Don't lift

With engine running, rear lid open, the noise is quite loud coming from the center of the engine area....seems to be from the fan area. Its like metal hitting metal type vibration sound continuesly, PLUS a louder non-consistent metal clunking or clanking noise. Upon a quick visual check on fan and the general area seems normal and car is running flawlessly Anyone can shed some light on this is truely appreciated.
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'97 Blk/Blk C2S

StevoUK

My gut feel is this...

Dont run the engine.

Visually Check fan pulley, alternator, for loose nuts. Check belt tightness.

Get a motor engineer if its not obvious. The cost of a quick check by someone who knows will save you wrecking something really really expensive.

Good luck!

4X4SCHE

It may be the fan bearing. Push and pull on the fan blades, over 1/16" of play is excessive.

Flying Finn

I'm also guessing fan bearing but please concider all these are guesses based by your description so they mean next to nothing. You need to get someone to listen it.

chris walrod

If you can, remove the belts and start her up (only for 30 seconds or so, no longer), you should be able to tell if its your fan or alternator bearing(s)..

Let us know what happens..

Don't lift

Spoke to my mechanic and he also thinks it is either the fan hub bearing or the alternator is going......he explained the non-consistent clunking and clanking noise is very likely from the fan touching the housing. He told me to look at the bottom of the fan housing right at 6:00 o'clock for scrape marks which I'll do when I get home tonight.
The price of a new alternator is around $1150 compare to $280 for a rebuilt one....anybody have good or bad experience on the rebuilt units?
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'97 Blk/Blk C2S

Luis A.

I recall some posts stating that Autozone had the exact alternator our cars need. Do a search on "Autozone" and "alternator" and see if you can locate it.

dale_loch

Don't Lift,
This indeed is a serious issue that you need to look into immediately. Your fan & the fan housing (shroud) are both made of magnesium. When the fan bearing goes bad your fan blades will begin to scrape the shroud as it is out of alignment. This makes the fan blades smaller as they tear into the shroud. You will see scoring on the bottom of your shroud where the blades are contacting it (the pulley pulls the fan downwards; towards the crankshaft). Magnesium is a metal that needs to be coated and (pray it doesn't catch on fire!). You will need to remove your entire assembly to fix the problem. I would recommend a new fan if the bearing is bad. You don't need to replace your alternator if it is the fan bearing. Someone on this board was selling a new bearing a few months ago. This is also an excellent opportunity to paint your fan and housing!
<garychios@hotmail.com> was selling the fan bearing.


Dale

Rick Lee

I can't understand why anyone would pay those insulting dealer prices for a new alternator. I'd feel less robbed if they used a gun on me. You could go through four or five rebuilt units before you spent as much as a new one costs. Rebuilds are fine. You'll have to remove your whole fan assembly anyway if you're replacing the alternator. If your fan is scraping a little bit, it's not big deal as long as you catch it soon enough. A bad bearing or too tight belt can cause this, but a new alt. and belt will make it right. I can't even imagine how ridiculous the prices on new fans and housings are. They ain't cheap for 3.2 Carreras, so 993's must be astronomical. R&R is not too bad a job, less than an afternoon.

viperbob

Rebuilt alternators are fine. Also, $280 is the list price for a rebuilt. You should be able to get it in the low $200s....

Don't lift

Thanks to all the info and advices.............even a pic to boot ( thanx Dale! )
Took a better look this morning at the fan shroud, sure enough there are fresh scrape marks on the bottom around 6-7 o'clock area. I guess replacing the fan hub is a bit better for the wallet than the alternator.
I don't remember ever had to replace this bearing in my previous 911s with over 250K miles on the clock! Now I'm wondering why this fan hub/bearing went bad at 68K miles? Anyone had to replace it yet? I did have my belts replaced about 2K miles ago...... maybe they did have it too tight? (Rick) How do you gauge how tight is right? By pushing down on it and see if it has some movement?
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'97 Blk/Blk C2S

Rick Lee

Dude, a new fan housing will cost FAR more than a rebuilt alternator. The fan housing did not cause the problem and is not exacerbating it. Leave it as is. The scrape marks aren't a problem; they are an indication of another problem. You have a bad alt. bearing. It either wore out prematurely or the belt was overtightened and wore it out. I don't know the belt specs. on 993's (yet). Find out what it is before you do this job and check it after it's been broken in. I don't even want to think about what a 993 fan housing costs.

4X4SCHE

Older 911's don't have a separate fan bearing or belt or pulley. The fan is on the alternator shaft. The RS upgrade puts the 993 back to the older setup.

John

dale_loch

Don't Lift,
I had to buy a new bearing and hub as mine went out a few months ago (hence the picture). Definitely make the effort and paint your fan and housing while you replace the bearings. See my avatar or do a search (in the archives) and see Sachin's painted fan. You absolutely must have some sort of coating or paint on your fan and housing after the contact (don't leave raw magnesium exposed to the air). I wouldn't worry about replacing the fan right now as it appears that you spotted this problem soon enough. I left the e-mail address of the guy that was selling the new bearing in my previous post.

Good luck,

Dale

Don't lift

Here is the final outcome........the fan hub bearing was so badly worned it scored and put grooves on the alternator shaft. Had to replace both the fan hub and the alternator plus couple of pulley sleeves. I'm considering myself lucky that the magnesium fan and shroud survived! $$$
The mechanic saids they are seeing more and more of this fan hub bearing going bad on medium to higher mileage cars. So, a word of advice.........check for play in your fan periodically and if you catch it early enough you just might have save yourself to replace the alternator prematurely.

My wallet is a bit lighter and I hope this thread is informative to someone on this board.
Cheers! On the road again!
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'97 Blk/Blk C2S