clutch is a Sachs w/spring centered pressure plate. She started right up, but didn't want to idle, so I drove her home having to keep the foot in the gas to keep from dying at stop lights. I had noticed just prior to driving her that afternoon that the fan had been just barely scraping (just enough to take the top powder coat off) the bottom of the shroud. I figured that was the intermittant low squeeking (chirping) sound I had noticed a few days before.

So is this an indication the alternator and/or bearing has gone bad? Or is this just another CIS mystery? I can hear what I think is the frequency valve kicking in when the idle drops to almost nothing. While driving, there is no appreciable or unusual noise.

A little history. The alternator was replaced with new about 12K miles ago by the PO. I recently had major service done at a "reputable" shop which included new belts. The last bit of work I did myself did not touch the fan belt. Upon inspection, the belt appears new, however, much much tighter than the way it was prior to service. Is it possible the fan belt is too tight?

Anyone with a suggestion is welcome to comment.

Thanks

[john walker's workshop]

too tight can wear the bearings, or if they're already loose, make the fan touch the housing like yours does. the housings also are known to crack and distort because of it, so inspect the housing while the alt is out.

[usafa]

John,

Thanks for your reply. So, am I looking at a bearing in the fan or is it in the alternator? If in the alternator, can it be replaced, or does the whole alternator need to be replaced? It seems to be functioning OK otherwise. I have noticed a crack in one of the vanes on the fan shroud (housing). At first, I thought it was just the powder coating bubbling, but upon closer inspection, it definitely is cracked and slightly deformed.

So do you think the 1K miles or so I put on the car with the belt tight could have damaged the alternator bearing? The belt was visibly much looser prior to belt replacement. And if not, shouldn't the alternator last much longer than 12K miles?

This alternator bearing issue seems to be separate from my idle issue, correct me if I'm wrong. Or could it be that with fan and AC belts too tight and alternator bearing going bad, this is causing a drag on the engine at normal idle speeds and not an issue with the CIS?

[Early_S_Man]

Brad,

Yes, both bearings are in the alternator, and they can be replaced. Any motor/generator shop should be able to do the replacement.

[john walker's workshop]

see if you can rock the fan side to side, up and down. with the belt off would be better. if there's no discernable movement, and it's quiet when you spin it fast by hand, i would suspect that the housing is the culprit, especially since it's got a crack. try adding one or two shims between the pulley halves to slack the belt a bit. 1000 miles with a real tight belt could indeed damage the bearings, but without checking the tension personally, it may well be correct, and it was too loose before.

[Superman]

A crack in one of the vanes would weaken the housing, which is supposed to hold the alternator firmly so that the fan blades don't get too close to the housing. I wouldn't be surprized if the broken housing is the main problem, rather than the alternator bearings. Take the belt off and spin the alternator.

[usafa]

Guys, thanks for the advise.

Sorry I haven't gotten back to you sooner. Been a little busy. Got laid off today and have been a little pre-occupied with that business. Hey, maybe I'll be able to pursue that start-up business now.

Whatever it takes to keep the p-car.