Hello,
After browsing the forums a bit I decided to see if anyone can help me. I saw some threads here that sounded similar to the problem I am having but without answers. Figured I would try my luck.
Background: 2006 Grand Prix with the V6 and 71000 miles.
Two days ago while driving on my daily commute home (highway) the car began vibrating through the steering wheel with increasing intensity. I pulled over and the vibration increased under braking. I inspected the car and checked the lug nuts for all wheels and all were tight. I got back up to speed and subsequently had no problems other than a marked increase in brake pedal pressure (ie, travel distance was shorter than normal). After some city driving the pressure seemed to normalize. The next day the same thing happened, but only on my commute home (to work was not a problem). Pulled over, got back on the highway, no problems. However driving in the neighborhood I could hear a rhythmic, subtle clicking noise coming from the drivers side front wheel, while going straight. I tested the brakes and the brakes seemed strong and were not wobbling under braking. The car has had recent alignment and tracks straight. I checked the drivers side wheel at 12' and 6' oclock and there was play in the wheel.
I took it into the shop reporting these symptoms, hypothesizing that there was a bearing or brake rotar problem. The mechanic was not able to reproduce the symptoms but reported a leak in the power steering pressure hose, a small leak in the transmission coolant hose (I believe that is what he said) and a poor bearing in the drivers side front wheel. I had recently checked all fluids and added a little power steering fluid, so I thought there might be a slight leak but I haven't had any power steering symptoms that I know of. He also claimed the brakes were "good". I had the mechanic replace the bearing and rotate the tires (i noticed my driver side front tire had a little more wear on the outside edge, maybe that is a sign?), hoping that would do the trick. I took the car home and added Lucas Stop Leak to the power steering. I siphoned out 1/2 the power steering fluid to see that it was dark, which I have been told is not a great sign.
Anyway, thought the problem was solved. Couldn't find any obvious leaks myself (although I didn't put it on jacks). Went to drive and got up to 40 mph and the same problem started again with a noticeable change in brake pressure that was intermittent and a rhythmic click coming from the drivers side front wheel. However, both issues resolved themselves after a 20 minute drive on the highway and subsequent city driving.
At this point I feel like I suspect a) something wrong with the brake pressure and possibly a warped rotar, b)damaged CV joint, or c) damaged rack and pinion. I assume the tie rod is good, although my mechanic may have missed it. The only other thing that I would mention is that at low speeds and typically when I first start the car I can hear a scraping/shaking sound underneath the drivers compartment that I guessed was a lose exhaust cover, but may be something else?
tl;dr: Car has intermittent shaking on highway, has intermittent clicking coming from the front wheel while going straight, just had a bearing replaced, and possibly has a power steering leak.
Thank you for any help you may offer!
Edit: also wanted to note that this model does not have ABS or TC
