As the name suggests, the Buick drum brake wheel cylinder is used on drum brakes that today can only be found on the rear of your car. There are two drum brake wheel cylinders on a Buick, one near each of the rear wheels on the brake backing plates mounted on the rear end. The drum brake wheel cylinder is the part that applies the pressure to the shoes of the braking system in the drums. It is similar to the brake calipers as compared to its function, but not in its appearance. The hydraulic fluid enters the drum brake wheel cylinder and pushes out against two pistons that are situated at opposing ends of the cylinders. There are also two rubber grommets or seals that help to trap the brake fluid in the brake system on the outside of the pistons in the cylinder. It is these seals that are the most common culprits to the drum brake wheel cylinders needing to be replaced. When brake fluid is noticed on or near the rear wheel of your Buick, this is generally the source. Today most of the Buick drum brake wheel cylinders are replaced with rebuilt parts by your technician. The rebuilt parts are reconditioned at an alternate shop and not performed at the time of the brake job on your vehicle. This is the most common practice so the time required to complete the brake job on your car is the smallest allotment possible. Time saving processes like this is why a brake job on your Buick and most other makes of cars can be completed in an hour or less. This way your car can be out of the shop and back with you at the wheel as quickly as possible so you can travel to your destination in a safe and effective manner.