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alternator sounds like it's full of rocks

ehall

ehall

NAXJA Member
NAXJA Member
Location
Southern Maryland
Over the past week or so I've started to notice a rattling/grinding noise on cold start that goes away after the engine warms up. Today I got out the stethoscope and listened for the source, and it seems to be coming from the alternator. I assume there's some crud in the bearings, but at this point I'm just guessing. I have another alternator laying around here somewhere, so I could swap it out and take a look. Anybody run into this before?
 
Thinking about this more, I think I probably got some coolant into it, since I've been messing with the temp probe in teh upper radiator hose and that had a small leak. I'll probably try cleaning it with hose water on the jeep first. Anything else to try? Can't get worse...
 
Yep. My 95 did that this fall. As it happens, I had just happened to buy a brand new alternator on spec at the tail end of a yard sale, when the price went down to $4. Problem solved, my heep is now worth at least $4. Actually more, because it has a good battery too. I'll have to keep it running for another year or so to justify the expense.
 
were it mine, I'd probably rock the new one and replace the bearings in the old one at my leisure. I would also check the belt tension again to verify it isn't too tight since you moved the alternator up higher. Excessive belt tension is the typical culprit for rapid bearing wera (assuming the alternator isn't full of dirt/ rocks)
 
Belt tension feels fine, with about an inch of deflection in the top span.

It only makes the noise when it's cold out. Today we have a heat wave and it was 35 or so, only made noise for 5-10 seconds. Yesterday was below freezing and made noise for 30 seconds maybe a little more. Once it's warmed up it's perfectly fine.

I took it to car wash just a while ago and pressure washed the alternator and all the pulleys. We'll see what it does tomorrow morning.
 
Well I'd def. get a new one, and as mentioned tear apart the old one and rebuild. They sell spray electrical cleaner in auto stores, I used that on mine after it got mudded.
 
A few weeks ago, when it started to get serious cold, I heard the rocks, too. I could have sworn it was the alternator, because (so I thought) the belt would chirp whenever I turned on the A/C, until the engine warmed up. Thought maybe the alt. was complaining about the load the A/C put on it. Compressor seemed to be spinning fine. But, of course, the A/C quit this past summer, and now it's cold, sounds like a gravel truck under the hood. Took the belt off, started to spin pulleys by hand, find out it's the free-wheel bearing in the compressor clutch. Got a smooth turning comp. from JY, problem solved. (I can't understand why anyone needed to 'clunk' a cherry '95 two door with 54k miles, but the parts live on). This isn't the first pulley bearing I've had go bad, just another idea for you to look at.
 
I've put new bearings in old Delco alternators, but have never had a Nippondenso (is that what they are?) apart. With the Delcos, try to remove front cover without letting the armature move forward, letting the brushes pop out of their slots, and I'm guessing these are the same. Although, it might be nice to see if there's any brushes left, with as many miles as you have on it.
 
The only pulley that made any kind of ticking noise when unloaded was the old idler on the YJ accessory bracket so I replaced it with a new Dayco. The pulley bolt was also a little shorter than I liked and seemed to have some warble so I replaced it with a longer one that made the pulley more stable.

The alternator pulley seems to have a high preload on the bearing but spins smooth and quiet. FWIW the original alternator that I pulled off when I switched to the high-output ZJ model has some stiction and a tick so it would probably make even more noise. But if the noise is back tomorrow morning I'll try swapping it in and see what happens.

With tension on the belt, the only pulley that has a whine is the idler pulley on the tensioner, which is probably the one that was on the engine when I got it from the reclamation house so I ought to replace that one too.
 
Last edited:
Shorty said:
were it mine, I'd probably rock the new one and replace the bearings in the old one at my leisure. I would also check the belt tension again to verify it isn't too tight since you moved the alternator up higher. Excessive belt tension is the typical culprit for rapid bearing wera (assuming the alternator isn't full of dirt/ rocks)
Click to expand...
X2 on this, get a new one and keep the old one as a spare.
 
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