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Join Date: Jul 2007
Location: Honolulu, HI
Posts: 31
Anybody replaced an alternator bearing?

Hey all,

Symptoms: Alternator making noise the last couple of weeks, sounds like metal on metal friction, worse when car is first started and subsides as it runs. Last couple days the alternator has been heating up and smoking when under stress (like long hill climb), appears to be coming from pully area. Battery is charging fine. No belt squeal and belt itself looks to be in good shape.

Diagnosis: My best guess is bad alternator bearing, causing pulley friction leading to hot alternator and smoking.

Question: Anybody ever experienced something like this? Ever changed out an alternator bearing? What kind of job is this and what kind of time committment am I looking at?

Thanks. You guys have helped me out of jam more than a couple times.

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87' 924S Guards Red
Old 01-15-2009, 09:01 PM
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why bother?

In England, one would go to an alternator shop and get a rebuilt unit in exchange for the old one and $40 or $50., complete with a guarantee.
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1986 924S bought new. Now used for AutoX and street.
Chipped, throttle cam, highflow filter in original airbox/snorkel, 14mm rear sway
Hyundai Ioniq hybrid daily driver
Vindicator Vulcan V8 spyder, street legal sports racing car
(300hp,1400 lbs kerb weight) used for sprints on circuits, and hillclimbs
Old 01-16-2009, 01:51 AM
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Let's go shooting.
 
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Ye alternator shoppe, you say? Is the Earth still flat in your part of the world?

Maybe back in ye olde days when there was always a little man in a unit outside the village who could refurbish them for 20 olde pounde notes. That was before old style trading estates were phased out and rebranded as 'Science Parks' and simply concerned themselves with diddling about with paper and PR bollocks.

In the modern world we have to go to somewhere like Porscheshop who will charge about 264.26 for an exchange unit. That's $394.35 in your colonial money
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1983 944 Lux (manual) 2.5 litre 8 valve na and no pas

1991 944 (automatic) 2.7 litre 16 valve na and pas

"I have only five words for you: From my cold, dead hands."

Last edited by Dark Skies; 01-16-2009 at 05:15 AM..
Old 01-16-2009, 05:08 AM
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If you Google your city and "Auto Electric" (exact phrase) you'll find several place that are at least worth a call.

Try this
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'99 996 Arctic silver over black. In the past I've owned and wrenched on a '96 Audi A4, '86 944 NA. '79 928, '72 914. Non-Teutonic vehicles of interest: 3 MGB's (one converted to V8 power), Triumph Stag & TR250, Jensen-Healey, T-Bird SC. Most recent "project" was a Factory Five MKII Roadster.
Old 01-16-2009, 05:29 AM
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I have a couple of functioning used alternators if you need one, PM me for info Replacing the bearing is one of those catch 22 scenarios. If you replace the rear bearing, the front is soon to follow! Not to mention that since the shaft has been spinning off center, it usually damages the rolling contacts inside... Hence why it is better to use it as a core and get a rebuilt unit. Or used...

-Nick
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Old 01-16-2009, 05:55 AM
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You can do it but it needs additional work as many mentioned.
You should get a new VR if your brushes are shorter than 1/4 inch.
Then you need to "dress" or machine the slip rings the VR makes contact with. Do you have a shop lathe handy?
Then front and rear bearings.
After you finish you should take it to a store to have it checked for output....and then find the diodes are bad.

So, If I have not discouraged you enough here is a link to DIY:
http://www.3dzubehor.com/Rover/Boschrepair.html

GL
John_AZ

1988 924S + 1987 924S DD
1979 924 + 1977.5 924 + 1970 914 1.7 + MG Midget +++===gone, past tutors
Old 01-16-2009, 06:30 AM
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Well, you guys have confirmed what I suspected.... no easy way to do it but either buck up for a new one or get this one rebuilt. I'll see if I can find something locally today... unfortunately the Big Island of Hawaii isn't swimming with Porsche parts... appreciate the help.
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87' 924S Guards Red
Old 01-16-2009, 10:04 AM
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do it

just pull the alt apart and replace the bearing if you want to.
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There may be nothing quite as expensive as a cheap Porsche: Ruby Red 84 928S : White 87 924s 2.5L NA (Blinky) M44/07-43H10676 spoiler delete - 046/2B - Belts 9/12, Clutch and OC seals 8/08 andd Red 94 Del Sol: Please put your Make, Model and Year in Sig. Try not to break more than you fix.
Old 01-16-2009, 10:13 AM
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You better do something sooner rather than later. I had one with bad bearings that I kept using because I was sure all the rattling and grinding was the already known to be shot AC compressor clutch bearing. Well, one day far away from home the thing seized up hard and took the belt with it because the bearing got so bad the rotor jammed against the coil core around it. If it gets destroyed to badly, they might not accept it for a core exchange. BTW, A good battery will get you at least an hour of drive time by itself.
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1987 silver 924S made it to 225k mi! Sent to the big garage in the sky
Old 01-16-2009, 05:14 PM
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Im in CT in the good old USA, We have a bunch of shops that will rebuild or trade Alts. For cheaper than new, Infact I got one less than a mile away from my house. They are still there just look around more
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1986 951, Stock for now.
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Old 01-16-2009, 11:56 PM
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Quote:
Originally Posted by Dark Skies View Post
Ye alternator shoppe, you say? Is the Earth still flat in your part of the world?

Maybe back in ye olde days when there was always a little man in a unit outside the village who could refurbish them for 20 olde pounde notes. That was before old style trading estates were phased out and rebranded as 'Science Parks' and simply concerned themselves with diddling about with paper and PR bollocks.

In the modern world we have to go to somewhere like Porscheshop who will charge about 264.26 for an exchange unit. That's $394.35 in your colonial money
LOL - "diddling abouty on PR bollocks"........."colonial money". I love heavy Brit slang - you guys aren't still upset about the 1700's, are you?

Anyways, I'd just remove the alternator and go down to the local Pep Boys or whatever and tell them that its off a WV Rabbit. You now would like a rebuilt one, please. Fortunately, these alternators are pretty common Bosch units. Thought I needed one as well years ago and found all of this out myself.
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1987 944S
1984 944 (R.I.P.)
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2003 BMW 325xi
Old 01-18-2009, 05:52 PM
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Interchange?

DO I smell an interchange? could it be that out illustrious pedigreed 944's actually share an alternator with the common VW Rabbit? Tell me it isn't so! Why I was just aghast to learn that the O2 sensors were the same as a Ford Taurus. Then to learn the ignitition switch is the same a s a VW bug?. Why this is just scandalous!

Seriously though folks, keep those interchange items coming.
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There may be nothing quite as expensive as a cheap Porsche: Ruby Red 84 928S : White 87 924s 2.5L NA (Blinky) M44/07-43H10676 spoiler delete - 046/2B - Belts 9/12, Clutch and OC seals 8/08 andd Red 94 Del Sol: Please put your Make, Model and Year in Sig. Try not to break more than you fix.
Old 01-18-2009, 09:33 PM
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Let's go shooting.
 
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Quote:
Originally Posted by Panzer909 View Post
...you guys aren't still upset about the 1700's, are you?
Not at all. I married an American so every time we pop over to Ohio to see the folks I take back a few handfulls of dirt in some tins. If Strongsville, Youngstown and Medina look a little smaller than you remember it ... chalk that down to me. Stealing America back one tin at a time.

Good tip on the VW Rabbit crossover.

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1983 944 Lux (manual) 2.5 litre 8 valve na and no pas

1991 944 (automatic) 2.7 litre 16 valve na and pas

"I have only five words for you: From my cold, dead hands."

Last edited by Dark Skies; 01-19-2009 at 04:58 AM..
Old 01-19-2009, 04:56 AM
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