6.2 Brake Pedal, Hydraulics, Friction Components & Parking Mechanism

Physical condition comes before the performance number

A vehicle can produce an acceptable stop while containing a component likely to fail. Page 8-1 therefore combines mandatory equipment, condition, performance, and modification reasons.

Pedal, assistance, and hydraulic supply

Reject a service-brake pedal that is insecure, spongy, creeps under pressure, has a dangerously deteriorated non-slip surface, or has excessive travel indicated by travel reducing after one or two applications. The page does not prescribe a universal “one-third reserve travel” measurement.

Inspect vacuum hoses/pipes, servo, pump, and drive belt for security, leakage, damage, and adequate operation. Inspect the master cylinder for fluid leakage, insecurity, excessive corrosion, and a reservoir level below the visible minimum. Valves must operate and be secure, leak-free, and not excessively corroded.

A valid booster functional check can help establish adequate operation, but do not present one workshop sequence as the only VIRM method where the manual states the required outcome.

Pipes and flexible hoses

A rigid brake pipe fails for leakage, insecurity, deformation, chafing, or corrosion damage such as pitting or a noticeable change in outside diameter. There is no safe “20% flattened” allowance in the page.

A flexible hose fails for leakage, insecurity, bulging under pressure, twisting, stretching, chafing, exposed reinforcing cords from cracked sheathing, excessively corroded fittings, or an end fitting not attached by swaging, machine crimping, or a similar process. Inspect through steering and suspension movement where necessary and safe.

Foundation components

Inspect callipers, backing plates, wheel cylinders, discs/drums, and friction material where visible without removing components. Reject visible leakage, insecurity, severe corrosion, seizure, fracture/damage, contamination, or wear beyond manufacturer specifications. Friction material fails when below manufacturer specification, separating from its backing or shoe, or contaminated.

The current page does not establish a universal 1.5 mm brake-pad or shoe limit or a universal groove-depth allowance. Use a visible manufacturer discard specification where available; do not dismantle solely to obtain a measurement outside the WoF procedure.

Also reject a service-brake component showing signs of heating or welding after original manufacture.

Parking-brake hardware

Check lever travel and security, accidental-release risk, and damage/corrosion/fracture within 150 mm of the lever mounting. Inspect cables for knots, fraying, excessive corrosion, deterioration, and auxiliary tensioners. Rods and guides must not be excessively corroded or worn. Parking components showing post-manufacture heating or welding are rejected.

Inspection method

1. Observe warning lamps and fluid level before disturbing the controls.
2. Apply the pedal and assess security, feel, travel, and holding behaviour.
3. Confirm assistance and inspect vacuum equipment.
4. Trace every visible hydraulic pipe and hose, including at clips and flex points.
5. Inspect visible callipers/cylinders, discs/drums, linings, plates, and contamination.
6. Operate and inspect the parking mechanism and its mountings.
7. Complete performance testing only by a safe approved method.

Scenario

Visible brake pads appear thin, but no manufacturer minimum can be established and the material remains attached and uncontaminated. The inspector must not invent a 1.5 mm statutory threshold. If the pad is visibly below a known manufacturer limit, separating, or contaminated, the specific reason applies.

Evidence and interaction

Brake-fluid level below the visible minimum is a reason for rejection; topping it up during inspection would hide evidence and does not locate worn friction material or leakage. A dark colour alone is a service concern unless another VIRM condition is present. Similarly, surface colour on a pipe is not automatically excessive corrosion—look for pitting, loss of section, deformation or a noticeable change in outside diameter.

Contamination links components: a leaking axle seal can wet a disc, drum or lining even though the hydraulic system is dry. Record both the source where established and the affected brake condition. After pedal operation, check that brakes release; a strong stop followed by binding is still a performance failure.

Mechanical and electronic boundaries

A brake inspection does not authorise component removal. Use viewing openings, accessible surfaces, measured performance and manufacturer information. If the disc’s stamped limit is hidden, do not dismantle it merely to search; record only a reason established by the WoF method. Likewise, an electronic pad-wear message is not the ABS/brake-system warning described by the advanced-system reason, though visible friction material can still fail against manufacturer specification.

Inspect repairs as critically as original parts. A replacement hose must route without stretch, twist or chafe through full steering/suspension movement; a new pipe must be secure and free of damaging deformation. A recent invoice proves work was charged, not that condition now complies.