ACDelco 18M72B Professional Brake Master Cylinder Assembly

The ACDelco 18M72B Professional Brake Master Cylinder is a premium replacement hydraulic component engineered to restore reliable braking performance. Built with a combination of cast iron and aluminum construction, this master cylinder is designed to deliver a precise fit without placing extra stress on the brake booster mounting.

Rubber internal components utilize both Ethylene Propylene (EPDM) and Styrene Butadiene (SBR) compounds, providing outstanding resistance to heat, corrosion, and fluid leakage. Strict geometrical tolerances ensure the body and plastic reservoir align perfectly for a leak-free seal.

Key Features:

• Cast iron and aluminum construction for strength and durability
• EPDM and SBR rubber seals for superior resistance to heat, corrosion, and leakage
• 1-1/8 in. (28.575 mm) bore diameter for proper hydraulic pressure
• Meets SAE J1153 and J1154 brake performance testing requirements
• Pressure tested prior to shipment for safe, confident braking
• Piston assembly and return spring engineered to prevent brake drag and premature pad wear
• Geometrical tolerances ensure proper body-to-reservoir fit
• Ready to bench bleed — no assembly required
• 2-port outlet configuration with 2-bolt mounting
• Includes reservoir cap and bleeder hoses

The ACDelco 18M72B ships ready to install straight out of the box with no additional assembly needed, making it an efficient choice for professional technicians and DIY mechanics alike. As an ACDelco Professional series part, it is manufactured to meet expectations for fit, form, and function.