petr0lb0mb

It sounds like it's coming from either the alternator or power steering pump. On cold start, the noise isn't there and then suddenly appears after about a minute.

Thanks for having a look (er, listen)!

CARRJET

you can use a screwdriver to put tip on alternator or pulley and stick handle next to your ear to pinpoint noise. also you can take belts off to make sure its not main engine noise to narrow it down.

Smoken1

Sounds like a noise I have heard b/4. Check the alternator De-coupler pulley

Bill Curlee

LOL!! When I saw that the alternator had a alternator De-coupler pulley, That was going to be my recommandation.

Get 4 feet of 5/16 vacuum line. Put one end in your ear and point the other in the area of the noise. It will allow you to pin point the exact spot where its coming from.

If you jam a screw into one end of the line and put the screw on each component that is rotating, you will be able to Positively figure out what one is making the noise.

Dont forget to chech each belt tentioner.


Bill

LoneStarFRC

If you haven't already done it, remove the belt and start the engine. If you still have the noise, check the A.I.R. pump. It lives almost directly under that area. Below, and slightly to the rear of the headlight.

petr0lb0mb

Thanks for the tips and pointers everyone. I will go back into the garage tomorrow (it's 1am and I just got home, beat) armed with your advice and report my findings. I'm a dinosaur and so I had never heard of an alternator decoupler pulley before. Also, wasn't aware that C5's used A.I.R. pumps--I thought they disappeared in the 80's. Well, I hope it's not the A.I.R. pump as it costs twice as much as the pulley.

Thanks people. I'll back tomorrow.

jac1979

I just replaced my tensioner pulleys and lower idler pulley, the one on the ac belt. Mine was making the same noise, it just squeaked at first start up and went away but then just started doing it all the time. I also suspected the alternator but turned out not to be the prob.

petr0lb0mb

I have just repacked the grease on the sealed bearings for the tensioner and idler on the main belt system. I'm about to look into the tensioner and idler on the AC belt system now as I do hear squeaking coming from them so they definitely need attention anyway. Thanks for chiming in.

petr0lb0mb

Here's the update so far.

Bill Curlee

Well,,,,,,,,,,,,,,,,,,,,,,,,,,,,, I don't think GM engineered a decoupler to scream like a sick eagle when decoupling. LOL and that play is a little much. So,,, Theres part of your issue.

Lets try this. Drizzle some heavy lube into the decoupler and work it in. (Note! This may destroy an already bad decoupler) See if the lube stops it from making noise but continues to couple in the driving direction. You can always flush out the lube with carb spray or brake parts cleaner.

Put the alternator back on and see if the noise is still there or gone.


As for the Power steering noise. Cant say for sure that I have ever experienced that noise. The pulley is PRESSED on the shaft so, if the shaft and pulley are loose, theres a BIG issue.

The pump has a check ball in it and that could be making the noise if the spring behind the ball is weak.

Bill

petr0lb0mb

Thanks, Bill.

I have already have a new decoupler pulley on order prior to seeing your post. Additionally, I took the alternator to a rebuild shop to spin-up the armature and have a listen. It was noisy and they said I'd need a rebuild. Although I heard noise when they spun it, I'm not sure it was THE noise. Either way, I'll find out after this.

Alternator rebuild is costing $140 (including ADP).

They quoted me $170 for a PS pump rebuild.

And no the PS pulley isn't loose on the shaft. I think it's the ball you mentioned because it feels like that would feel (if you know what I mean).

petr0lb0mb

Update: A rebuilt alternator and decoupler pulley has solved the problem completely. The noise is gone. Thanks for the input everyone!

Bill Curlee

Excellent!! Good job!!

petr0lb0mb

Thanks, Bill! Have a good one!