- Cup seals and bore damage, due to neglected fluid maintenance schedules.
- Fluid contamination or incompatible brake fluid use-which causes seal and bore damage and could result in complete hydraulic system failure.
Customer does not bench bleed the master cylinder causing the introduction of air into system which in turn causes a spongy pedal.
Master cylinders are made of cast iron or aluminum and are mounted near or on the rear engine cowl (commonly referred to as the firewall) where it is typically easy to inspect and repair them. The effect of water and dirt is also minimized at this location. They are normally provided with plastic reservoirs for brake fluid to maintain the proper level of brake fluid in the brake system. Electronic sensors within most master cylinders monitor the level of the fluid in these reservoirs.
- Removes air from the lines that could cause a soft pedal (air is compressible while hydraulic fluid is not).
- Replaces the old moisture-contaminated brake fluid with fresh, clean Fluid. After several years of service, brake fluid is often saturated with water. As the moisture content goes up, the fluid's boiling temperature goes down. This increases the risk of fluid boil and causes loss of brake pedal under severe operating conditions.
- The brake fluid specified from the factory must be used (DOT 3, 4 or 5). Note: DOT4 fluid can be used in applications calling for DOT 3 fluid, but DOT 3 cannot be used in applications calling for DOT 4. DOT 5 is not compatible with DOT 3 or 4.
The master cylinder converts the mechanical force from the brake pedal into hydraulic pressure. When the brake pedal is depressed, the master cylinder piston moves forward and pushes the brake fluid ahead of it. Since the brake lines and wheel cylinders are filled with brake fluid, the piston acts on a solid column of fluid.