Dorman M390591 Brake Master Cylinder

Brake Master Cylinder for Honda Civic

This Dorman brake master cylinder is built for 1999-2000 Honda Civic models with drum brake wheel cylinders that require a 7/8 in. bore size. Part number M390591 is engineered to match the original master cylinder’s design, function, and performance using new, high-quality materials.

• Direct replacement brake master cylinder for specific Honda Civic applications
• 0.875 in. bore diameter for the listed fitment
• Aluminum master cylinder construction
• Reservoir included for a complete hydraulic assembly
• Sensor included
• Two outlet design with M10 x 1.0 rearward outlet thread

OE-Style Hydraulic Replacement

Dorman M390591 is a brake master cylinder designed to restore hydraulic pressure at the brake pedal and support consistent brake system operation. It is a fitment-specific replacement for 1999-2000 Honda Civic, and the 7/8 in. bore size matches the application noted for drum brake wheel cylinders. This part cross-references Raybestos Brakes MC390591 for the same application.

Common Issues This Part Addresses

• Low or inconsistent brake pedal pressure
• Internal master cylinder leakage
• Brake fluid loss at the hydraulic unit
• Uneven brake response from a worn master cylinder
• Brake warning sensor-related replacement needs

Installation Notes

Mounting hardware is not included. Before installation, verify the bore size, outlet thread size, and reservoir/sensor configuration against the original unit. Bench bleed the master cylinder before connecting brake lines, then bleed the full brake system after installation. Confirm the vehicle is a 1999-2000 Honda Civic with the listed drum brake wheel cylinder application before ordering M390591.

Quality Assurance

Dorman manufactures this master cylinder as a new replacement part using high-quality materials and application-specific engineering to match the original unit’s design and performance for the listed Honda Civic fitment.