Brake Master Cylinder

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Given that the master cylinder will wear through normal use and can become corroded over time, its essential to replace it in order to avoid the risk of brake failure. A vital part of your cars braking system, the master cylinder converts the pressure created by your foot pressing down on the brake pedal into hydraulic pressure, which builds up as brake fluid becomes trapped. This hydraulic pressure sets the whole braking mechanism into action, ending with the wheel cylinders demobilising the wheels. The master cylinder is a complicated piece of machinery, itself having several components. These include the housing, bore, brake fluid reservoir, fluid level sensor, piston(s), rubber cap, return spring and, in a manual car, rubber boot. Hydraulic pressure is instigated when the spring, cup and pistons slide in the cylinder bore. As an extra safety measure, modern vehicles usually have dual master cylinders, each with a different system of brake-circuit operation. If one cylinder fails (perhaps through the loss of brake fluid), the other will be able to work alone until the malfunctioning cylinder can be replaced. A common cause of failure is contamination or loss of brake fluid; if brake fluid becomes hygroscopic (attracting water), it will affect the system.

When you step on the brake pedal in a vehicle to slow it down, its braking system uses a brake master cylinder to convert the pressure you place on the pedal into hydraulic pressure. The conversion of the pressure takes place because the brake master cylinder transfers brake fluid to the braking circuit as you step on the brake pedal. The brake master cylinder will do this no matter if your vehicle is using disc brakes or drum brakes. There is no way any braking system could exist without a brake master cylinder. Warning Light The first symptom that is the easiest to notice is when the Brake Warning Light illuminates on the dashboard. This indicates that there is problem with the braking system, so it might not necessarily mean that the brake master cylinder is at fault. But if the braking system sensors detect the brake fluid pressure is dropping, it will likely be due to a bad brake master cylinder. This will result in the warning light coming on. Leaky Brake Fluid The brake master cylinder needs a certain level of braking fluid to create the hydraulic pressure necessary for slowing down the vehicle. If the brake master cylinder is leaking braking fluid or if there are unsecured reservoirs on the cylinder which are holding the fluid, then you will have a low brake fluid level for sure. This will impair your ability to slow down the vehicle. You would need to replace the brake master cylinder in this situation. Spongy Brake Pedal When the brake pedal starts to feel spongy as you place pressure on it with your foot, this will automatically be a sign that your brake master cylinder is having issues. The cylinder contains rubber seals which keep the brake fluid inside of it. If these rubber seals were to get worn out or damaged, then there will be an internal brake fluid leak. The result of this would be a spongy feeling in the brake pedal. Contaminated Brake Fluid. Another problem that could happen as a result of worn out rubber seals is contamination in the brake fluid. The seals not only help keep the brake fluid from coming out, they also prevent dirt and debris from mixing with the brake fluid. If this were to happen, the brake pressure would not be as strong as you step on the brake pedal. You'd probably end up pressing down harder on the pedal just to get the vehicle to slow down like normal. Sinking Brake Pedal. Following all these other symptoms, you will start noticing the brake pedal not returning to the top after you have removed your foot from it. Instead, it will slowly sink to the floor. This could become a real driving hazard, so you wll want to fix the brake master cylinder right away at this point.