Product Description
The Bendix 12339 Hydraulic Brake Master Cylinder is a heavy-duty master cylinder designed for commercial vehicles equipped with hydraulic braking and Bendix Hydro-Max power brake systems.
The 12339 features a 2.00-inch (50.80 mm) bore and converts brake pedal and booster force into hydraulic pressure for the vehicle’s service brake circuits. The large-bore design is suited to medium-duty trucks and commercial chassis requiring high-volume hydraulic brake operation. A period commercial brake catalog specifically identifies the 12339 as the master cylinder used in certain Bendix Hydro-Max-equipped Navistar configurations.
Cross-referenced replacements use a reservoir-equipped dual-outlet design with 1/2"-20 and 9/16"-18 hydraulic outlet connections. Dorman and Raybestos both confirm a 2-inch bore for the corresponding M630277/MC390590 configuration.
Part Number: 12339
Brand: Bendix
Product Type: Hydraulic Brake Master Cylinder
Brake System: Hydro-Max / Hydraulic
Bore Size: 2.00 in. / 50.80 mm
Outlet Threads: 1/2"-20 and 9/16"-18
Reservoir: Included on common replacement configurations
Common Cross References: MC390590, M630277, 130.79031, F140488, M12339, 1681210C92, BRMC206
Because several commercial master cylinders have similar housings, verify the original part number, 2-inch bore, outlet threads, reservoir configuration, and mounting pattern before ordering.