Air in the brake system. You need to bleed the air out of the system.
The power brake booster is failing.
This is because of the antilock brake systems, or ABS. When the ABS is activated in a vehicle it can feel like the pedal is pushing back at you when you stop or start to slowly press the brakes.
The brake pedal vibrates.
Press down on the parking brake lever until you feel it click. This releases the pedal and it will come up all the way.
Typically, that comes from having air in the lines.
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.
It seems like there might be air in your brake system. You should try bleeding your brakes and filling it with fresh brake fluid.
To check if the power brake booster is functioning properly, start the vehicle and press the brake pedal several times to deplete any vacuum in the booster. Then, with the engine running, press the brake pedal; it should feel firm and then sink slightly as the booster activates. Additionally, listen for any hissing sounds that might indicate a vacuum leak, and inspect for any visible cracks or damage to the booster. If the pedal remains hard or the vehicle requires excessive force to brake, the booster may be faulty.
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brek pads