Bizzles80

Hey all, I'm hoping for a little wisdom from the internets here as my indie is at a bit of a loss as to what the issue is. I have a '10 997.2 C2, manual trans, 80k miles. Here is the situation...

It started at a HPDE event in the spring. Had the car on the track for the first run. Everything felt good the first couple laps, then I go into a turn and it feels like a tire is rubbing or something. Not constant, but intermittent tugs on the steering wheel. I backed off, waved everyone by, limped in about 50% speed with "tire rubbing" sensation at the turns. Get off the track, immediately see my mechanic, he jumps in and can't get it to reproduce at low speeds in paddock. No signs of any tires rubbing. He checks the power steering fluid and it is black (burnt). Says he's never seen that on 997 before. Suggests to go back out next run at back of pack, see if it's still happening, and report back. Second time out, couple laps in with everything normal and get up to temp, and problem comes back. I limp off, go back to mechanic, he suggests power steering pump or rack issue. Suggests replacing pump first to see if it fixes it.

After the pump was replaced I took it out for a drive once. I got it warmed up on the highway and then got on a 55 mph country road by my house that has some 35 mph turns that are much funner at 55. On the first 35 mph turn, I got some kind of mechanical grind/hum/bit of vibration in the floor boards, along with the tire rubbing feeling from before. It did not feel very good! I took the 2nd turn at a little less speed and got the same feeling so shut it down, limped it home, and brought it back to the mechanic. This time to replace the rack. (I would also say, after the pump was done, it had a bit of a floaty feel on the highway in a straight line (not sure if it was doing this originally, as I wasn't really paying that much attention then). It was very subtle, and maybe I was being too critical, but the steering is normally very precise. It felt that while the wheel was straight, all of a sudden it would move about a degree or two off. Nothing major, but did not have the normal steering feeling. There would be occasional moments where is would just drift a bit for no reason.)

Since the rack has been replaced, I have spent a bit more time driving it. The "tire rub" sensation happened once the first time out, but not since. Now on higher speed turns I get a vibration in the steering wheel and a clicking or knocking sound, that at first seemed to come from steering column, but now seems to be in front end. This happens at not too dissimilar times as when the "tire rub" sensation would occur. Easy enough to get it to reproduce, as long as I can find an empty road to swerve back and forth on at 40+ mph.

Does anyone have any input or suggestions as to what might be the issue? He did put a rebuilt rack in. Not sure if that could be a problem, but worth noting.

Thanks, Jeff

Iceter

Thinking out loud here--maybe wheel bearing(s), a tire de-laminating, something else loose or perished in the suspension that is allowing one or both front wheels to not track correctly when that particular component is loaded?

Did the mechanic check everything else under there while he was replacing the PS pump and then the rack?

Bruce In Philly

2009 C2S 158K miles

Regarding the black fluid... normal and not evidence of a problem. IMO, we should be flushing our power steering system out... I dunno, maybe every 75K miles?? Black fluid can't be good. See my DIY for the color of my fluid. The fluid in this pic is maybe 75K miles old as I had a leak where the tank attached to the pump... and most had drained out. Fresh fluid is minty green. See the fluid color here: https://rennlist.com/forums/997-foru...ement-diy.html

You may be experiencing a bad bearing in a wheel. These big bearings don't fail the same way as in my other cars. Jack up your car, grab the wheel and drive to move it back and forth.... if the bearing is bad, you may experience some play. Another give away, is the bearing (usually) will make the sound in only one direction of turn... when the system is loaded up only one way. So either left handers or right handers will make the sound but not both.

Got to ask: Are you tire sizes Porsche approved as in your manual? Are you on Porsche rims?

Keep us informed.

Peace
Bruce in Philly

Bizzles80

Yes, said he gave it a good look. He is the best indie in town and recommended by everyone here. I've been going to him for 4 years. Said he also replace the tops of something (suspension related?) while he was in there, but it didn't end up on invoice so not 100% what that was. Front tires in good condition, rears brand new.

Bizzles80

Hmmm, interesting that power steering system may have never been the issue. Yes, original Porsche wheels and approved tire size.

Originally thought this was only happening on left hand turns, but can reproduce turning either way now. Would bearing only be issue at higher speeds? Does not occur unless under pressure.

Bizzles80

Only suspension related modification done has been H & R lowering springs 4 years ago when I got it. Thought I would throw that out there.

Also @Bruce In Philly I will jack it up and check on any play.

Bizzles80

So, in regards to any play in the front wheels. I jacked it up and, comparing to the rears which are completely solid, there is a hair of movement back and forth in the front. Just a hair. I'm not sure what an acceptable amount would be, but this is not much. Both fronts have the same amount of minimal play in them.

BLU997

Wondering if the noise rises and falls with RPM?

Burnt oil implicates working pressure is escaping through an orifice/bleed/relief/valving/control/internal leak/exess clearances.

Excess oil passing when it shouldn't, causes the temperature to increase, lowering viscosity, encouraging more internal leakage.

Phrog Phlyer

Maybe you have a wheel speed sensor going bad and the stability management system is kicking in.

Bizzles80

No, it's consistent noise for short period. Only when under load.

Bizzles80

No dash lights on. It sounds like with speed sensor there would be some warning lights.

Petza914

When checking for front wheel play, you have to make sure the little bit of wiggle isn't the rack moving a bit wherebrhe DS wheel is moving the same amount as the PA wheel you're pulling on or vice versa. Aside from wheel bearings, if also check the bushings in the Lower Control Arms as those can result in a clunk when they load or unload.

Spiffyjiff

when the "rubbing" sensation starts, is it just after hitting curbing (on track) or medium sizes bumps/road imperfections?

Bizzles80

Ha! No, just in smooth, higher speed turns. Getting together with indie again next week to look further into it.