Low fluid or something is wrong with your power assist (booster). Having it vacum tested could be a good idea.
The Booster only works when the engine is running and a few seconds up to half a minute after it has been turned off.
hard brake pedal is the most obvious sign only way i know to test a booster, is to turn engine off. use brakes several times till pedal is hard. then with brake applied,start engine. the brake pedal should then soften.if the pedal stays hard the booster is bad
Hardness in the brake pedal can because by low brake fluid. Air in the brake lines can also cause the pedal to push hard.
Push hard on the brake pedal when your moving. If the wheels start to lockup ABS will be activated.
The brake pedal vibrates.
power booster behind master cylinder sounds like they may be the problem
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.
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
Most likely your brake light switch is either not adjusted properly or malfunctioning. It is located under the dash and the brake pedal will press it when it is applied. They are not hard to adjust or replace.
you will have a hard brake pedal
The power brake booster is failing.