Braking Systems
Hydraulics and components
The brake system applies Pascal's principle: pressure applied to a confined fluid is transmitted equally, so a larger caliper piston produces greater clamping force. The master cylinder, proportioning or electronic brake distribution, lines, hoses, calipers and wheel cylinders form the circuit. A spongy pedal indicates air in the system or a leaking component; a pedal that sinks under steady pressure suggests an internal master cylinder bypass.
Friction and ABS
Disc brakes use a caliper and pads; drums use shoes expanding against a rotating drum. Understand fade from heat, glazing, and the need to measure rotor thickness and runout rather than judging by eye. Anti-lock braking monitors wheel speed sensors and modulates pressure through the hydraulic control unit; a wheel speed fault disables ABS and often traction control. Parking brakes may be mechanical cable or electric motor actuated.
Fluid and service
Glycol-based fluids DOT 3, DOT 4 and DOT 5.1 are hygroscopic and absorb moisture, lowering the boiling point; DOT 5 is silicone based and must never be mixed with glycol fluid. Bleeding follows the manufacturer's sequence, usually furthest from the master cylinder first, and ABS units may need a scan-tool bleed routine.
Rule of thumb: test brake fluid moisture and replace on the OEM interval, commonly around two years, and always flush with the specified fluid. Traps include assuming a hard pedal means good brakes, ignoring hose swelling as a cause of drag, and skipping the scan-tool routine after ABS hydraulic work.