Meritor PD 1591 Dry Disc Brake Calipers Maintenance Manual 4AA
This maintenance manual (MM 4AA) provides instructions for the service, repair, and installation of Meritor PD-1591 dry disc brake calipers used on AxleTech International axles. These brakes feature a floating caliper design with single or dual hydraulic cylinders.
Core Technical Specifications
Effective braking performance and component longevity depend on maintaining specific tolerances:
- Lining Wear Limits: Replace brake linings when the material is worn to a thickness of 1/8-inch (3.0 mm).
- Disc Wear Limits: The brake disc must be replaced if the thickness is reduced below the minimum specified by the manufacturer or if deep scoring exceeds .010-inch (0.25 mm).
- Disc Runout: The maximum allowable lateral runout for the brake disc is .008-inch (0.20 mm).
- Lining-to-Disc Clearance: During assembly, ensure a total clearance of .010-.030 inches (0.25-0.76 mm) between the linings and the disc.
Key Maintenance Procedures
- Cleaning: Use only solvent cleaners (isopropyl alcohol, kerosene, or diesel fuel) for ground and polished metal parts. Never use gasoline, water, or steam on these surfaces.
- Cylinder Service: When disassembling hydraulic cylinders, use low-pressure compressed air (max 20-30 psi) to remove pistons, keeping fingers away to avoid injury.
- Lubrication: Apply a thin film of approved silicone grease to the piston and cylinder bore during assembly to ensure smooth operation and prevent seal damage.
- Bleeding: The hydraulic system must be bled whenever a connection is loosened to ensure no air remains, which could result in spongy brakes or increased stopping distances.
Safety and Operational Warnings
- Dust Hazard: Do not use high-pressure air hoses or dry brushing to clean brakes, as airborne dust may contain hazardous fibers.
- Hydraulic Fluid: Use only the fluid specified by the vehicle manufacturer. Using incorrect fluid will damage piston seals and potentially cause brake failure.