It means your master cylinder needs to be replaced or rebuilt. The seals inside the cylinder can go bad and cause this to happen.
possible have a bad master cylinder
A symptom you almost always feel is a brake pedal that will not hold. You stop, hold the brake, and the pedal will slowly move toward the floor. This is a sure sign the master cylinder is bad. A leaking master cylinder or one that sticks, is also a sign is is defective. When you replace the master cylinder replace all the brake fluid in the brake system and bleed the brakes. Moisture in the brake fluid will destroy a master cylinder and this may be why it failed.Brake fluid leaking from the master cylinder. When you stop and hold your foot on the break the brake pedal will slowly go to the floor. Either of these symptoms means your master cylinder must be replaced.
a leak or a bad master cylinder
Usually the rubber seals go bad. On the other hand, if you live in a very humid area you might have a little water in the hyudraulic fluid and it could have rusted the master cylinder. They aren't usually terribly expensive to replace if you do it yourself.
Normally this is caused by a Master Cylinder that has failed. Replace the Master Cylinder. Normally this is caused by the loss of fluid in the brake system. The fluid reservoir needs to be checked first. It possibly may be caused by a bad master cylinder but the most common cause is loss of brake fluid.
First, make sure the master cylinder is filled with brake fluid. If it is low, there may be a leak somewhere in the brake lines or a brake cylinder. If the master cylinder is bad, you can normally pump the brakes up, but the pedal will slowly sink to the floor again. The master cylinder needs to be replaced or repaired.
What about the master cylinder? They go out, ha. That's all I can help you with though.
There is a smaller master cylinder next to the brake master cylinder. The clutch uses brake fluid also. If you mean where does it go if it is low, the slave cylinder on the transmission is probably leaking.
. If you have the 4-port master cylinder, the bottom ports go to the rear brakes & the upper side ports go to the front brakes.
Bad master cylinder or leaking line/caliper/cylinder
Usually when the break petal goes all the way to the floor, it indicates a leak in the break system. The most common causes are:no break fluid in the master cylinder due to a break line opening or a leaking valve in the master cylinder itself.if it is a power break system, then the vacuum assist may be leaking. There is a small (usually white) valve with a vacuum hose on it (about half inch) that tends to go bad and causes the petal to go down to the floor. Its typically an easy fix, an inexpensive.Good Luck.