There are either two or four Jeep drum brake wheel cylinders on your vehicle. They can be found mounted at the top center section of the backing plates of the drum braking system. This is the braking component that performs a similar function as the brake caliper. The failure of the drum brake wheel cylinder is rare but does occur since there is a pair of seals holding the hydraulic fluid in place on your Jeep. They can be seen when the pins connecting the drum brake wheel cylinders to the drum brake shoes are removed. This is the only place where fluid can leak from behind the brake drum. If this occurs, a puddle of clear thin brake fluid will appear on the brake shoes and on the pavement when your Jeep is parked. The driver can also notice a softness in the brake pedal when it is being depressed. This softness is the fluid leaking out of the otherwise closed loop system past the seals in the drum brake wheel cylinder. This is a good indication that the seals or the cylinder must be replaced. The replacing of the Jeep drum brake wheel cylinder is done by removing the shoes from the backing plate first, then disconnecting the brake line. This line might be fused to the cylinder due to the time it has been attached. This is the reason for leaving the cylinder bolted to the backing plate when removing the brake line. Once the line is removed the drum brake wheel cylinder can be unbolted and removed. Because the cylinder is part of the closed loop hydraulic system, the air must be removed once the new braking component on your Jeep is put into place. This is done with the drum brake assembly put back into place and pressure applied to the system. The nipple on the cylinder is then opened allowing the air to escape.