Alternator bearing noise

FA-18C · 03-29-2022, 05:31 AM

Alternator keeps the battery charged, but compared to previous cars, seems that the bearing noise is louder than others. I have a replacement sitting on the shelf, in preparation, but to the experts, how much play should there be in the fan?

I get a little movement that I am certain is making the noises, but not sure if this is critical right now.

TeeJayHoward · 03-29-2022, 06:46 AM

The only time I've heard noise from my alternator is when there were an incorrect number of shims on the fan belt. It tore apart my fan and pulley.

It wasn't a cheap fix. IMO, it's worth it to take off the belt and check to make sure you aren't having the same problem. Maybe you can catch it early!

The fan should be snug up against the alternator. There should be no play in any axis. Play on the horizontal plane means that there aren't enough shims. Play in the vertical plane means that either the alt bearing is shot, or the alternator isn't properly secured in the fan housing.

FA-18C · 03-29-2022, 07:01 AM

Feels and sounds like the shaft, so seems like the vertical and lateral play is related to bearings. I do not think it is loose in the housing, but will likely find out this weekend.

911obgyn · 911obgyn's Garage

When my bearings went it sounded like i was being followed by a jet!

FA-18C · 03-29-2022, 09:31 AM

It sounds like when the belt is a little loose, but it is correct. Once I get some bandwidth, will change out and have the current one rebuilt. It that is not it...well, I will keep hunting.

LIRS6 · LIRS6's Garage

I would think there shouldn't be any play in the fan. My alternator bearing failed at about 6K RPM's - scared the crap out of me ("what the hell was THAT?"!). Fortunately I was close to my house, and was able to limp home. My thoughts - don't wait for it to fail. You have the spare on hand - why not use it and save yourself a tow, or worse.

Jason

FA-18C · 03-30-2022, 06:32 AM

LIRS6 - that is the plan this weekend. I am going to first install a new FPR, then pull the fan and shroud when I replace the alternator. Will go ahead and clean those up a bit, scrub and steel wool with compound, then apply Gibbs. If upper valve covers come, will do those as well just to tidy things up a bit.

Locker537 · 03-30-2022, 06:42 AM

Does it sound and feel like this?

https://youtu.be/ImgCNNnkny0

If so, it is time to replace.

FA-18C · 03-30-2022, 07:11 AM

Locker - I have not popped my belt off yet, but the slight "rocker" is pretty dang close. It is noticeable, but not a full on howl yet. Going on this weekend - that is the plan. Drove to work today, and likely Friday, OTW this and FPR install are my WE tasks (as long as wife's spring gardening does not consume my time...)

30westrob · 30westrob's Garage

Remove the belt completely and you can get a better feel for the alternator bearing condition, then run the engine for a very short time without the belt to here if the noise is gone. Rob

FA-18C · 03-30-2022, 09:10 AM

Thanks Rob - plan to do that before going overboard.

Locker537 · 03-30-2022, 10:11 AM

Check if you have a rebuilder in your area.

I found a shop that rebuilt my original alternator. They did an excellent job and it was much more affordable than buying a new one.

FA-18C · 03-30-2022, 11:32 AM

I have a replacement that is rebuilt, and have a shop that rebuilds for Navy customers in the area - great on starters as well. Plan to send back a core from the shop and keep the rebuilt on my "spares" shelf in the garage. Same with CV axle I will replace. I like to have spares...

'78 SC · '78 SC's Garage

If you have a small amount of bearing play, it could be due to failure of the "tolerance ring" on the rear bearing. The rear bearing is not pressed into the alternator housing, but floats in an opening and is held in place by the rim of the plastic tolerance ring.

The original tolerance ring on my '79 failed last year (after 43 years of service) and the resulting (noisy) movement of the rotor ultimately destroyed the alternator. Here are photos of the failed tolerance ring, the exposed bearing behind it and an alternator with an intact tolerance ring. The rings are cheap, but somewhat difficult to find. An alternator repair shop might have the part.

failed tolerance ring

exposed alternator bearing (note gap around bearing)

alternator with intact tolerance ring

I found it hard to believe a plastic disk similar to a milk jug cap is used to maintain a critical tolerance like this.

FA-18C · 03-30-2022, 05:01 PM

Belt off - confirmed the sound from Locker's video, so I went ahead and pulled the fan and housing. Alternator looks to be in good shape, other than the bearing, and was charging just fine - so will get that rebuilt.

BUT - for the life of me, I cannot get the fan and alternator off the housing. What voodoo magic is required? Will take to our marine shop tomorrow and see if there is a 3-arm puller because I cannot see a way to press this out...Maybe one of my mechs does...

Once that is done, will take a serious hot lap on the housing and fan to clean them up. Do not think I am going to cerakote at this time...but maybe.

Any ideas are welcome - and thanks for the help thus far.

Superman · 03-30-2022, 05:21 PM

Take the fan off the alternator shaft. Then take the housing and alternator out of the car. Remove the small nuts that hold the alternator to the housing. Put some rags on the floor, and put a piece of wood next to the rags. Turn the housing upside down and carefully tap the edge of the housing against the wood block, all the way around. The alternator will fall out.

pampadori · pampadori's Garage

After you removed the air deflector thing on the back, you should see those long m6 bolts sticking out the back. Use a drift and hammer and tap them. This will push the alternator out of the fan shroud housing. You can set the assembly over some wood 2x4s to make room for the alternator to drop out as you tap the bolts.

Locker537 · 03-31-2022, 05:58 AM

Quote:

Originally Posted by FA-18C

Belt off - confirmed the sound from Locker's video, so I went ahead and pulled the fan and housing. Alternator looks to be in good shape, other than the bearing, and was charging just fine - so will get that rebuilt.

BUT - for the life of me, I cannot get the fan and alternator off the housing. What voodoo magic is required? Will take to our marine shop tomorrow and see if there is a 3-arm puller because I cannot see a way to press this out...Maybe one of my mechs does...

Once that is done, will take a serious hot lap on the housing and fan to clean them up. Do not think I am going to cerakote at this time...but maybe.

Any ideas are welcome - and thanks for the help thus far.

If I remember correctly when I did this last year...

I threaded nuts back into the studs on the rear of the alternator and tapped on them with a hammer to get the fan+alternator out of the housing. Support the assembly by the housing so the fan+alternator can fall free. The nuts protect the studs while tapping away.

To get the fan off the alternator, do the same thing. Support the assembly by the rear edges of the fan center (not the blades) and tap on the alternator shaft.

FA-18C · 03-31-2022, 06:37 AM

Brought it to work - the guys want to use the press vice dropping or banging on it... I have hope.

FA-18C · 03-31-2022, 12:21 PM

So - no offense meant to the pros on this board, but my alternator was essentially welded to the housing. To get the fan off, I ended up tapping the holes either side of the key way and pressed it out. Fought ALL the way to the end.
Now the alternator should be easy - nope. Took all of the long-bolts out. Still no amount of dropping tapping, beating hammering moved. Seated tightly in the housing. So I sacrificed the alternator completely - disassembled bit by bit until just the back mounting plate was left. You guessed it, still welded in there. Heat and tapping finally let it give way to join the pile of parts from the old alternator. You can feel the ridge where the housings meet- nice little environmentally welded parts. So now to clean it up and hope everything goes back together well.