The most common symptom of a master cylinder that has failed is that when you stop and hold your foot on the brake pedal it will slowly fall to the floor. This is called pedal fade and means the seals within the master cylinder are leaking. If you push the brake pedal and it does not return it may be defective. You may also see a leak at the master cylinder.
Master cylinder empty (no brake fluid) Leak in brake line or wheel cylinder Defective 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.
If the Master Cylinder is defective then replace it.
Master cylinder is defective. Replace it.
Logically if the Master Cylinder keeps failing there are only a certain amount of things coming into play here. Either you are buying defective products or the brake fluid is contaminated and causing the Master Cylinder to fail prematurely. Let's start with the Master Cylinders you are installing. I will not name suppliers but not all Master Cylinders are created equal. Some rebuilt Master Cylinders are defective right out of the box. I suggest you buy a NEW master cylinder. Before installing the new Master Cylinder flush all old brake fluid out of the entire system, install a new master cylinder and install fresh fluid from an unopened can. With a new master cylinder and fresh clean fluid, you should have no future problems.
Defective master cylinder, low of fluid, or leak somewhere else in the system.
Low fluid level or defective master cylinder.
I would suspect a defective Master Cylinder. Fluid leak.
There is still no fluid pressure. Make sure that the master cylinder was bled as well as the wheel cylinders. New master cylinders can be tough to bleed all of the air out. The new master could be defective.
Yes, it can also be a defective master cylinder.
Contaminated brake fluid? Frozen calipers? Defective master cylinder? Master cylinder activation rod not adjusted properly?