Alternator noise revisited
 

Sorry to belabor the issue, but if there is a 'grinding' noise at low RPMS from the alternator area, what would be grinding?
I don't see the fan rubbing against the housing, and although the fan belt isn't real tight, I don't seem to be able to move the fan (so I don't see any play).

Do the bearnings 'grind' as they turn when they begin to wear out?

Remove the belt momentarily and see if the noise goes away. Bearing noise is usually the first sign of mechanical failure on the alt.

so you checked that the fan wasn't rubbing the fan shroud. It may be hard to see. Alt bearing noise is different from the fan rubbing noise. maybe remove the belt and check alt bearing play?

the pully hub may be beat?

see...the guy at TRE (where I took my car to pass smog and had em adjust the valves which really made a huge difference in the car by the way) said the fan was probably rubbing a bit..but I figured "how..." but ronin you could be right. As the first guy said, I'm gonna have to pull it and run it for a few and see if it goes away, which is the plan...

so the noise stops.. so you gotta find the rubbing.

You might get a good feel where it may be rubbing by hand turning the fan?

also sometimes the previous alternator install leaves the fan mis-aligned and bearing wear eventually caused fan rub.

If the fan hub is beat it can usually be patched up or you will need a new fan. If everything is tight and you can't see or feel rubbing I might consider examining the fan hub. It'll be the end of the somewhat rectangular hub fitting that gets rounded. It's a long shot but worthy of a note.

Great advice...I had a devil of a time getting new alternator installed. Installed it wrong and all this stuff..was not fun (but it looked so easy)....it took a year for it to start rubbing....and it's gotten progressively more noticeable. Okay, I'll try those out and post the results thanks!

Intersting..I've been trying to track down a noise that is not grinding or scraping..more like a hollow tone. I think I read somewhere that the plastic shroud on some cars resonate. Anyone else experience this and have a cure??

If you don't get the 6 small bolts on the back of the alternator tourqued evenly, it can get the whole assembly cocked in the shroud enough for the fan to rub...

Cstreit:

So what is the tourque value for those bolts?

Jim

I'm not hearing a rub and I'm not seeing evidence of rubbing on the fan housing. What I hear sounds like a hollow plastic or cardboard tube..something like the tone you get when you blow into a large soda bottle or a jug...you guys remember jug bands.

The top of my motor had that hollow sound too. Once I removed the fan belt and ran the motor for a moment, it was obvious the alt/fan was the noisemaker.

When I spun my fan by hand with the belt removed, it was apparent the bearings were bad. There was a clicking type sound. Be sure to spin the fan only in the normal direction to get an accurate sound and not break brushes. There won't be load on the bearings without the belt, so any noise you hear is probably a bad noise that would only be magnified under load.

Pulley alignment, belt tension and condition are other things to look at along with possible contact by the fan inside the housing.

Yep, remove the belt and run the engine very very briefly. Spin the alternator by hand. It should be smooth as butter. Anything less means a bad bearing. When under load and spinning at regular speeds, worn bearings rumble and growl. Alernator bearings usually make more of a rumbling sound, and wheel bearings growl more, but it's really the same noise. Also, you can use a stick or long screwdriver against your ear and against a part to listen to what's going on with that part. Unfortunately, the alternator is not accessible but the fan shroud is, and the alternator is bolted to that. Put your hair in a pony tail, don't wear loose clothing and be very careful. Or better yet, shave your head and work on your car in the nude.

LOL

Very true on the safety issues (you what is really bad..hooded sweatshirts with those damn dangling strings)
Anyway, in my case I have a new alternator with 3K on it and the new engine. I doubt its the bearings. The pulley alignment looks right on? I read in UP fixin' years ago that some housings did resonate.

If it's rebuilt replacement unit, don't bet on it. I have an alternator(rebuilt/exchange) with less than 5K miles on it. Guess what?! Bad bearings....I hate replacing alternators on these cars. :mad:

I have to laugh. During my rebuild my mechanic asked me..what do you want to do with the starter and alternator since they are both 27years old? Yeah, well I guess I should replace them both as long as we are in there. So I bought a new alt and a rebuilt starter..even though my old parts never gave me troubles. The starter hasn't fully engaged 3 or 4 times and I'm praying the you are wrong about the alt. Although now that I think about it I have always had this noise back there. So it might be some sort of odd ball resonance. Occurs between 2 and 3K.

Wow. It appears as though this was caused by using the wrong fan belt of all things. I had a Porsche one handy, and I compared it to the one I had on there I had gotten some place.

Noticed I guess, that these are completely different. Porsche is thicker, not ribbed and actually shorter.

After taking fan/alternator out yesterday, I was at a loss as to what could be going wrong there.

For the hell of it, I put the Porsche one on. And then I remembered how hard it was to get a new Porsche fan belt on (in comparison to the other one I had).
Got it on there, torqued it. And the grinding is completely gone.

I should say, the other one was looseish, even though I had it about as tight as it would go. I guess the other one worked for a few months before it became useless. Usually when belts go bad in my experience they squeal if they're the right length to begin with. This one, when it got old simply stretched way out of spec while otherwise being in fairly good shape. Gotta chalk this up as another bozo experience. Wish I had tried this 4 months ago.

Not ribbed....do you mean ribbed on the inside circumference of the belt? Ooooh, boy, mine is ribbed internally too, if that is the case.

Well, a pic is worth many words so here's the one I took off versus the Porsche one installed.
It is not just a matter of shadow. There no ribbing on the interior circumference of the Porsche belt.
http://forums.pelicanparts.com/uploa...1117489823.jpg

I have a low, kinda hollow rumble noise that does not change with the RPM's. My mechanic said I had 2 months left on the alternator. I took the alternator to a rebuild shop, sounded fine on the bench. Told him to rebuild it anyway.
Back in the car, smooth as butter. Same noise. Next time I was by the mechanic, I ask about the noise, he thinks it's still the alternator. It's not.
The shroud is tight and doesn't vibrate. I would like to know what it is. I kinda forgot about it untill I saw this thread. ????

Kurt:
Same deal for me. I didn't think the alternator could make so much noise.

Pat

http://forums.pelicanparts.com/porsche-911-technical-forum/222945-noise-over-bumps.html

Well, here's the deal. I put the Porsche belt on this afternoon and drove it. I can no longer hear any of the noise back there at idle. I can't hear it at all in fact.
There is some play in the alternator bears or in how the fan is mounted, and a belt that could not be tightened properly was definitely the wrong combo. The noise may return...but as far as right this moment, the fan is not rubbing at all. I took the fan off and swung it. There was definitely something w/ the wrong fan belt at work there. Keeping mind, there was no way to get it the right adjustment, and those ribs weren't makin' it.

I'll post if it returns some weeks or months from now, but so far it looks good!

it's a good thread without a conclusion. All your fans want to hear a nice ending.. like me.

Be on the lookout for a butterscotch 911 with a leaf blower duct taped to the decklid on 12 June.

I am hoping for Divine Intervention with some Sport trans mounts and alternator bearings in the next ten days. The alternator noise is under control for now, but I suppose it's been there for a while, I just didn't notice it. My car was relatively quiet until this beer bottle episode started.

Also, at the risk of any blasphemy, it seems that the car is a bit more squirrely with those WEVO engine and trans mounts. I'm kind of hoping to get some other opinions out on LI.

Kurt B and my alternators may be getting last rites this summer.

Pat

anytime I do anything in the mount direction I align the engine's long cross mount from the bushings to engine. The engine is operating with the 4 bolt nut's not night at all. I'll rev it a few times and try to make sure it settles in. It helps prevent unwanted harmonics.

Ron:
That's what I was going to try, maybe get everything loosend up to snug, realign the carrier to engine bolts, and try to gradually torque everything down from there. It may have picked up a preload from years of running with broken rubber mounts.

Hayden at WEVO suggested something similar to this and what you said. He also said to go to the Sport mounts on the trans if this doesn't help.

Pat

I just let it low idle after reving it then shut down. I tighten all nuts snug then go again to tighten.

may the low harmonics god be with you

Mine was doing the same and I had hoped it would go this way (Altn. bearings ) but
no noise this AM /checked with Stetho-scope no noise coming from shroud area /BUT lot's of noise from base area near Distributor / which is also Quite warm to touch.
Tensioners / rails and sprockett replaced 4X yrs ago (driver side)
? what do you think..
car 83 SC 160k's
Rika