Hey I've noticed recently a moan as the car is bearly starting to move from a dead stop. It comes from the front end I think and I can almost since it through the steering wheel (as strange as that seems). The best way to discribe the noise is to say it sounds kind of like The Queen Mary or a large Ship leaving port (it's horn noise - but not near that load ). I think people on the street could probably hear it - kind of embarrassing if I roll the car super slowly. I'm thinking maybe a slightly warped rotor but are there any common items to check for? This car has 911T front suspension and brakes btw. Also, this car sat for 3 years before I started driving it recently...but everything was supposedly renewed during a restoration (track prep) before it was stored for the 3 years, so maybe something has dried out a bit too much.

Doug C

a warped rotor would "pulse", and not be a constant groan....

bearing?
wheel rub?

Well, I'm thinking it is sort of a pulse, because it goes away and comes back as the car moves, again only very slowly from a dead stop. Once I'm rolling 5-10mph it's no longer there or not detectable anyway. It's like the car rolls into the moaning area and then out again.

Doug C

wheel bearing ....

Andy

I would say its either brakes or bearings.

both could do what you are saying, though more likely its brakes..

You could have glazing on the pads and rotors, you could have a bad piston in a caliper that is not retracting and is rubbing on the rotor...

To check the brakes, go to a parking lot and stop the car without touching the brakes....first get it to stop maoning...then either glide to a stop, or use 1st gear and the emergency brake to stop it without touching the brake pedal...

If after that as you are taking off and it moans, its probably bearing related...

Rich

wheel bearing ....

Eric

If it was a wheel bearing though, wouldn't I be able to wobble the wheel assembly while it's in the air - or maybe that's not always the case? I haven't tried it yet BTW.

Doug C

QUOTE (DougC @ Jan 18 2006, 03:00 PM)

If it was a wheel bearing though, wouldn't I be able to wobble the wheel assembly while it's in the air

only if the WB was lose ...
the "moan" you feel/hear is not a lose bearing, it's a bearing that is about to die.

two completely different things ...
Andy

If it sounds almost "harmonic", it might be a caliper that is hanging up just a tad? I had one vented rotor that lost the spring thingies inside the vents. It hummed all the time.

I'll check those things out guys - thanks.
Doug C

If you only hear it below 5-10 mph, then I'm siding with wheel bearing.
But then again, the tone of the sound may be a clue: growl = bearing, moan = brakes...
Does it change if you drag the brakes a little?
Jack it up and rotate the wheels while you listen.

The brake test isn't all that reliable. Wheel bearings can change noise from the load change when the brakes are applied.

Wheel bearings seem to fail in several ways, causing different noises. A loose bearing will cause a wobble. A bearing that's too "dry" or has a flattened roller will usually chirp or screech. A bearing that has a wear spot on the race will usually howl all the time, and generally get worse as wheel speed increases. Sometimes, the noise will change based on whether or not you're turning, as you load/unload the damaged bearing.

A loud moan at low speeds that goes away once you get moving, esp. if it only does it after the car's been sitting for a few hours, can be a slightly dragging caliper, perhaps caused by a light amount of rust on the rotor that quickly gets wiped away.

QUOTE

If it was a wheel bearing though, wouldn't I be able to wobble the wheel assembly while it's in the air - or maybe that's not always the case? I haven't tried it yet BTW.

Most of the time but not always. When I teched for the local PCA, I would rest my knee on the top of the tire and rock. You might hear a clunk.

My 911 died at the Historics at Laguna Seca. I thought that's what it was but it actually tightened up the assembly before going all the way. Made it hard to initially diagnose.

Either way, it sounds like one that's 'beginning' to go.