Have a rattle underneath my 1992 buick roadmaster when you are on rough road - I have checked for something loose, brakes,tailpipes,park brake cable,mufflers, linkage on transmission,swaybar,ball joint, tierod,pittman arm,a-frame bushings, univeral joint - do you have any other suggestion?

There should be a release handle at the lower end of the dashboard immediately above the pedal used to set the brake. Pulling out on this handle will release the brake. Note that it may be 'faired in' to the dash, possibly appearing as a small panel, but should have an opening along the bottom to insert your fingers into.

check the vaccum hoses on the booster

sometimes the other switch is to cut out the cruise control when the brake is applied. I would more suspect something in the fuel injection controls such as a mass air flow sensor or throttle "switch." your car is probably too old to have an auxiliary air bypass valve but if it has one look at it as well. good luck

Ive owned many of these, Id check for a Lose calliper or worn out brake pads , wore out ball joint ,, then look at the power steering tie rods,, then if nothing wrong there check to see if there's a broken coil, had the last one happen to thought it was the brakes, but was a broken coil and the rubber fell out at the top of it so was steel on steel, and finally check the front sway bar bushings these break too, Sorry to list so many different things but Ive ran into a lot of bugs over the years with my Impalas caprices and Road masters.. Hope this helps.. And feel free to ask me anything about these cars, ive owned over 10 of them.. and I am sure had everything you could think of happen :)

If it pulls to the left,then the right side is not applying
equal pressure.

What if you command the abs open & drive with scan
tool

did you check the brake switch underneath the brake pedal?

is it drum brakes in the rear or disc?. it could be that it needs to be bleed out or a bad master cylinder/or the wheel cylinders or slides are seized up .if you need any further insistence feel free to ask again thank you .

hi i have just had this same thing happen please help me also a 92 roadmaster

SOMETIMES A BROKEN SPRING OF THE BRAKE SYSTEM CAUSE A SIMILAR NOISE

this is a common problem with all GM cars.

It is not your fuse or the power, it is in the column.

Pull the removable cover from under the dash to expose the column,
you will see a long plug with a crazy amount of wires going into it.
pull the plug out, and make sure there is no debre in the plug, or dried out grease.
while your looking make sure no wires are burnt, singed or cracked.

If this does not work, then you may have to take it in to have the wheel pulled so the components and wires can be chacked in the column.

Note:
If you can shift the car out of park without pushing on the brake, this is definatly your problem.