Describe the noise a failing alternator would make

Hold a dowel rod or long screwdriver to your ear and then to the various accessories, pulleys, etc and try to locate the noise. Be careful not to get it caught in the belt or moving items. make sure your tool is long enough (no, not that tool) to keep hair, clothing etc clear.

When Ive had alternators fail with a "noise" (they usually dont make any noise), it was a loud whining noise.

That does not sound like an alt problem to me.

It sounds to me like engine pinging from bad gas. Does it come and go when you step on the gas or climb hills?

I'm bringing up this noise issue again....still happens intermittently. Comes & goes. It sounds like a metal on metal rattle/ping, or like fine gravel in a metal can being shaken. I'm sure its coming from the right hand side of the engine compartment. While it was happening yesterday I popped the hood & took a look. I can't see anything out of the ordinary. But I'm sure its coming from near the power steering pump.

Would a power steering pump makes this noise? I know it would make a whine if it was bad, but what about this sort of noise? The pump is loud to begin with - I can hear it whenever I turn the wheel, not just when I crank it.

Might be one of the bearings on the serpentine belt (alternator, P/S pump, A/C clutch, idler or tensioner). A stethoscope would help narrow it down.

if you want to start throwing parts at it, start with the idler first, its the cheapest!

When you use that home made stethoscope on the alternator, the bearings will rumble slightly. That is normal because the brushes inside are riding on the equivalent of an armateur.

Water pump should be very smooth. P S pump--I can't remember, but probably fairly smooth. You can also check the noises from various parts on a second car.

Watch your fingers and that dowel or stethoscope. Easy to get injured.

Good luck.

z06bigbird said:

Watch your fingers and that dowel or stethoscope. Easy to get injured.

Good luck.

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Ears too. Kinda smarts when you get an 18" screwdriver too close to the moving belt and it kicks back into your head :thepan:

Turn OFF the a/c... I bet it will start to sound continuously. That's the noise a failing a/c clutch bearing will make. The pulley will tilt a little and touch the clutch plate when it's not engaged.

Krashed989 said:

Turn OFF the a/c... I bet it will start to sound continuously. That's the noise a failing a/c clutch bearing will make. The pulley will tilt a little and touch the clutch plate when it's not engaged.

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My a/c is always off. "Low refrigerant" message. Even though I had it fixed. Whatever. Could this a/c clutch bearing still be the possible cause even though my a/c doesn't work?

Its tough to use a stethescope to listen when the noise happens randomly. And it never seems to happen at a convenient time. Somedays, I don't hear it at all. Other days I hear it often.

The A/C clutch spins whether the A/C is on or not. An electromagnetic clutch engages when it is turned on and then spins the compressor as well.

Lesley, I replaced my alternator last year as the bearings really did go bad. It made a continuous "whine" and was not intermittent as you describe. Mine also did not have a charging issue - I was able to change it out myself...not the easiest thing on my 97 SLS. I also thought it was the power steering, but found out that a low rattle (intermittent) was actually something called a "Y" tube underneath for the exhaust. The dealer raped me on that one, and I'm betting I could have gotten it done cheaper at muffler shop.
If you need to replace the alternator, give yourself a Saturday to get it all done - it's easier if you have small hands too.

Lesley's93STS said:

My a/c is always off. "Low refrigerant" message. Even though I had it fixed. Whatever. Could this a/c clutch bearing still be the possible cause even though my a/c doesn't work?

Its tough to use a stethescope to listen when the noise happens randomly. And it never seems to happen at a convenient time. Somedays, I don't hear it at all. Other days I hear it often.

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That's interesting.... Yes it could be it, but I would expect it to be constant with the a/c off, not intermittent. Try turning the a/c on for a few seconds and then back off again to see if that triggers the sound. Maybe you still have defog on or something.