Dorman M390127 Brake Master Cylinder

Reliable Brake Master Cylinder for Buick, Cadillac, and Chevrolet

The Dorman M390127 Brake Master Cylinder is engineered to restore proper brake hydraulics in select Buick, Cadillac, and Chevrolet models. Designed with an aluminum body and an included reservoir, this master cylinder ensures consistent brake fluid delivery for safe and effective braking performance.

• Constructed from durable aluminum for corrosion resistance
• Includes reservoir for brake fluid containment
• Compatible with Buick Caprice, Cadillac Fleetwood, and Chevrolet Roadmaster
• Features dual outlets with precise thread specifications (M11 x 1.5 rearward outlet, M12 x 1.0 secondary outlet)
• Master cylinder bore diameter of 40 mm & 1-1/8 inch for accurate hydraulic pressure

Product Details and Specifications

The Dorman M390127 master cylinder is designed to meet the exacting requirements of brake hydraulics systems in full-size luxury and performance vehicles such as the Buick Caprice, Cadillac Fleetwood, and Chevrolet Roadmaster. Its aluminum construction provides strength and resistance to corrosion, extending the service life of the component. The included reservoir simplifies installation by providing a ready-to-use brake fluid container. This master cylinder features two outlets, with a rearward outlet sized M11 x 1.5 and a secondary outlet thread diameter of M12 x 1.0, ensuring compatibility with the vehicle’s brake lines. The bore diameter of 40 mm (1-1/8 inch) is engineered to deliver consistent hydraulic pressure for reliable braking response.

Applications and Common Issues Addressed

• Restores brake fluid pressure in Buick Caprice brake systems
• Replaces worn or leaking master cylinders in Cadillac Fleetwood models
• Eliminates spongy or unresponsive brake pedal feel in Chevrolet Roadmaster vehicles
• Prevents brake fluid leaks that can lead to reduced braking efficiency
• Addresses master cylinder failure symptoms such as brake warning lights or pedal sinking

Installation Notes and Tips

When installing the Dorman M390127 master cylinder, ensure the brake system is properly bled to remove air and maintain hydraulic integrity. The included reservoir should be filled with the manufacturer-recommended brake fluid before installation. Verify thread sizes (M11 x 1.5 rearward outlet and M12 x 1.0 secondary outlet) match the vehicle’s brake line fittings to avoid leaks. Although mounting hardware is not included, the unit is designed to fit directly into the original mounting points on compatible Buick, Cadillac, and Chevrolet models.

Quality Assurance and Warranty

Dorman manufactures this brake master cylinder to meet or exceed OEM specifications for fit, form, and function. The aluminum construction and precise machining contribute to long-term durability. While specific warranty details are not provided here, Dorman products typically come with a limited warranty covering defects in materials and workmanship. Consult product documentation or the manufacturer for exact warranty terms.