ebs

When driving my 928 with the air conditining on, I am hearing some very strange noises. A real whining sound. It also seems to be more common when braking. I have tried to listen for the a/c belt with the car idling and then even revving it with the bonnet up, but there was no noise when trying this.

Any idea at all? All replies appreciated.

SteveG

You get noise only with a/c on?? I assume you checked the belt and perhaps sprayed some WD40 on it? If the noise persists, I would be checking the pads and bearings. Is it metal on metal? Pls excuse the dumb question, but some(?) pad have warning device built in that when worn to low level scrape the rotor, sometimes first heard in reverse. How old are the pads? Can't imagine any connection between a/c and brakes, but I would get brakes checked out.

ebs

Thanks for your reply SteveG. I can't see the connection between the brakes and a/c. It must have been a repeated coincidence. I just need to work out where it is coming from within the a/c unit or belt.

Brakes recently checked. Rear rotors skimmed and pads replaced. After one done, car and a/c seemed fine. This problem has appeared about a month after the brakes were done.

The sound is a whining noise that comes and goes, not really metal on metal. Any further ideas?

MikeN

Long shot here, but is the whining coming from the sound system?

When the A/C is on and you apply the brakes.......there is a pretty good
current draw on the alternator. If the sound system (radio) is non stock and not grounded / shielded properly you will get more and more whining noise as the alternator is working harder.

Turn down the volume all the way on the radio, turn on A/C and headlights, close all windows/sunroof. Rev engine a bit.......do you hear the whining? Does it increase with revs?

bd0nalds0n

Since belts require friction in excess of the reistance associated with driving the pulleys in order to do their job, and slipping is usually what causes whine/squeal, I would not think it advantageous to spray WD-40, a lubricant, on a slipping/squealing belt. While it might reduce squeal, it would be because the belt now has further reduced friction and can spin on the pulley without squealing.

A/C Bearings?

I noticed on my own recent brake job, during which I liberally applied "brake squeal stop" which comes in an aerosol can and seems to harden into a sticky, plasticky goop, designed I believe to create a barrier between the metal caliper pistons and the metal brake pad backing (thereby limiting squeal), that after a while the pistons compress through the goop, restoring the contact between piston and brake pad, resulting in sporadic brake squeal. I noticed the same thing on the old pads--the PO had installed Mintex pads which come with a liner that slips between the pistons and pads--and the pistons had worn through the liner. The Mintex pads squealed like crazy.

SteveG

This is a common wrench's trick. The WD40 is a temp fix for any squealing belt, I emphasize temporary. It does not solve the problem nor damage the belt, w/limited use. It will help determine if the belt is the problem. I guess I should for your sake, add, YMMV.

Joe '87 S4

My a/c blower motor would squeak and whine louder when I would step on the brakes. I actually just came back from picking up the car after having a new blower motor installed. Big difference in the amount of air coming through the vents now plus the dreaded squeak is gone!

Chris Prack

How about a vac. leak? BTDT. When you are on the power brakes it can change the amount of vac. at the source of the leak and may then create a noise that you don't hear with high vac.

Just a thought.

ebs

Thanks for your replies. The sound no longer seems in any way related to braking. It is intermitent and is most obvious in the first minute or so when first turning on the a/c. Any further suggestions would be appreciated please (I am very mechanically challenged).

Gretch

Sounds tantamount to clipping the green (steves is black, so is mine, probably) wire to the TB tensioner to cure the central monitoring console from reporting a loose belt. Oil soaked belts are usually junk too. Lamo technique if you ask me.......If absolutely necessary, I would rather see water sprayed on the belt, if for the purpose of diagnosing which belt is squealing.......

It strikes me that giving advice out like that is not in anyone's best interest, there are some really mechanically challenged folks here who just might take said advice.

SteveG

Gretch, This is hardly worth the effort as I don't share your opinion of the shark owners here, but anything is possibe I suppose; I guess any technique could be abused; someone must have put words in my post that aren't there. I did not say "soak" nor "repeat as needed." I don't know where you got that.

Using it as a dianostic tool is not comparable to cutting the green wire. BTW, mine is black, don't want some "Lamo" out there to think they can cut any black wire instead of the green one you warned them about. YMMV

Gretch

's ok, reqasonable people can disagree.......no hard feelings, and none intended. It is the advice that is lame, the trusting shark owner is "unfortunate".

Ever tried using armour all on your tire treads?, don't "soak" them in it, just put a little on.

This advice is only for "steve", no one else should do it, because it is "lame" advice.

SteveG

Gretch: No problemo = I've never had or used Armour All, so I have no possiblility of fooling with it. I just don't like the stuff, wouldn't use on a cheap car let alone my Pcar.

bd0nalds0n

I was told by a friend who sells tires that they all come with a thin coating of silicone on them, and you should be very careful for the first several miles until the coating wears off. If you've ever purchased shoes with new, slick and shiny leather soles, you may notice a similar effect walking across smooth floors...they need to get scuffed up a bit to grip.

I'd rather just SC the car to achieve the same kind of armor all effect...radical wheelspin

Joe '87 S4

There was a message board post on some other message board about a year ago with someone who put Armour All on his treads. He was asking for advice, after having been in an accident, *IF* they believed the Armour All could have been the problem... The replies were hilarious.