[mattsauto]

I'm working on a 94 850. It recently had brake pads installed, but the shop/individual did not turn the rotors. When I got it, the rotors were severely warped (all 4). I had the rotors turned, but this didn't help. Now the whole car shakes violently when you brake hard. I can't isolate whether it originates from the front or back. One suggestion has been made that it could be brake booster. My initial thought is the ABS hydro unit. Brake fluid is pristine. Any ideas?
Thanks,
Matt

 

[mattsauto]

Understood. This just seems to be much more than mere warped rotors. This is violent shaking of the whole car. It's not magnified in the steering wheel as one would expect from a warped rotor, this is "shake your liver" kinda stuff. You can feel the pulse in the pedal, when the pedal pulses up is when the car dives like in a hard stop. I just remembered, I rotated the tires when I checked the brakes, but it drives/handles great until you hit the brake pedal.

 

[mattsauto]

I did find that the rotors were warped. You were correct about resurfacing a warped a rotor. It didn't help. With that said, while working through the process, I replaced all 4 rotors and found the right front caliper was sticking open, barely contacting the warped rotor, but the rotor was warped so bad that I believe this side was causing a lot of the pulsing. As for the shop, I think they just need a new brake lathe. They've turned rotors and drums for me before with no issues. I didn't look twice at these, but should have. It was obvious that these rotors should have been replaced from the beginning. Lessons learned. Thanks for advice and the link is excellent!