A couple weeks ago I noticed that the noise in my interior cabin significantly got louder. It sort of sounds like the droning/humming of tire noise(like the big pickup trucks with mud tires make on the fwy), and reverberates in and out every second. It seems to be coming from the front of the car. Being on the throttle or off does not affect the sound, but it does get louder at higher speeds.

I checked the tires and pressures and all seemed fine. Then I took it to my shop to put it on the lift to check everything. The only thing we found was that the mineral oil reservior was for some reason overflowing and leaking out. This is the little reservior with green cap that is in the front bonnet next to the brake fluid reservior. You have to remove the plastic panel to access the reservior cap.

I siphoned out some of the overfill, but that still didn't really explain to me the reason for my increased cabin noise. I don't even know what this mineral oil reservior is really used for. Power steering?

I'm thinking it could be a worn bearing if the noise continues to get louder and screetches, an out of balance tire, or exhaust leak? Right now I'm just driving it until something gets worse. Any advice would be appreciated.

Steve
01' 996TT

 

I just had the exact same thing 3 months ago... The tire guy told me the tires were feathered so I got new tires.. it made a bit of difference but not enough. It was sooo loud. so then I took it in.
They changed both front bearings and it is soooo quiet now.

 

I think Alan and wowgogs are on the right track - tires have a BIG impact on road noise. I've found certain tires make much more noise as they wear and if they are worn unevenly due to alignment, they will make more noise.

If your shop has checked wheel bearings, I'd look at the tires and brand - again, some brands are prone to noise as they wear...

 

Could be a bad wheel bearing or bad tires.

 

Thank you for the helpful advice. I'm using Continentals, SportContact2.

I think maybe I will possibly try and put the stock wheels back on the fronts to see if the noise goes away. If so, then it has to be the wheels. Otherwise sounds like it is possibly the bearing.

I still find it strange that the mineral oil reservior suddenly started overflowing out, since that hasn't been touched in awhile.

At least either way, the noisy tire or bad bearing shouldn't be anything to really worry about safety wise when driving right? As long as the tread is still good, then the louder road noise shouldn't be a safety issue, and a bearing would only get louder, but not suddenly snap I assume? Of course eventually I'll be replacing the tire or the bearing if it gets even noticably louder.

 

I don't know about the overflow issue (I've never heard of that), but I had a buddy who had a road noise problem that sounded exactly like your's: lots of humming coming from the front, got progressively louder with road speed (not engine speed). turned out to be a wheel bearing. Good luck. Scott.

 

If it is the bearing like mine it can be dangerous.
My mechanic said much longer on mine and the bearring probably would have blown up or seized and I could of had a MAJOR problem....