Wheel Cylinder
Most vehicles today have braking systems that require the use of disc brakes in the front. This is the most modern system for braking and allows the vehicle’s front wheels to stop effectively when the brake pedal is pushed. On the rear wheels however, disc brakes are not used. Most vehicles have drum brakes. In order for drum brakes to work effectively, a wheel cylinder must be used on each wheel. The wheel cylinder pushes up against the brake shoes which resemble brake pads that are used on front wheels. The brake shoes then push up against the brake drum. This causes the friction that is needed to slow and eventually stop the vehicle.
A wheel cylinder is a part of a brake system that uses hydraulic fluid, typically oil. This hydraulic fluid is pushed through a tube that pushes against the pistons that are located inside the wheel cylinders. The wheel cylinders will push against the brake shoes at different pressures depending on how hard the brake pedal is pushed. This hydraulic brake system is very effective and gives drivers the power to easily control the pressure of the brakes and increase or decrease that pressure easily. The wheel cylinders are located on each rear wheel. Every wheel has its own wheel cylinder mounted inside the brake drum. The cylinders are located near the drum’s top on a fixed point that does not move or flex when the brakes are engaged. Wheel cylinders resemble tubes in shape and have pistons that are located on each side and protrude from the cylinder. The pistons travel into the cylinder and have rubber gaskets on them that help to eliminate the risk for hydraulic fluid leaks. Once the brakes are applied, the pistons are pushed outward from the wheel cylinder by the hydraulic fluid that is pushed through the tube in the cylinder. Once the fluid recedes or decreases back into the cylinder and the hydraulic brake lines, the pistons retreat as well and this releases the brake shoes from the drum and effectively releases the brakes on the vehicle.
Disc brakes use master cylinders to hold brake fluid. Wheel cylinders work in the same way although they are much more likely to wear out than a master cylinder. Wheel cylinders are not made nearly as strong as the master cylinder and must be replaced more often in order to have properly working brakes. Each wheel cylinder includes a bleed screw that is built into the cylinder. This bleed screw allows you to bleed the brake lines to remove air in the lines. Hydraulic brakes will not work properly if air is in the brake lines so they must be bled using the bleed screw anytime the brakes are replaced. Wheel cylinders do begin to leak fluid after a period of time and should be replaced regularly. It is important to know when your brakes are due to be replaced. This is typically done after a specified number of miles are driven or after a specified period of time. If you are unsure of when to replace your brakes, check with your local mechanic. You can have your brakes inspected regularly to know for certain when they need to be replaced. If a wheel cylinder begins leaking and is not replaced it can cause damage to your brake shoes requiring them to be replaced as well.
It is also possible to rebuild a leaky wheel cylinder, depending on the severity of the leak or damage. Rebuilding is much less expensive and is not always possible. If the bleeder screw is deteriorated to a point that prevents you from opening it to bleed the brake lines, then replacing the wheel cylinder is the only choice. Replacing is also much faster. Rebuilding takes about twice as long as replacing the wheel cylinder and may simply not always be the best choice.
