My car makes a noise at stoplights when it is in drive and my foot is on the brake pedal. If I switch the car to neutral the noise goes away.

From my search on the board, it seems like the general consensus is a bad alternator clutch pulley.

Looking for a replacement alternator, it seems like there are two available. One is a rebuilt alternator, and one is a redesigned alternator.

Is one better than the other? Will both solve my problem?

Generally when alternators are rebuilt, don't they just change the electronics (Brushes, etc) Would a rebuild include the clutch parts?

What have you guys done, and how did it work out?

 

The clutch was designed to keep the belt from slipping over the pulley during quick bursts of speed and especially when putting an A4 in drive from neutral or park.The clutch is only found on A4 ( automatic ) cars. Engine torque is the contributing factor.. While the consensus on the forum may be a bad alternator clutch... I dont think so, because at idle, even if the clutch was toast, it would be like driving a car without an alternator clutch... and at idle there is no real engine torque to cause belt slip... You have another issue, in my humble opinion... you have two idler pulleys two auto tension pulleys, which may be drying up and at idle the grease does not lube the bearings .. its not until you get some load on the bearings that they quiet down.... you may just have a belt issue, or a harmonic balancer that is going south... These are just some of the issues.. you also have bearings in the compressor, alternator, water pump etc.
Good Luck
Bill aka ET

 

I agree - you have a tensioner pulley, and idler pulley and another set down low for the AC compressor. I would check them all.

 

How can you tell which pulley is to blame. I've tried listening but it is hard to discern which one is making the noise. Can you spray something on it for a temporary fix or should I just replace both the idle and tension pulleys?
I would probably have the dealership do this.

 

Does it do this all the time?
Can you make squeal in your driveway?
If so...
here is what you do.
there are two belt systems
the drive belt system and the ac belt system,
start the car and make it squeal..shut the car down,
Then remove the brive belt. Start her up again and see if she still squeals..
it wont hurt anything.
you will get some codes but you can reset them,..,
if the squeal is gone then its your belt drive system or something in that system, tensioner, powersteeing pump, alternator, water pump, idler pulley.
if the squeal is still there then its the ac belt system, compressor clutch, balancer,tensioner,idler pulley.
you can take off this belt to make sure the sound goes away..and verify its this belt system..
Once you determine which belt system is at fault you can use stethoscope to determine which component is singing. if you can not determing which component is singing then its the belt...

 

Those are all excellent Questions. Here is one of the posts I found that lead me to believe it is the Alternator Clutch pulley.

http://forums.corvetteforum.com/show...=neutral+noise

It's funny, when I was doing a search for that post, I found out my car (a 98) doesn't have a clutch pulley. The alternator was redesigned in 2001 (And they added the Clutch pulley) because people complained about the noise I'm complaining about.

If I read this post right, If I get a new style alternator, I have to have my PCM flashed. Is that what you guys get?

 

Take the advise in post #5 from ET before spending money to locate the problem!
Bill knows what he talking about...........
BTW good to see you back Bill.

Bob

 

Hey Daryl; how about updating your forum profile to include the year, and tranny type of your C5? A lot of info given here is year & tranny dependant. It's been reported that the one way clutch on C5's was only for the A4, and started within a certain model-year run.

You C5 may not even have an alternator clutch.

(I now see you finally gave the info: "I found out my car (a 98) doesn't have a clutch pulley.")

Please update your forum profile; makes it easier for everyone else