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I am troubleshooting a small vibration and looking for any suggestions people may have to offer.
2010 C2 with 85,000 miles
Steering wheel starts to vibrate very slightly at ~50 mph. At this speed it's barely noticeable. As speed increases into the 70's it gets more amplified but placing my hands on the steering wheel will dampen it, although I can still feel some vibration in the car. Going faster than the speed limits (on a track) doesn't seem to make it any worse than the highway speeds but I haven't done extensive testing at those speeds.
It seems like the vibration level is different at different times, like cold tires vs. warm tires but it's hard to tell. Warm tires appears worse.
Kicking it out of gear and coasting at speed does not change the vibration even if I race the engine rpm's while doing so.
This occurs on two sets of wheels/tires, including brand new from Tire Rack and new tires were re-checked with road force balance so I'm ruling out wheels/tires at this point.
There is no perceptible play in the steering and no noise at all when turning left or right.
Checked all the front steering linkages and don't find any play at all in tie rod ends etc. I cannot see the tie-rod inner but can't find any play by feel.
I've checked with different tire pressures and this doesn't seem to change it much if at all.
Indy, who is a Porsche specialist, believes the problem is a bad steering rack. I'm trying to figure out how to positively diagnose this before spending the significant amount it will cost to change out to a rebuilt rack. I've not found many rack failures with the 997 racks (without fluid leaking) and I wonder what part of the rack could have failed without any other signs like noise, gear lash or fluid leaks.
Does anyone have suggestions for other possible causes.
Here are two ideas I have so far:
1. Steering rack mount bushings worn causing a very small vibration which amplifies up the steering column. Again, the vibration is small, but annoying. Not sure what would wear out in 4 years of highway driving.
2. Alignment is off slightly. This is a new car to me so I don't know the history other than it seems to be a well maintained 4 year old car. Servicing dealer looked at the history and didn't find any complaints or repairs in the steering.
3. Car hit a curb and bent something I cannot see.
The car idles rougher than I would expect but I don't think this is related. That could be engine mounts?
I appreciate any advice this great community can offer.
Same vibration with different wheels rules out wheels. Steering rack is a real long shot. At this point though everything is a bit of a long shot. But throwing parts at a problem seldom works, and …. steering rack? Come on.
I would check the other spinning masses. Jack the car, pull wheels, get a rotor spinning, see if you feel anything. Rock in the rotor? Damaged hub?
It is most likely a bent rim (or lower control arm).. balancing wont address this.... you must look specifically for a bend. This stupid and performance-reducing fashion of bigger rims and rubber band tires is just a recepie for this sort of thing.
Given you mileage, the other high-probable item is the lower control arms... the lowest ones with three connection points. My buddy had a vibration (2009 c2 just 30K miles) .... I suspected a bent rim.... it was this lower control arm. That arm is a common wear item. He swapped it out and problem solved.
These cars go through control arms way more often than we change them... they become the source of gremlins, noises, vague handling, and vibrations. The challenge is they start failing when new and the effect is gradual so we don't notice them like a pump failure. Unless they leak goo, it is very very difficult to see if one is failing. The center bushing has openings through it and will tear there but unless it is really bad, you most likely will not see it. These bushing are designed to handle pretty big loads so just looking at them or twisting with a pry bar will not always present the offender. I found tears in my rear ones but I had to remove the shocks to see and even then it was tough. I had no idea they were bad as I was replacing leaky shocks. When I put the new ones on, the car was way more planted.... I had no idea my handling had been dripping away.
If I had the money (I definitely have the neurosis), I would change all arms every 50K miles.
Thanks for the suggestions! I will remove the wheels again and see if I can identify any bushing tears without total disassembly requiring an alignment. It looks like replacement bushings are available from Elephant racing and probably others.
Brake pads are brand new and I can't feel any pulsing when braking so I don't think it's rotors. Hub damage is another area I need to confirm. I'm cautiously optimistic to hear others dubious about a steering rack problem but I'm not ruling it out. At least I'm not crazy to question it.
I just went through a similar issue caused by wheel spacers in the front. If you have spacers that are less than 10mm they most likely don't have a "flange" that mimics the hub. It is easy to mount the wheel off center without the flange. Pull the center cap off of the wheel and pay extreme attention to the space between the wheel and the flange of the hub. This is an inexpensive item to check. Good luck
Final solution: After living with this vibration for a year, and it would change a bit from day to day, I finally had a front wheel bearing replaced and the vibration is gone. I'm glad I didn't mess with the power steering rack.
12-30-2015, 09:03 AM
997.2 Steering vibration
