Dorman M630070 Brake Master Cylinder

Dorman M630070 Brake Master Cylinder

The Dorman M630070 brake master cylinder is a direct replacement for select BMW applications that require a 21 mm bore. Built from new aluminum materials, it is engineered to match the original master cylinder’s design, function, and performance for dependable brake hydraulic operation.

Use this brake master cylinder for BMW 525i, 530i, 540i, M5, 740i, 740iL, 750iL, and X5 applications listed below. The M630070 is a practical OE-style replacement when the original unit is worn, leaking, or no longer maintaining proper pedal feel.

Key Features

• 21 mm master cylinder bore diameter
• Aluminum master cylinder construction
• Three outlet ports
• New, high-quality replacement materials
• Package includes master cylinder only
• No reservoir included
• No sensor included
• Mounting hardware not included

Detailed Product Information

This brake master cylinder is built to match the original hydraulic layout on specific BMW models, including 2003 BMW 525i, 2001-2003 BMW 530i, 2003 BMW 540i, 2003 BMW M5, 2001-2002 BMW 540i, 2000-2002 BMW M5, 1999-2001 BMW 740i, 1999-2001 BMW 740iL, 1999-2001 BMW 750iL, 2001 BMW X5, and 2000 BMW X5. It features rearward outlet sizes of M10 x 1.0 and M10 x 1.0, plus a secondary outlet thread diameter of M12 x 1.0 with 1.0 thread pitch. This part cross-references Raybestos Brakes MC390633 for the same application.

For shoppers searching for a BMW brake master cylinder 21 mm bore, BMW 540i master cylinder replacement, or BMW X5 brake master cylinder M630070, this part provides the correct hydraulic configuration for the listed vehicles. It is also a fitment-based replacement for BMW 740i and BMW M5 brake system service where the 21 mm bore specification is required.

What It Helps Address

• Soft or inconsistent brake pedal feel
• Brake fluid leakage from a worn master cylinder
• Loss of hydraulic pressure in the brake system
• Internal seal wear affecting braking response
• Replacement needs after master cylinder failure

Installation Notes and Tips

Confirm the vehicle’s bore size, outlet thread sizes, and fitment notes before installation. This unit does not include a reservoir, sensor, or mounting hardware, so reuse or source those components as needed. Proper brake bleeding is required after installation to remove air from the hydraulic system and restore pedal firmness.

Quality Assurance

Dorman manufactures this master cylinder as a new replacement part using high-quality materials and OE-style engineering for the listed BMW applications. The M630070 is built to match original design and performance requirements for brake hydraulic service.