Dorman M390258 Brake Master Cylinder

Reliable Brake Master Cylinder for Dodge Ram 2500 and 3500

The Dorman M390258 Brake Master Cylinder is engineered to restore proper brake function in Dodge Ram 2500 and Ram 3500 trucks. Designed with durable aluminum construction and a built-in reservoir, this master cylinder ensures consistent hydraulic pressure for safe braking performance.

Key Features of the Dorman M390258 Brake Master Cylinder

• Master cylinder bore diameter of 1.25 inches for precise hydraulic control
• Constructed from lightweight, corrosion-resistant aluminum material
• Includes an integrated reservoir for brake fluid storage
• Equipped with two outlets to support dual-circuit brake systems
• Rearward outlet size: 1/2-20 thread for secure brake line connection
• Secondary outlet thread diameter: 9/16-18 for compatibility with factory brake lines
• Package contains the master cylinder unit only; mounting hardware not included

Detailed Description and Specifications

This Dorman brake master cylinder (part number M390258) is specifically designed for use in Dodge Ram 2500 and Ram 3500 models, providing a direct replacement for the original equipment. The 1.25-inch bore diameter allows for accurate brake fluid displacement, which is critical for maintaining proper brake pedal feel and stopping power. The aluminum construction offers resistance to corrosion and heat, extending the service life of the component. The included reservoir simplifies installation and maintenance by housing the brake fluid in a sealed, integrated unit. With two outlets featuring standard thread sizes (1/2-20 rearward and 9/16-18 secondary), this master cylinder supports dual-circuit brake systems commonly found in heavy-duty trucks.

Common Applications and Problem Resolution

• Restores brake pressure in Dodge Ram 2500 and 3500 trucks experiencing soft or spongy brake pedal feel
• Replaces leaking or damaged master cylinders causing brake fluid loss
• Addresses brake system failure due to worn internal seals or corrosion
• Improves brake responsiveness in trucks with inconsistent stopping performance
• Serves as a direct replacement for OEM master cylinders in compatible Dodge Ram models

Installation Notes and Tips

• Ensure brake fluid reservoir is properly filled and free of contaminants before installation
• Bleed the brake system thoroughly after installation to remove air and restore hydraulic pressure
• Verify thread sizes (1/2-20 rearward and 9/16-18 secondary) match existing brake lines for proper fitment
• Use appropriate tools to avoid damaging aluminum surfaces during installation
• Mounting hardware is not included; reuse original hardware or source compatible fasteners

Quality Assurance and Warranty Information

Dorman manufactures the M390258 brake master cylinder to meet or exceed OEM specifications for fit, form, and function. The aluminum construction and integrated reservoir are designed for durability under demanding conditions typical of Dodge Ram 2500 and 3500 trucks. While mounting hardware is not included, the product undergoes quality checks to ensure reliable performance. Warranty coverage details should be confirmed through the original product documentation or Dorman's official resources.