(Posting in general engine -- let me know if this should be in a different board!)

Slowly beginning the process of revitalizing my old 1992 RS. After checking out the oil and fluids, I turned her on for the first time in a few years. There's a couple quirks that I'll try to get to later but the biggest one is this metal rattling sound originating from what sounds like the passenger side under the hood.

Any ideas? Below are links to a few videos so you can hear the sound -- mind the dust!

As a disclaimer, while I'm a technical person by nature and trade I'm still new to working on autos -- any help given is highly appreciated!

https://www.dropbox.com/s/m2r7lxjy97...%2013.mov?dl=0
https://www.dropbox.com/s/r8ekrxr5zl...%2024.mov?dl=0
https://www.dropbox.com/s/thh8z5ahw2...%2000.mov?dl=0
https://www.dropbox.com/s/ew20f18q0a...%2021.mov?dl=0

 

More than likely it's one of your front accessories, and I'm going to go out on a limb and say air pump since they love to go bad on our cars. I'm not familiar with V6s, but could also be alternator, power steering pump, water pump, or a/c compressor. Whatever it is, the bearing's bad, and the entire assembly needs to be replaced. Easy way to rule out the a/c compressor is if the noise goes away when the climate control is set of OFF.

 

I'd say Navy is on the right track. I'd pop the belt off and turn each of the accessories by hand until you find the one that feels crunchy. Just from personal experience, it'll never be the power steering pump, because they don't really fail, just leak. Could be the A/C clutch bearing but never had that either. I've had more than a few smog pumps lock up, but usually while they're laying in a box in the back of the garage. When the alternator fails, they'll usually spit the 10mm bearing out the back. And when a 3.1L looses the bearing in the water pump, they like to ram the impeller into the timing cover, which is usually enough to drag the drive belt bad enough, you start to notice the power steering cutting out. LOL

Honorable mention goes to the cat converter. They like to fail spectacularly resulting in all manners of rattling, but then that noise would be coming from under the car, not at the front of the engine compartment.

 

I know that sound!

That’s the alternator dying.

 

This is imminent.

 

Kits to rebuild alternators are inexpensive if you car to tackle a rebuild.

I put a new made-in-Mexico Autozone alternator in my V6 Sport Coupe. Been a year now, and all is well.

 

If you catch that failure early enough, you don't even need a kit. That bearing is the cheap one, available at nearly any bearing shop. Hardest part is getting it off the shaft. Last couple I did, I just cut the races with a Dremel cut-off wheel. Press on the new bearing, reset the brushes, and reassemble. Good to go until the next failure. I got 3+ years out of the last bearing failure.

 

 

Shouldn't need to pull it off to see if it's a bad bearing. Literally just look at the back of the bearing. If you see *****, black/gray powder everywhere, or the seal melted and bulged out or hanging by a thread, the bearing is bad. If you take the belt off, and spin the pulley and it makes grinding noises, the bearing is bad. Don't just go throwing an alternator at it until you diagnose the problem a little bit.

 

 

Slight grinding noises (not super crunchy) when I turned the pulley so I wanted to investigate more. Pulled the alt off and saw a lot of black powder caked on and around the bearing. There are some clicks and squeaks coming from it that seem to indicate impending bearing failure.

I'm intrigued at the idea of popping off the bearing instead of dropping $100 on a new alt -- I'll have to do some quick research on how to dis/reassemble the alt without mucking anything up.

 

Some noise can be normal, brushes will make a little noise, but any lumpy or grindy noises would be a good indicator. Just give everything under the hood a spin or two, and it should be easy to find any faulty bearings.

The rear bearing is a 10MM X 26MM X 10MM. Last ones I bought were WAI#: 6-2000-4. Should cost between $10-15.

Remove the three case bolts, and the back half of the case should crack free and slide off. You'll hear the brushes spring out when the case clears the bearing. Straighten a paperclip, push the brush springs and brushes back in their holder, and slip the paperclip thru the hole to keep them in place.

The rear bearing will generally stay on the shaft. There isn't much room to get between the brush contacts and the bearing to get the old one off. I usually end up splitting the bearing races with a cutting tool. Getting the new bearing on is fairly simple, it's a press fit, so it can help to heat it up a little with a hairdryer or heat gun then drive it flush with the rear of the shaft.

Make sure you're paperclip extends out of the case at the rear, reassemble the case, and pull the paperclip. Turn it by hand and it should be smooth.

Now the front bearing is a bit more involved because the pulley has to come off, and the bearing can be somewhat permanently installed in the case if it hasn't been rebuilt before. Other optional steps would include replacing the regulator, brushes, polishing/cleaning contacts, blah, blah, but that's up to you.

 

Update as of Sun 3/18 -- Thanks Drew for the detailed steps for switching the bearings and checking the other forward accessories.

I tried spinning the AIR pump and it's very difficult and crunchy. I'm now undecided if it's the alternator bearing or the air injection pump. I don't have enough experience to determine if the air injection pump is supposed to be difficult and grinding to turn -- my gut says no but here's a video trying to capture the sound of both the alternator spinning and the air injection pump spinning:
Again, here's the engine running: -- which one of these is the more likely candidate?

 

The alternator doesn't sound great, but the squeek is pretty typical for the brushes, and it certainly spins freely enough. The smog pump is much stiffer and more noisy than I'd expect.

Might want to start it up for a moment or two with just the belt removed to eliminate the possibility that it's not one of the accessories.

 

Ran her for about 10 seconds with no belt -- no rattling or abnormal sounds at all!

So I have the steps to replace the bearings on the alternator (or just the whole damn thing)... how do I replace the bearing(s) on the smog pump below it without buying a new one? Is that possible? Doing some research now.

 

I've never gone into the smog pump. If you still have the stock catalytic converter, I'd probably fix it, or find a replacement. I haven't looked recently but last time I looked on Rock Auto, remanned smog pumps run around $100. Better bet would be to find a good used one, since most people have no interest in running one.

 

Also running an Autozone alt in my V6 Sport Coupe, haven't been stranded in over 4,000 miles