I have a light vibration that happens at highway speeds, but doesn't always happen. It seems like 3/4ths of the time I'm on the highway I get vibrations if I'm over 65/70 mph. It seems to happen most of the time on the highway, but it will also randomly drives smoothly.
I've had a lot of things happen lately with my car, a 2003 Buick Century, so I'm not sure what the cause would be.
In January I replaced my front pads and rotors. The car drove well, but when driving around a 45 or 55mph turn at regular highway speed, it made a funny noise, and after that vibrated at highway speed. I replaced a very rusty brake caliper that I suspected when I changed the rotors and the problem went away. This was at ~102-103k miles.
In February, my car was parked on a street that flooded at night. My passenger side was wet on the inside. I assumed the wheels got underwater too.
After ~4/15 I noticed my rear brakes squeaking a lot, and I noticed a light vibration that I think was at any speed. I also got a transmission fluid leak, and assumed it might be related to the vibration. I didn't have much free time, so over the next month I replaced everything in the rear drums - shoes, rotors, springs, wheel cylinders, some rusted/stripped bolts and the metal part of the brake line. I also rotated the tires. After doing this and test driving on the highway, I noticed the vibration was worse & now it only seemed noticeable at highway speeds. I thought the vibration was coming from the front though, and the steering wheel shook a little.
After that, I brought the car in to have the transmission fluid flushed and have the transmission checked out. Nothing looked bad other than a minor leak. Afterwards, the car still vibrated the same way.
So, at 105k miles, I replaced a pair of tires and got an alignment. I had bought the car at 20k miles with 4 good tires and replaced a pair at 80k, so I was due to replace the last 2 tires anyways. Afterwards, the vibration was much less noticeable, but still definitely there. I also noticed that anytime I stepped on the brakes going highways speeds, the brake pedal pulsates. I'm not sure if that was there before or was new. Stepping on the brake below around 50mph, and there is no vibration.
I'm not sure what it could be. It's weird that it feels like it's coming from the front, and that I had a vibration there before. Maybe it's the other front caliper is going bad? It's also strange it doesn't always happen, it's like something is loose, but everything is torqued correctly AFAIK. Could the brake pedal pulsating be a different issue? I also suspect the wheel bearing, because looking back, I think it could have been flooded. Any ideas where to start? Are there any tests I can do?
Right now, my plan is to drive it 70mph and brake without gripping the steering wheel to see if it pulls to any side. I also plan to jack the car up to see if the wheels, especially the passenger side, have any give to test the wheel bearing.
Thanks in advance for any help.