My front brakes in my 1988 Mazda MX-6 were completely redone brand new by a trustworthy mechanic 9 months ago, but have been squealing everyday really bad. The steering wheel shakes sometimes when I stop at high speeds and the car seems to be working hard. Today the brake pedal hit the floor a few times and felt like I almost lost my brakes. I brought it into a new mechanic who said it might be the brake master cylinder. Is this a possibility and what can I expect to pay for this job?
squeaing/pedal to the floor/engine working hard/steering wheel shake = no relation to each other whatsoever. You have several issues here. Brakes are the first priority. The pedal going to the floor may very well be the master cylinder, it could also be air in your brake lines; I would try bleeding the brakes first. The squealing is almost always due to the trustworthy mechanic not using anti-squeal on the back of the pads when he/she installed them. A tube of the stuff is about $3 and is enough for about 10 cars. I’ll let someone else address the shaking/engine working hard.
I think its all due to one thing, your caliper bushings are stuck. The squealing noise is due to what alex said, but the rest can be caused by sticking caliper bushings (aka caliper pins).
If the squealing is a new noise and did not occur just after the brake job, then it too is due to the caliper bushings, and at this point, your brakes could be VERY dangerous. Someone needs to pull the wheels and inspect the brakes because I suspect your rotors are about cut in half.