dereko

2003 996 C2 Coupe, 70k Km, car has suddenly develop what I can only explain as excessive road noise. Sounds like loud tyre noise, though has appeared quite suddenly. Sound could almost be described as a loud fan noise also.

Seems to emminate from front left side but hard to pinpoint

Switched off all Aircon, noise does seem to increase with speed, so whacked the car into neutral to eliminate engine noise and noise remains constant.

Immediately thought wheel bearing, so jacked up car one wheel at a time, and rotated wheels by hand, nothing abnormal until i get to the last one, front left.

front left definitively sounds different, like ball bearing rolling around.

The strange thing is, it sounds like ball bearings rolling around inside the actual tire, as at slow spinning speed noise seems contained at bottom of tyre, spinning it faster sounds like whatever it is inside rolls around perimeter of tyre more so

The strangest thing, quite loud though on the road once you get up to speed

Tyres are old but in about 80% of tread left. I'm guessing you are all going to say rip of the wheel and remove the tyre

I'm guess I'm just wondering if it is a wheel bearing is the noise just transmitting through the tyre, as it certainly sounds like a ball race.

Nickshu

Wheel bearing usually starts under load, making noise when turning only, but I have had a bad wheel bearing (on a non Porsche) just start howling during straight driving. I would start w/ a bad tire. Rotate the tires left to right for a short drive and see if it changes. Then go from there.

Mike Murphy

Sounds like a wheel bearing to me.

DBJoe996

Does sound like a wheel bearing to me as well. One question I have, since you said the noise sounds like it is coming from inside the tire, do you have the TPSM on your car? Maybe the TPS sensor broke loose inside the wheel. TPS=tire pressure sensor

dereko

Don't have a TPS as far as I know, didn't actually know The 996 had them as an option back then, but I'll double check, as it does sound like something inside the tyre.

I suppose the next simple step is take the wheel off and roll it around the garage floor and see if I hear the same noise with the wheel un mounted. And try and rotate the hub? Though I suspect I won't be able to rotate the hub very easily without a wheel attached.

They are GT3 wheels (quite lightweight) and the tyre does sound quite resonant when the wheel is jack up of the ground that's why I was questioning wether it might be bearing noise just transmitted acoustically given the illusion of being inside the tyre.

billh1963

If your tires are over 7+ years old change them anyway...source of noise or not.

DBJoe996

Good idea to take off the wheel and roll it around. The brake rotor should be fairly easy to rotate. Stick a lug bolt back in one of the holes. Rock the brake disc rotor back and forth, up and down. Check for debris between the rotor and the backing plate. Look for a groove in the rotor. Road debris can also get stuck between the rotor and brake pads. Check the brake pad thickness as well. I was just throwing the TPS idea out there. Mine (99) does not have TPS and I'm not sure when they started with that nanny system.

targa996

Yep - swap wheels side to side and see if noise moves with wheel. What happens when you turn right at 20mph ? More pressure on bad left bearing and you might hear change in sound - (window open )..

i had bad fromt bearing on Land Rover - made clicking sound when driving straight - but sound did not appear when turning and wheel did not rock on jack - which are two typical tests for bad bearing - but once I had. Bearing replaced sound went away . I guess the seals degrade with age, water gets in , mixes with the grease , metal wears , bearing shot !