You may have problems with your brakes' master cylinder. Have it checked by a mechanic.
How to change brake lines on a 1991 Buick Lesabre?
Dot 3
Small pedal on the left of the brake pedal - activates the rear brake to hold vehicle
press back down on the pedal
Cut the wire
Should have an access panel inside trunk
carb cleaner or brake parts cleaner
5/16" allen
33 Ft lbs
You may have a vacuum leak at the brake booster. Have the brake booster inspected.
Book time for replacing brake booster 2.6 hrs
I think the light assembly screws out from the inside of the trunk.