Dorman M390259 Brake Master Cylinder

Reliable Brake Master Cylinder for Select GM and Dodge Models

The Dorman M390259 Brake Master Cylinder is engineered to restore proper brake hydraulics in your vehicle. Designed for compatibility with various Cadillac, Chevrolet, Dodge, and GMC trucks and SUVs, this master cylinder ensures consistent brake fluid pressure and reliable stopping power.

• Constructed from durable aluminum for corrosion resistance
• Includes reservoir for brake fluid storage
• Two outlet ports with precise thread sizes (1/2-20 rearward, 9/16-18 secondary)
• Master cylinder bore diameter of 40 mm & 1-1/8 inch for accurate fluid displacement
• Compatible with multiple models including Chevrolet Blazer, C1500, Escalade, Dodge Ram 1500, and GMC Yukon

Product Details and Specifications

The Dorman M390259 master cylinder features a robust aluminum body that resists wear and corrosion, extending the service life of your brake system. It comes complete with an integrated reservoir, eliminating the need for separate fluid storage components. The unit has two outlets designed to fit specific brake line connections, with a rearward outlet size of 1/2-20 and a secondary outlet thread diameter of 9/16-18. The bore diameter measures 40 mm & 1-1/8 inch, ensuring proper hydraulic pressure for effective braking performance. This part is compatible with a range of vehicles including Cadillac Escalade, Chevrolet Tahoe, GMC Yukon, and Dodge Ram 1500 models, making it a versatile replacement option.

Common Applications and Problem Resolution

• Restores brake fluid pressure in vehicles experiencing soft or spongy brake pedal feel
• Replaces master cylinders with internal leaks or worn seals
• Addresses brake fluid reservoir damage or contamination issues
• Solves inconsistent braking caused by faulty hydraulic components
• Improves brake system reliability in older Chevrolet, GMC, Cadillac, and Dodge trucks and SUVs

Installation Notes and Tips

Installation of the Dorman M390259 master cylinder requires basic brake system knowledge and tools. Since mounting hardware is not included, retain original fasteners or source compatible replacements. Bleed the brake system thoroughly after installation to remove air and ensure proper hydraulic function. Verify thread sizes on brake lines match the 1/2-20 rearward and 9/16-18 secondary outlets before installation. Always follow vehicle-specific service manual instructions for safety and accuracy.

Quality Assurance and Warranty Information

Dorman manufactures this brake master cylinder to meet or exceed OEM specifications, using quality aluminum materials and precise machining. While mounting hardware is not included, the product is designed for direct replacement fitment on compatible Cadillac, Chevrolet, Dodge, and GMC models. Please consult Dorman’s warranty policy for coverage details on the M390259 part number.