97 850GLT wierd brake issue

[justin_in_dc]

Hopefully someone here can help to diagnose my girlfriend's Volvo's problem. I've tried searching for it, but no luck so far.

Here's the deal. When braking to a stop, the car stops smoothly and effectively when the pedal is pressed square on. No vibration, no grabbing, no symptoms of anything wrong.
However, when the pedal is not pressed square on, as in pressure being applied to a corner of the pedal, the whole car vibrates and groans as it comes to a stop. I didn't believe my g/f when she first told me about the problem because it just didn't seem possible with a hydraulic system to be affected by the part of the pedal that is pressed. But I tested it myself and sure enough, when the side or corner of the pedal is pressed, the car vibrates and groans from about 25mph down to 5mph.

Because of the wierd situation this occurs in, I am at a loss. Has anyone experienced this problem before?

Any help is greatly appreciated!

[DCintraining]

Sounds very weird to me! Just an idea, put your hand on the pedal and see if you can shake it side-to-side, if you get a good deal of lateral movement then 1. check to see if the fasteners attaching the pedal to the chassis are loose and 2. check to see if there is a problem with the pedal linkage to the piston arm for the master cylinder. If anything is loose or bent then you may have your problem. Mechanically speaking if your master cylinder is starting to wear and there is unequal pressure is applied to to the break lines you could get vibration and braking issues. I barely passed physics, so these are just ideas.

Eoin