Dorman M39578 Brake Master Cylinder

Reliable Brake Master Cylinder for Chevrolet and GMC Vehicles

The Dorman M39578 Brake Master Cylinder is engineered to restore proper brake hydraulics in select Chevrolet and GMC models. Designed with precision, this master cylinder ensures consistent brake fluid pressure for safe and effective braking performance.

• Compatible with Chevrolet Astro, GMC G10, G20, P20, P2500, and Safari models
• Dual bore diameters: 1.125 inch and 1.578 inch for balanced braking
• Constructed from durable aluminum for corrosion resistance and longevity
• Includes reservoir for brake fluid storage
• Two outlets with rearward outlet size 1/2-20 and secondary outlet thread diameter 9/16-18
• Package contains master cylinder only; mounting hardware not included

Detailed Product Features and Specifications

The Dorman M39578 master cylinder features dual bore diameters of 1.125 and 1.578 inches, designed to provide optimal hydraulic pressure distribution between front and rear brakes. Its aluminum construction offers enhanced durability and resistance to corrosion, which is critical for maintaining brake system integrity over time. The included reservoir simplifies installation by providing a ready-to-use brake fluid container. This master cylinder has two outlets, with a rearward outlet size of 1/2-20 and a secondary outlet thread diameter of 9/16-18, ensuring compatibility with the brake lines on Chevrolet Astro and GMC G-series vans and trucks.

Applications and Common Brake System Issues Addressed

• Restores brake fluid pressure in vehicles experiencing spongy or unresponsive brakes
• Replaces worn or leaking master cylinders causing brake fluid loss
• Solves uneven braking due to faulty bore diameters or internal seals
• Addresses brake pedal sinking or failure to maintain pressure
• Improves overall brake system reliability in Chevrolet Astro and GMC G10, G20, P20, P2500, and Safari models

Installation Notes and Tips

Installation of the Dorman M39578 master cylinder requires proper brake system bleeding to remove air and ensure optimal hydraulic function. Note that mounting hardware is not included, so existing hardware should be inspected and replaced if necessary. Verify compatibility with your specific vehicle model and year before installation. It is recommended to consult a professional mechanic if unfamiliar with brake hydraulic systems.

Quality Assurance and Warranty Information

Dorman manufactures this brake master cylinder to meet or exceed OEM specifications, using high-quality aluminum materials for durability. While mounting hardware is not included, the product is designed for direct replacement in compatible Chevrolet and GMC vehicles. Warranty coverage details should be confirmed at the point of purchase or through Dorman's official channels.