2002M3Drew

I did a DE this past weekend at Lime Rock with PCA. My car passed the pre-event tech with flying colors.

On the track, the car would work perfectly for around 10-15 minutes, and then it would start to develop a slight change in the steering feel, and this would progress into a sound, soft at first, and then getting louder. The sound was smooth, not a lumpy sound. At first the instructor couldn't hear it, but by the end of the lap it was easy to hear. Going down pit road to the paddock it still made the noise, even in a straight line. When I truned the wheel sharply left to right the sound would appear and reappear...this jerking the wheel afffected the sound.

We checked everything out, including jacking the car up and playing with each wheel separately for play, and nothing was glaringly wrong (this was actually done by a Porsche mechanic, there for the DE event as well). Then again, everyone was quick to point out that bearing can make noise under certain conditions before they actually get to the point where there i obvious play in the tire/wheel.

I went out in my next run group to see if parhaps the problem had corrected itself, anf the car again ran fine for around 10-15 minutes, until it began agaion, and in the same manner...feeling it first, and then hearing it. I repeated this again in two other run groups, the last one with yet another Porsche mechanic driving the car.

The mechanic who drove the car was really unsure about the bearing diagnosis, and suggested checking under the grease caps for lubrication...it seemed to him that they might actually be dry. We checked this, and they seemed well lubed. So, that was that...it was a two day DE, but I called it quits after 1.

So what does everyone think? Is there perhaps another obvious or less-obvious are to check out? The main points here seem to be that there is a vibration...almost a binding up feel...that develops in the steering in direct proportion to the harmonics, and that the noise seems to be heat related, proportionate to the extra stress the car takes on the track (it didn't make any noise on the 2 hour ride home). The car is lowered, it has fresh turbo tie rods, bump steer kit, relatively-new Bilsteins with only 8K miles on them, and a steering column bushing was recently repaired as well.

Any opinions appreciated!

Noel

That does sound strange. I initially thought about a lubrication isses, since it came on with the heat of 15 minutes of run time. The question I have is, did you notice it on the drive home?

2002M3Drew

No, it was absolutely fine on the ride home, all the way at highway speeds. We didn't check the inner bearings because we didn't have replacement seals or anything...don't know about the lube situation there. Both fronts looked OK.

I thought it might be something in the steering rack, but it would make the sound even in a straight line (when no sideways pressure was on the rack). Since also relating to motion, I figure it has to be something relating to the wheels and/or axle.

Noel

I still think it sounds like a lube issue that was caused by the extreme heat that is transfered to the hub at the track. Pull the rotor/hub and look for the tell-tail signs of overheating like bluish coloring on the spindle or bearings. Good luck and post back what you find.

wwest

Brake piston seizing.

2002M3Drew

WWest...that's a new one on me! Can you tell me more? I did notice that I would get it to make the noise quicker than the instructor, and being a novice track person, I'm braking too early and often...this might be the ticket.

wwest

In my 78 Targa I thought I had lost a right front wheel bearing by it turned out the inside caliper pistion was not retracting, remaining "engaged", pushing the rotor sideways against the bearing.

Noel

Interesting, however, I assume that with that much force on the rotor, the fluid would boil and he would feel sponginess in the pedal. Also, shouldn't he notice pulling to one side under heavy braking?

Just a couple thoughts.

Obviously, the sticking piston would be easy to test. Just jack up the front of the car and spin each wheel to see if it spins freely.

wwest

AS Shelly Berman once said....

"What is the sound of one hand clapping?"

Pad pressure on only one side of the rotor doesn't brake the wheel as much as it does put pressure on the wheel bearing........

NOISE!

Noel

Would it not still transmit heat from the rotor into the caliper and thus into the fluid? In a track situation, this would be the case since the pad would never loose contact with the rotor. This effect could also still be felt by spinning the wheels while off the ground since the force necessary to effect the wheel bearing while the weight of the car rests on it, would be significant enough.

However, the pressure may not be enough to cause the bearing to make noise, but enough to make the rotor make noise while rubbing against the pad. In fact, this could make sense if you think about the caliper piston seals changing under the heat of 15 minutes of track driving and thus causing the piston to stick, but only when it is hot.

Sorry, I have no quotes that are applicable.

2002M3Drew

That's an interesting idea. Well, I have another track day (actually two) this weekend, and this track has harder braking zones (Pocono North Course). I did the bearing job last noight, and I'm also replacing the front pads since they seem a bit low. The bearings were definitely not dry at all, but there were some signs that the left front was cooked a bit more than the right. Since this car is new-to-me as of 5/04, and there are no PO records of a front bearing job, I figured it was good preventative maintenance.

I did notice smething interesting, though...the front brake pads were very low, particularly the rear pad of the right caliper. I'm wondering if the piston is seizing up a bit with high heat and thus wearing this pad more, or conversely, if that pad just wore down and the lack of enough pad contibuted to the noise. When I pull the pads tonight I'm going to look hard at these...that might be the problem.

Thanks for the ideas, guys!

Richard Pankhurst

I have an '89 Carrera and had a front right wheel bearing let go (i.e. disintegrate) on the way home. Before it let go there was a "growling" sound around LH corners and at high speeds on the freeway (>50 mph) which was bearly noticable but I tracked down to the bearing. I had to have all the bearing parts and the strut replaced (as the spindle was damaged). Even now I think the replacement has not gone well as the noise is back to a much lesser extent. I check for play in the wheel bearings when I change tires and pads at the end of the weekend and I have the bearings adjusted before every track event and periodically otherwise. If the hubs or spindles are not damaged the bearing races are cheap.

Good Luck

g-50cab

I'll 2nd the sticking caliper piston - especially as your brakes are heating.

2002M3Drew

Well, the track day at Pocono has come and gone, and the problem did not resurface! Mission accomplished! Not sure what the ultimate reason was, though...I replaced the front bearings and races with brand new ones, properly lubricated and packed. I also cleaned the front brake calipers, checked the pads, and removed the brake shields. The brake calipers were badly gunked up, so a sticking piston under heat is entirely possible. Whatever it was, it appears to be gone!

BrucePigozzi

Well I guess new bearings are always nice. But what you described sounds exactly like what I got at Putnam Park during a DE. It turned out to be copious marbles on a hot day. I swore the bearings were going but it was gobs of tire affixed to one side more than the other. The cool down lap would fling much of it off and the trip home was fine. My fix was cheaper!