Usually when a brake pedal feels more stiff than usual, there is a vacuum leak. The brake lines probably should be bled.
The brake pedal vibrates.
The power brake booster is failing.
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.
Adjust or replace the stoplight switch at the upper end of the brake pedal under dash area
Get some speed up, then brake hard. If you feel the brake pedal pulsating you have ABS:
Hardness in the brake pedal can because by low brake fluid. Air in the brake lines can also cause the pedal to push hard.
Yes, you will feel the brake pulsate. Just keep full steady pressure on the pedal and steer around the accident if possible.
Probably the brake booster going bad.
Any time the brake pedal is hard to press then you need to check and see if the brake booster is functioning properly.
brake switch located on the top of the brake pedal
easiest way to test vacuum pump is , with engine off, pump brake pedal until pedal goes hard keep pressure on brake pedal and start engine if vacuum pump is good, you will feel the brake pedal go softer so you don't have to use as much effort for pedal to be depressed
you will have a hard brake pedal