ACDelco 18M1159B Professional Brake Master Cylinder Assembly

The ACDelco 18M1159B Professional Brake Master Cylinder is a premium-grade hydraulic brake component engineered to restore safe, confident braking performance. Built with both aluminum and iron castings, this master cylinder delivers the precise fit and long-term durability required for a reliable brake system repair.

This unit features dual rubber compound internals — Ethylene Propylene (EPDM) and Styrene Butadiene (SBR) — selected specifically for superior resistance to heat, corrosion, and fluid leakage. The geometrical tolerances ensure the body and plastic reservoir align perfectly, while the included piston assembly and return spring help eliminate brake drag that can accelerate pad wear.

Key Features:

• Aluminum construction with a 34mm (1.34") bore diameter
• EPDM and SBR rubber components for heat and corrosion resistance
• Meets SAE J1153 and J1154 brake performance testing requirements
• Pressure tested for safe and confident braking
• Cast iron and aluminum specifications — no added stress on brake booster mounting
• Reservoir cap included; bleeder hoses included
• 2 mounting holes; 2 brake line ports
• Ready to bench bleed and install — no assembly required

Specifications:

• Bore Diameter: 34mm (approx. 1.34 in)
• Mounting Holes: 2 (0.413 in diameter)
• Port Quantity: 2
• Primary Outlet Thread Diameter: 0.5 in (12.7mm)
• Material: Aluminum
• Reservoir Cap Included: Yes
• Bleeder Hoses Included: Yes
• Brake Booster Included: No

Backed by ACDelco's 24-Month/Unlimited Mile Limited Warranty, this Professional series brake master cylinder is manufactured to meet the expectations for fit, form, and function as a high-quality replacement part.