Dorman M390249 Brake Master Cylinder

Reliable Brake Master Cylinder for Buick, Cadillac, and Chevrolet

The Dorman M390249 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 sizes (M11 x 1.5 rearward, M12 x 1.0 secondary)
• Master cylinder bore diameter of 40 mm & 1-1/8 inch for accurate hydraulic pressure
• Part number M390249 for exact replacement

Product Details and Specifications

This brake master cylinder is designed without mounting hardware, allowing for direct replacement using existing components. The aluminum construction provides strength and resistance to wear, while the included reservoir simplifies installation and maintenance. The unit features two outlets to accommodate brake line connections, with a rearward outlet size of M11 x 1.5 and a secondary outlet thread diameter of M12 x 1.0, both with a thread pitch of 1.0. The bore diameter measures 40 mm (1-1/8 inch), ensuring compatibility with the hydraulic system requirements of the Buick Caprice, Cadillac Fleetwood, and Chevrolet Roadmaster.

Compatible Vehicles and Applications

• Buick Caprice brake system restoration
• Cadillac Fleetwood hydraulic brake repairs
• Chevrolet Roadmaster brake master cylinder replacement
• Addresses issues such as brake fluid leaks, spongy brake pedal, and loss of hydraulic pressure
• Suitable for vehicles requiring a 40 mm bore diameter master cylinder with dual outlets

Installation Notes and Tips

Installation requires removal of the existing master cylinder and proper connection of brake lines to the specified outlet threads. Since mounting hardware is not included, retain original mounting bolts and brackets. Bleed the brake system thoroughly after installation to remove air and ensure optimal brake performance. Verify thread sizes (M11 x 1.5 rearward and M12 x 1.0 secondary) before connecting brake lines to avoid cross-threading.

Quality Assurance and Warranty

Dorman parts are manufactured to meet or exceed OEM standards for fit, form, and function. The M390249 Brake Master Cylinder undergoes rigorous quality control to ensure durability and reliable operation. While specific warranty details may vary, Dorman typically offers a limited warranty covering defects in material and workmanship.