The most common reason this happens is because you have a leak in one of your lines.
Why do my brakes go to the floor when i start my car.
Also if a leak occurs in the system it will be unable to build pressure due to the lack of fluid causing the brake peddle to travel to the floor which can be followed by the brake system.
If the brake shoes are worn the air gap between the shoe and the drum will be enlarged making the brake pedal travel downward beyond its normal throw.
One of the reasons is the brake system loses pressure from an external brake fluid leak.
Another common reason why your brake pedal may go down to the floor is because you are running low on brake fluid.
When you are ready to leave for work after your car has sat for a prolonged period of time check the ground underneath your car for puddles.
If you step on the brake pedal and it has little to no pressure and goes all the way to the floor especially if you re getting no braking.
Check your brake fluid.
Pressure on the brake fluid cases the brakes to be applied to the wheels.
If it s low top it off to the mark on the side of the reservoir.
If your master cylinder doesn t work properly or only works sometimes you re going to lose braking power and occasionally your brake pedal will go all the way to the floor.
The leak may coming from a brake line or one of the brake calipers.
Check brake shoes in case your car has a drum brake system after the above most common reasons for brake pedal goes to floor check your car s rear brake shoes.
1 leak from brake line or brake caliper.
A bad brake booster.
Technically there are two main causes that would make the brake pedal sink all the way to the floor.
Low brake fluid level.
The brake system in your car is a sealed hydraulic system and relies on close tolerances between the brake pads and rotors or the brake shoes and drums.