Why is the brake pedal hard to push or press? A hard brake pedal can be caused by several different factors. It can be as simple as the brake pedal getting caught on something to the power brake booster being bad. You could also have a brake pad or shoe that is sticking, causing the brake fluid to boil. When brake fluid boils, it expands and can cause the hard brake pedal that you feel. A brake pedal that is hard to press can also be caused by a build-up of water in the brake line. The water in the brake line lowers the boiling point of the brake fluid. A hard brake pedal can also be the result of a restriction in the brake line, such as a bent brake line or foreign material in the brake fluid. The most common cause of a hard brake pedal is the sticking brake pad or shoe, causing the brake fluid to boil. Tracking down what is causing the hard brake pedal can be frustrating, to say the least. Take the vehicle for a drive and when you come back, feel your brake lines near the wheels. Caution: The line may be very hot! If one is extremely hot, you may have just found the culprit causing the hard brake pedal.