vicrattlehead

....Does it sound like a bearing trace wearing out? I took my vette out for a drive today and half way through I start hearing this noise like bearings wearing out. It's most pronounced at idle up to about 1500 RPM and then it disappears. When I popped the hood, the noise certainly sounded like it was coming from the alternator. I have no problem with electric delivery though, it's a strong 12 - 15 volts.

It sound like metallic radio static. Could it be anything else? I don't have an AIR pump, and it didn't sound like the water pump or AC compressor. Thanks in advance!!!!

lyonsh

You could have a bad diode - that wouldn't affect the voltage output, but could add a "ripple" that's not good for your battery. Get a mechanics stethoscope (or a long thin screwdriver) and listen to see if you can tell whether the noise comes from the front or back of the alt. Front = bearing; back = probably diode (although there's a bearing back there, too).

Rogue Wave

Another thing you could try is to remove the alternator belt and spin it by hand and see if that is where the noise is coming from.

Good luck :cheers:

tippi58

I had a real thrummm thrummm noise and one day the alternator up and seized. About 6 months later the water pump seized.:mad

Know what... a 350 chev will still turn that rubber belt. :lol:

I get a funny feeling a misalignment in the belt was the problem but >> :cheers:

:cool: :cool: :cool:

UKPaul

Could the sound also be described as a loud hiss (like the sort of noise escaping steam from a steam train makes)? If so, try giving the alternator a slap! I jest not :) Mine started making a loud noise (thought it was a severe vacuum leak at 1st) last year. It was intermittant, but when it happened I could hear it above the noise of the exhausts. Eventually it did it when I had the hood open & I slapped the alternator - which stopped the noise! The bearings on my alternator seem OK (took it apart to check them out). It's like the noise you get from brushes rubbing on a commutator (sp?) when you turn it by hand, but very much amplified. The alternator is charging OK & has done 2000 miles with this noise randomly starting & stopping. I can't work out what's causing it - it's doin' me 'ead in!!
:cheers:

GaryS

I think you gave a very accurate description of the impending failure of a bearing. It is a unique sound. Fortunately, alternator repairs are fairly simple. If your electrical output is good, consider new bearings.
Gary

chuck d

Try running the engine with the belt off. If the noise goes away you know you have the culprit.

Chuck D

NHvette

If the alternator is making a whirring sound, then the front ball bearing
is likely starting to let go. When that alternator locks up, the belt will lose.
Ask me about the wife's Blazer that I ignored for too long. I had to drive
three hours to Vermont to fix it for her in the 0 degree cold.

Even if it stops and starts, you should consider replacing it now. The bearing
itself is pretty cheap - and not much more to get a complete rebuild kit
for most chevy alternators. If you are worried about correct resto - then a rebuild kit may be a no no.

:seeya

UKPaul

I think I'll just change the bearings & see what happens. Better safe than sorry :)
Now that I've thought about it some more, I can describe exactly the sound that it's making: it's the sound that a small needle roller bearing makes when all lubricant has been cleaned from it & it is spun at speed. But a lot louder :(
Thanks
Paul