Dorman M66705 Brake Master Cylinder

Brake Master Cylinder for Moraine Brake Applications

The Dorman M66705 brake master cylinder is built for specific classic GM vehicles that use Moraine brakes and a 1-inch bore. It is made from new, high-quality materials and follows the original design and function for a direct replacement on listed Buick, Cadillac, Oldsmobile, and Pontiac applications.

• Brake master cylinder for Moraine brake systems
• 1-inch bore diameter for listed power brake applications
• Cast iron master cylinder body
• Reservoir included
• Two outlet ports
• Rearward outlet size: 9/16-18
• Sensor not included
• Mounting hardware not included

Detailed Product Overview

Dorman M66705 is a brake master cylinder engineered to match the original fit, function, and performance of the factory unit on select 1967-1970 GM vehicles. It is designed for vehicles with Moraine brakes and a 1-inch bore, including applications such as 1967-1970 Pontiac Bonneville and Catalina, 1967-1968 Pontiac Grand Prix, 1967-1970 Buick LeSabre and Riviera, and 1967-1968 Cadillac DeVille, Fleetwood, and Eldorado. This part cross-references Raybestos Brakes MC36234 for the same application.

Compatible With: 1967-1970 Buick LeSabre, 1967-1970 Buick Riviera, 1967-1970 Pontiac Bonneville, 1967-1970 Pontiac Catalina, 1967-1968 Pontiac Grand Prix, 1967-1968 Cadillac DeVille, 1967-1968 Cadillac Fleetwood, 1967-1968 Cadillac Eldorado, 1968-1969 Oldsmobile 98, 1968-1969 Oldsmobile Delta 88, and 1969 Oldsmobile Delta 88 and 98 applications listed with Moraine brakes and 1-inch bore requirements.

What This Part Helps Address

• Brake fluid leakage from a worn master cylinder
• Low or inconsistent brake pedal response
• Internal seal wear that affects hydraulic pressure
• Corrosion or damage in the original cast iron housing
• Restoration needs for classic GM brake systems

Installation Notes and Tips

Verify bore size, outlet configuration, and brake system type before installation. This unit includes the reservoir and uses two outlets; mounting hardware and a sensor are not included. Bleed the brake system thoroughly after installation and confirm all line connections match the rearward 9/16-18 outlet and secondary 0.5 thread specification.

Quality Assurance

Dorman designs this master cylinder as a precision replacement for the original part on the listed vehicles, using new materials for durability and safe operation. The M66705 is built to meet the fit and function requirements of the specified Moraine brake applications.