FredR

Recently, from time to time I have noticed a sudden, high pitched squeal that lasts about a second. I associate this event with going over a bump in the road - i.e. something that gives the car a bit of jolt. The sound initially appeared to come from the centre console and thought it might be from the stereo head unit but common sense dictated this could not be the case as there are no speakers in that vicinity. Over the last week or so the noise seems to be occurring more regularly and I suspect it may be emanating from the transmission tunnel.<br /><br />Given we know that sooner or later the torque tube bearings or their holder start to fail does my description align with known characteristics when this happens. I can believe that what I am hearing may be the bearing carrier spinning within the tube or the bearing itself protesting although why it would initiate and then stop a second later defeats me.<br /><br />Any thoughts?

James Bailey

Any possibility that your driving style is frightening your passenger ??

FredR

It would be nice if I had a passenger to frighten!

My wife does not like cars with a low down ride and firm suspension but on the positive side I do not get nagged whilst driving it.

Edit- on the other hand your comment reminds me of something I experienced many years ago in my late S4. In those days I liked to push the envelope as it were from time to time and never battered an eyelid doing do. Whereas I liked the performance of the S4 I never felt it was a fast car until - one day the local maintenance supervisor [a good friend of mine nowadays] took the thing for a test drive after I asked his opinion on something. Being sat in the passenger seat with no control and nothing to hold on to changed my perception of the car's performance- suddenly it felt twice as quick- not scary but somewhere close to the point where one puckers up. Whether that was just me or a normal reaction no idea.

The Forgotten On

I know this sounds a bit silly but have you checked over your HVAC vacuum system? When the valves go they can squeal.

Constantine

Hi Fred,

The quote above is a greater possibility than bad TT bearings given your symptoms.

Bad TT bearing noises will usually always be there and just get worse with time. Never heard of bad TT bearing noises when going over bumps and I have heard a lot of bad TT noise symptoms from owner over the years.

Given the great fun I've had with the repair of 928 HVAC systems, I would almost rather do a TT R&R. Almost...

Good luck with your search and please let us know what you find.

AirtekHVAC

FredR

Blake,

There are no "silly ideas" when one does not know what one is facing - all contributions appreciated. Not sure if you refer the solenoid valves or the diaphragm actuators - a couple of those are shot.

Your post jogged my memory to something that happened with my BMW 535 way back in 1990. That had a bit of a screech occasionally caused by the blower motor. The noise I am hearing is definitely caused by something rotating [or so I believe] but it does not seem to be engine or road speed related. Of course any noise from the blower is going to be carried through the ducting of the HVAC unit. If nothing else I have a spare blower unit from my late S4. Maybe this is could be the root cause?

Adk46

I discovered a mouse nest in my bell housing while doing my TT, so if I were you I'd go ahead and get new bearings.

davek9

My vote is for the Inside Temp sensor motor mounted behind the console, they will react to bumps and will squeal
Next would be a small hole in one of the HVAC vacuum pods..

Dave

FredR

Dave,

That is an interesting suggestion- directionally sounds about right location but had no idea there was a motor in there - is it some kind of fan that sucks air so as to blow it over the sensor? Sounds like a dash out job - urrgh!

Given our climate I run the a/c all your round but not on temperature control- if it gets too cold I either switch the a/c compressor off or turn the blower down so maybe I do not need that functionality. Is there an easy way to isolate this motor- presumably it does not have a dedicated fuse to remove? I have no heating circuit, the recirc flap is wedged [almost] shut, the head unit was dodgy so I am now operating the head unit from my late S4 - the hit list keeps growing as I try to find work arounds! I removed the HVAC unit from late S4 after it wrecked whether or not I could get one of those damned thing back together and working again might be a different story- looks like one hell of a job. Maybe it is one of those things that looks harder than it really is?

Rgds

Fred

davek9

Yes Fred the little motor is mounted vertically placing most if not all pressure on the lower bearing and they do react to bumps,
It pulls the cabin air in past the sensor mounted in the dash vent.
The entire dash does not need to come out, but the console does to access the screws holding it to the back of the console

I have a car doing it now and then, but getting worse, turning off the HVAC is the only way to stop it.

Dave

FredR

Dave,

Given I perceive that I do not need the functionality of the temperature sensor as my a/c is going ***** out in the hot months, is there a convenient location to interdict the power supply to the motor and shut the critter down? If nothing else if the squeal disappears I'll know what it was. I can fix the thing later during another cool season one of these years. That or I need to install an a/c in my garage!

davek9

You may be able to unplug the motor via the right side console carpeted access panel?
Not sure as I never tired it, and I do not know what that will do to the functioning of the HVAC system, I do know that the sensor needs to be in-line (connected).

If that works, that's what I'll do too until I pull my dash to get it recovered, need to get the twin screw sorted out first, there are priorities

Dave

FredR

Thanks for the input- I will have a dig around in the wiring diagrams and behind that panel - it always seems to be a bit of a dog's breakfast behind there. I chucked my spare HVAC panel during the last house move as I had limited space- probably a bad move!

9two8

Your query reminds me of a very similar issue I experienced a few years back now, every now and then the car would issue this high pitched shrill whistle sound, similar to a spun bearing sound / or a fast rotating steel wheel rubbing on some metal, then it would just go as quickly as it came.
Mine too seemed to be coming from the centre to bulkhead area.
We never sourced where the noise was coming from exactly, safe to say a few weeks later the air-con compressor failed ie, completely burned out. After that was replaced we never ever got that noise again .

Ken
80 928 S
5 Speed
UK