Identify this sound...

[Jameel]

My 1983 SC came with this odd sound. Only happens on launch, and only at certain frequencies/rpm. Its definitely related to rpm (disappears when increasing) but also seems to only happen with extra weight on the rear, like when starting off on a slight incline, or when launching on a turn. I seem to think it happens more on left turns, but that could be my imagination. I had a loose muffler strap, but after tightening that its still there. Some of the heat deflector under the cat is a bit loose around the nuts, and the left heat exchanger is a bit rusty where the manifold enters, so those parts may be rattling, but I don't have a way of confirming that. It doesn't make this sound really unless its under some load. I can just barely hear it when revving the engine from a stop, so its not entirely load-dependent.

The rest of the car is solid as a rock. No rattles or squeeks. It's almost like a new car, so this tinny rattle is starting to grate on me. I want to hear my engine on launch, not a rattling can of grandma's button collection.

I strapped my little recorder to the top of the left rear bumper impact pad.

[DRACO A5OG]

Do you have a tail?

BTW, when cold off the line, how high of RPMs do you go?

[Justin@Athens]

Fan bearing is what it sounds like to me. Noises like this are so hard to pin down.

[DRACO A5OG]

To verify, you can remove the belt and take it for a very very quick spin if you can repeat the noise. Do not let it heat up too much, pull over and put the fan belt back on or get home quick to let her cool off. You can't really go far because battery is being drained because alternator would not be charging it. So be close to home.

Keep RPMS below 3500 when cold.

[Jameel]

No tail. I keep it below 3500 until she warms. I recorded this with it warm. I'll do the test with the fan belt tomorrow.

[DRACO A5OG]

Check if engine lid screen is loose, and please do not drive far, maybe 2-3 minutes max???

[gazzerr]

On mine the PO removed the shroud around the cat but left the little metal inserts that capture the nuts for the shroud. These rattle. I spent a bunch of time chasing it. Very tinny.

You can take a soft mallet and tap on the exhaust. That might tell you.

[twistoffat]

Have your chain tensioners been upgraded?

[Jameel]

Okay. Got up early today to tinker before work. This humidity in IA is ridiculous lately. I'm soaked. Anyway, I got the fan belt off. Forgot to mention I have A/C, so spent 30 minutes getting the compressor loose so I could remove the belt.

Deck lid screen/louvers are tight. I have the Carrera tensioners.

Whoever put the last belt on didn't bother lining up the outer shims before cinching down the nut. The outer shims were smooshed pretty good by the washer. I whacked them back to flat with my dead blow mallet and anvil. And there were eight shims total. 4 in, 4 out. I had a fresh Continental German belt in my parts bin, so I put that back on. I put three shims in to begin with, then cranked the engine briefly. Fan was rubbing at the bottom, belt too tight, so added a fourth shim and its quiet now. I'll check it again after a few drives--I'm expecting it will loosen up a bit, then I'll end up with three shims in.

So the test. I drove up the street (half a mile--2500rpm max) and turned onto my little hill to test for the rattle. I inched the car forward up the hill-repeatedly releasing the clutch to see if I could get it to rattle. It didn't. Without the fan I could hear some new sounds, nothing alarming, just stuff that normally gets droned out. I thought I heard a very faint version of the rattle a couple times, but it could have been something else. It was very faint, not the actual rattle. So, sounds like the fan bearing could be the source.

Came back home, put the new belt on and went out for a longer test drive. The first half of the drive I experienced no rattle. I thought it had magically been fixed. But then on the way home, again on the slight incline, it rattled like before. But it's definitely less than it was.

So I think I'll get myself a fan bearing anyway and plan on replacing that. It's the best candidate for a solution at this point. I'm also going to get underneath and bang on some tin to see what I can see.

One other thing looked odd. The crank pulley where it contacts the bottom of the fan housing. Looks like something is a little odd here. It's not rubbing, but looks like it may have at some point.

[86 911 Targa]

Just a thought.

You might want to check the vertical fan housing
clearance to the pulley.

Have a look at the key that holds the fan housing,
and verify that the fan housing is properly located.
It looks like the fan housing needs to move forward,
(towards the front of the car).

I don't see a key in your first picture.

I used 3 & 3 shims on our car.

Good luck,

Gerry

pm me as needed

[gazzerr]

Yes and also it would rub if the bearing is worn out too right?

[DRACO A5OG]

Definitely, fan housing is not seated properly and the noise is coming from scraping of the fan and pulley. When you test drove your pulley was hitting the fan housing.

Loosen the mounting bolts and push it in, the pulley should clear the fan housing lip about 4-5MM

POS or hack wrench put the the shims in wrong and way too many obviously geez

If belt was too tight, then definitely it would scrape the housing, if it still rubs at 3 in, then bearing may be damaged.

[75 911s]

^ What they said and I would buy 6 new shims, a new nut and a new dome washer. I might even buy a new pulley half as it may have been bent by tightening the nut with the shims creating a high spot. They aren't that expensive.

[Jameel]

Thanks for the advice and tips. I got up bright and early today to tear into this thing. Some discoveries...

First up, getting the plastic shroud off the front of the alternator was a royal pain. I'm pretty resilient with fussy work, but this wasn't fun. I'm dreading putting it all back.

And if I refurbush the fan housing, I'm also wondering how I'll get it back in without garfing up the back edge on the engine mount bar. Ugh.

So first off I discovered the wire coming from the engine case stud was not connected to anything. I felt it was loose before taking the plastic shroud off the front of the alternator. This is the ground wire, correct? Where is it supposed to go?



Once I got the wires disconnected I could remove the fan housing/alt. The little boss at the top of the case that keys into recess in the bottom of the fan housing, does this look right? Gerry said "Have a look at the key that holds the fan housing" Is this the key you're referring to? When I loosened the strap I could easily push the housing forward to clear the crank pulley.



With the alt/fan housing out I made a little puller to get the fan out. Came off really easily.



I discovered my fan needs some dental work, it's also worn down where it'd been rubbing on the housing. Do we repair these? Or am I buying a new one?






Checking for cracks in the housing I discovered a spot a raised spot where the fan had been rubbing. There is a also a small crack to the left of the shiny area. When passing a finger over this area there is a noticable hump. Also found another small raised bump that's been getting some contact with the fan. What are my options here? File it smooth, fill the crack/braze?












Before I move forward I still need to get the alternator out of the housing. How do I do this without destroying the alt? I don't see a safe spot to press on here.



Once the alternator is out, I'll check the bearings. But they feel and sound nice as is.

[86 911 Targa]

pm sent.

Gerry

[gazzerr]

I had a shop press mine out but I've read guys using a piece of carpet, a towel and two 4x4's spaced out and on top of the carpet and towel on the floor and gently but firmly thumping the whole thing on to the 4x4's and the alternator will come out and fall on the towel after a few whacks. There was a thread on here about it you search for it.

There's also a guy on here that refurbs the fans and shrouds. You can find him searching also.

The plastic shroud is a pain to put back on but it's just perseverance. I used really small box wrenches and a small ratchet/socket combo. The nuts on the bottom are by feel. Don't tighten too much or the shroud will crack because it's brittle. While the shroud is out you can replace the rivets holding on the metal air diverters if they are loose. Mine we rattling like crazy.

[DRACO A5OG]

Dr Gerry, will guide you in the right direction for all electrical matters

Yes, ground wire and it is already connected to the engine, yours need to be connected to the alternator, again I defer to Dr Gerry.

As far as the fan and shroud, both are magnesium and not easy to work with for even a talented welder. Those casts are very dirty. I recommend leaving them alone, I do not see major fractures just the chip but I think 90% of us have a fin chip here and there. I certainly do.

Once the fan and housing are put in correctly, you should be fine.

BTW, I like your DIY puller

[gazzerr]

Here's the alternator drop removal thread:

Alternator Removal

Someone will know the name of the guy/shop that repairs them. You can also just post a WTB in the parts section. They aren't hard to find.

[Jameel]

Gerry called me. Cleared up a few things, but the jury is still out on where that ground wire goes. I have not looked at Bentley yet. Anyone have a name for someone who does fan housing/fan restoration if I go that route? Right now, since I know my alternator works, and I'm in a three season climate, I'm tempted to just clean and reinstall, then perhaps look into it deeper over the winter.

I am convinced the rattle was the sound of the blades hitting that raised portion on the inside of the housing. It was just far enough away that it only contacted just off idle, if that makes any sense.

[DRACO A5OG]

It should be the bottom terminal but wait for someone with your year to verify.

Take a dremel and shave that nub down, but once everything is seated and proper belt tension it should no longer hit it. After service, reassemble and spin the fan and see.