The material that composes the Isuzu Disc Brake Pads allows for it to slowly disintegrate when friction is created in the braking action on your vehicle. This disintegration of the disc brake pads can be seen in the dust that is generated by your Isuzu braking system.
There are two Isuzu disc brake pads on each front brake wheel assembly on your vehicle. They are on opposing sides of the disc so they can be even squeezed by the disc brake caliper in the braking action. When the disc is smooth and flat, the friction created slows the vehicle down and the disc brake pads slowing wear and turn to a fine dust.
As the pads lose their composite material and turn to dust over time and repeated use in the braking process of your Isuzu, the piston in the caliper has to move out in compensation for this loss of material. The requires that hydraulic fluid to be drawn from the brake master cylinder to replace the distance the disc brake pads had before they were worn on your Isuzu. This is the reason an owner can know if they are in need of replacing the pads without actually inspecting the braking component. When the fluid level in the brake master cylinder drops to a low level, the pads are worn sufficiently to warrant replacement.
The replacement of the disc brake pads is a simple process that only requires the removal of the wheel and the caliper. Since the Isuzu brake caliper is still attached to the braking system, it does not need to be bled of air. When the piston is pushed back into the caliper, the fluid level will rise in the master cylinder so there is no need for additional fluid to be added.