Alternator Rattle

Superman · 02-21-2003, 11:41 AM

I'm getting tired of a low rattle or rumble in the fan housing area. I've been assuming it is a rear alternator bearing. It is not a whine or a growl. More of a rumble or rattle. Does this sound like a rear alternator bearing? If I remove the belt, should I be able to detect play in the shaft?

Pillow · 02-21-2003, 11:45 AM

Speaking from a VW perspective I have seen this happen when the shaft bearings are almost ready to go south. THe last one that was whining on me eventually ate the bearings.

I think if you can feel some play or detect some resistence if you took off the fan belt.

Good Luck,

Al S · 02-21-2003, 11:55 AM

If the rumble is only at idle, and you can see the drive belt vibrating significantly on the slack side, then the belt is making the noise. There was a previous thread on this a while back.

Superman · 02-21-2003, 01:10 PM

Yes, my belt is indeed loose. Thanks.

89911 · 02-21-2003, 03:40 PM

My exchanged rebuilt one does the same. I can reproduce the rattle by grabbing the fan blade and moving is back and forth with some effort. Most likely worn bearings and perhaps the fan belt is too snug.

911cab_84 · 08-23-2003, 02:17 AM

I too am having the low rattle at idle only coming from the fan housing area. I can see the fan belt vibrating more than it should at idle only, and it sounds like it is the belt making the noise. When at 1500 + rpm the belt stabilizes and the noise seems to cease (hard to tell over high rpms).

Will moving one shim outside be enough to prevent belt vibration, while not being too tight to damage alternator bearings?

Just looking for some info from people who have experienced this, having never messed with the shims/belt before. Thanks.

ruf-porsche · ruf-porsche's Garage

Moving one shim will tighten up a loose belt. I just replace all the belts to my car after the ac belt broke. I adeded a shim to the fan belt pulley so that the fan fan belt will not be too tight.

RoninLB · 08-23-2003, 06:21 AM

Quote:

Originally posted by 911cab_84

Will moving one shim outside be enough to prevent belt vibration, while not being too tight to damage alternator bearings?

the routine is to push in the belt at idle and somewhat measure the deflexion.. what I do is manually give the throttle a quick blast to see how the belt handles it. if the downside of the belt vibrates noticably I'll pull a shim. a new belt should be re-checked after a 100 miles, then 500 miles till it's broken in.. a bearing could be overloaded if overtightened. and a winter lay-up could produce a bearing flat spot that would become a problem in a few hundred miles. the belt width is another consideration if it's 10mm.

Superman · 08-24-2003, 12:00 AM

Another thing that can cause the rattle is, if the correct total number of shims are not in there, then the nut will not completely tighten against the dished washer. The washer will eventually wear crooked, too. I replaced my washer and added a shim or two, and the noise went away.

911cab_84 · 08-24-2003, 12:05 AM

Ronin LB,

The belt vibrates at idle only. When I throttle up, the belt seems fine.

How much play is a 'normal' belt supposed to have in it?

I'm going to tighten it tomorrow, i'm just worried about over tightening. I'll try one shim first.

Superman · 08-24-2003, 01:18 AM

Who knows the correct number if shims? Again, without the correct total number

(shims between pulley halves) + (shims under cup washer)

then the assembly will rattle. Not sure what the correct number is, but it's important.

Superman · 08-24-2003, 01:18 AM

Who knows the correct number of shims? Again, without the correct total number

(shims between pulley halves) + (shims under cup washer)

then the assembly will rattle. Not sure what the correct number is, but it's important.

Superman · 08-24-2003, 01:18 AM

Who knows the correct number of shims? Again, without the correct total number

(shims between pulley halves) + (shims under cup washer)

then the assembly will rattle. Not sure what the correct number is, but it's important.

bell · bell's Garage

1.........2........3........you win superman LOL

the correct number of shims is 6 total on my 3.2.......

sleeping_beast · 04:35 PM

Hi,

I too hear rattle in the fan/alternator housing. Recently, I was driving and the alternator warning light began to glow. I thought this was simply a case of loose alternator belt. However, I changed the belt and adjusted the tension... I still get that rattle in the fan/alternator housing and my alternator warning light is constantly on.

I removed the belt and was very surprised to be able to move the fan shaft for at least 1/16" from left to right or down to up. No axial movement though. When I manually turn the fan, I see the fan rubbing the housing.

Is this a case of alternator bearing replacement?

Thanks,

Alain

p.s. I only had 5 shims (2 inside, 3 outside)... Wayne specifies 6 shims in his book... any problems with one missing?

RoninLB · 08-26-2003, 03:28 AM

Quote:

Originally posted by sleeping_beast
[B
Is this a case of alternator bearing replacement?

[/B]

or fan replacement

arringto · 09-07-2003, 08:44 PM

6 shims . . . Always supposed to use 6 shims. .

Arringto
68 911 Targa (2.4 t)

sleeping_beast · 09-08-2003, 08:08 AM

Hi,

I removed the alternator during the last weekend. It really looks like the bearings are worn out. Moreover, small pieces of metal fell from the alternator so I guess I'm in for a complete alternator rebuild. By the way, I lost one of the two lateral bolts that hold the fan housing to the engine... What type of bolt should I buy to replace it? That's probably a 10 mm one but are there a variety of threads for these metric bolts?

I had some problems to remove the alternator from the fan housing. I could remove it with WD-40 and light tapping on the studs. I screwed up with the fan though. I just couldn't remove it. I even damaged the threads of the alternator shaft and can no longer thread in the nut.

What's the usual way to remove the fan?

Man... the engine case is SOOOO dirty behind the alternator... There is a thick layer of greasy black stuff. Can this layer interferer with engine cooling? Should I clean that?

Thanks,

Alain

Gunter · Gunter's Garage

Yes, you need to clean the Cylinder fins for cooling. Check Tech articles on Alternators on this board.

targa80 · targa80's Garage

If you are a DIY'er and you need to replace the bearings. Just take the part number off of the side of the bearings and call up a bearing supply house from the local phone book. Thats what I did when I needed to replace the bearings.