Two problems related to brake disc caliper have been reported for the 1998 Buick Regal. The most recently reported issues are listed below.
When applying brakes, brake caliper fell off, jamming front wheel causing it to freeze, resulting in loss of control. The vehicle would drive in reverse but the right front wheel stayed locked. The cause was found to be two bolts that hold the caliper sheared off. The caliper, after coming off, jammed the front wheel movement to halt. The vehicle shaked when backing and turning due to power steering gear failure. The brakes pulsate when applied due to excess runout of brake rotors.
Severe front brake problem with shake and possible rotor damage reported to and repaired by cavender Buick, under warranty, on June 1999. (note: your NHTSA site has several complaint entries regarding same). On 12/25/00, on return trip traveling i37 north to san antonio from corpus christi, I applied brakes to make my exit on san antonio loop 410. Immediately after releasing the brake we heard a loud rotating clunk from the front end. I pulled over to the shoulder. I was on the shoulder when the car movement froze and came to a jolting halt. This was at 1630 hrs. Tow truck arrived at 2200 and moved car to nearest gm dealership which was cavender Oldsmobile. Although cavender dealerships are family related they are 2 totally separate dealerships at different locations. They serviced my car the following day and determined that the right front brake caliper had sheared off and jammed somewhere between the rotating wheel and the fixed axle preventing foward movement on the car. Interstate 37 was wet and slick on Dec 25th and I am very very happy that the calipers did not come off while I was traveling the speed limit on that freeway. Otherwise I could have checked off "yes" on your fatality box on this form. It is upsetting to know that you have at this site information regarding problems with the brake system on this vehicle yet they are under "complaints" while you have windshield wipers under "investigations". I would then suggest, with strong urgency, that an immediate investigation be initiated regarding the serious problem with the brake system, design, or materiels used. The shaking maybe causing stress on the bolts that hold the calipers.