Failing alternator?
 

When I started up my Cherokee today, I noticed a strange sound from the engine bay that was RPM-dependent. It appears to be coming from the alternator (verified with mechanic's stethoscope), though the voltage output is normal. I drove about 30 minutes, and it's quieter but not gone. Perhaps it does better when hot, or perhaps it's resolving itself.

In any case, my next step when I get a chance is to pull the serpentine belt and see if the pulley spins normally. In the meantime, here's a video of the noise. Think my alternator is on the way out? It's about 6 years old and was replaced by a shop several hours from home when what I assume was the original alternator failed while driving, so I'm unsure of the brand.

Bearings? Internal damage? Personally, I'd check each pulley with belt off.

I pulled the belt off and spun the alternator pulley (and all the others). Usually, alternators will spin for a few seconds when you do it by hand, but this one would only do a rotation or so before coming to a stop. With the belt on and the engine running, there's definitely noise coming from the rear of the alternator. I'm guessing bearing or some other internal mechanical issue. Is it toast?

If so, I need to upgrade to a higher-amperage one anyway.

I have had several apart, (due to failed diodes. OEM units die after about 28 years apparently)

Usually they have a bush, sometimes a bearing, front and rear. (cant remember which)

These can be replaced, but I do not know what is included in the OH kit for that model, usually bushes/bearings and brushes, check ebay or local suppliers, or Youtube

It may be more economic to buy a replacement unit

Alternators are a real pest if they fail, so a spare is good to have

The last time, I lasted 1-2hrs, she lost power to the GB solenoids on the last uphill, I jammed it into 1st, as I rounded the corner for the long downhill home, the engine started misfiring, or maybe it was the fuel pump, another time my son left it parked on the side of the road, hundreds of miles away. I had to make my way there, spare (tested working) alt, tools, and drive it home

I'm thinking I'll just get a 136-amp alternator for a ZJ 5.9 V8 and replace the noisy one that's in there before it ****s the bed. I'm looking at either new or reman ACDelco alternators off RockAuto. Any reason I should go with reman over new?

Link to new: https://www.rockauto.com/en/moreinfo...2412&jsn=10525
Link to reman: https://www.rockauto.com/en/moreinfo...2412&jsn=10531

The AC Delco ones are built extremely well.

skip the 136 and go for the 160 out of the 2001 5.9 Durango, same size as the 136 and usually same price.

I've always had good luck with Pure Energy stuff.
https://www.rockauto.com/en/moreinfo...t=2412&jsn=954

I considered the 160-amp option, but I was wary of having to mickey mouse the wiring to get it to hook up properly. The 160-amp version uses a different connector than the 136-amp version.

Here's the 136-amp version with the same connections as the factory 90-amp alternator.
https://cimg6.ibsrv.net/gimg/www.che...f4487cbe03.png

And here's the 160-amp version.
https://cimg7.ibsrv.net/gimg/www.che...161d02741d.png

looks like they changed the plug in 99.. my 2001 has the same plug as the 160amp. Thought they changed it in 97 with the face-lift. Changing to the plug isn't difficult but I can understand not wanting to mess with the factory harness.

I ordered the 136-amp version so I wouldn't have to screw with the wiring. I'm planning to pull the old one apart to see if I can figure out why it was making that godawful racket. Will report back.

UPDATE:

I pulled the old alternator, trimmed the both brackets (aluminum and steel) as well as a tiny bit of the aluminum from the timing chain cover, and the bigger ACDelco 136-amp alternator fit in nicely. I did have to swap pulleys since the new one had an extra groove. Here's a video showing how loud the old one was. I'm glad I got it out of there before it locked up or caught on fire.

By the way, I pulled the old one completely apart, and I found the rear bearing was shot. That explains the horrid noise coming from the rear of the alternator.

You should SRIOUSLY consider upgrading the main alternator cable. My OEM cable with unknown age alternator, the cable/connector let go and burnt up.

I was lucky not to be stranded

What I am saying is 28 yr old wiring, which on an XJ, is known not to be the best, should be attended before disaster inevitably strikes

Its getting to the stage where electrical wiring issues are arising as "cause of death" for many XJ these days, try finding someone who will fix one

I do all my own work, and only know a few people I would trust to know as much as I do, but i been round longtime

I did! A while back. Bought cables off someone on here who used to make them (XJ_Wonders?). Battery terminals and all.

https://cimg5.ibsrv.net/gimg/www.che...40fb1424f6.jpg

quite a handsome engine bay too ! :)

LOL, thanks. It's either shiny clean or covered in mud. Nothing in between.