It is the Honda Drum Brake Wheel Cylinder on the rear of your vehicle that converts the hydraulic pressure produced by the master cylinder to mechanical motion. This is how the pressure the brake shoes apply to the drums is created on your Honda by using the movement inside of the drum brake wheel cylinders of its pistons.
The materials that the drum wheel cylinders are constructed of include mostly metal components but there are also two polymer seals. The seals are what keep the pressurized hydraulic fluid in place as the pistons move outward from the center of the drum brake wheel cylinder. After being used to create this seal for an extended period of time, the polymer seal in the Honda drum brake wheel cylinder will begin to crack and dry out. This is when the hydraulic fluid will begin to leak out of this closed loop system and cause a brake failure.
The driver of the Honda will notice an impairment to how the vehicle brakes when this occurs. When the inspection of the rear of the vehicle pinpoints a puddle of hydraulic fluid at the rear wheel the seals on the piston in the drum brake wheel cylinder will be the problem that has to be addressed.
The repair procedure is the same as a regular brake job with the inclusion of removing the drum brake wheel cylinder once the shoes and springs have been removed. Before removing the cylinder from the backing plate on the Honda, first break lose the brake line. This will be tough since the brake line has probably been in place for some time and but by the cylinder still being mounted, it will be held in place so the brake line nut can be broken lose and removed without damaging the brake line.