Master Cylinders

1966 Early Broncos originally came with a single reservoir master cylinder, a design considered unsafe by modern standards. In 1967, Ford upgraded to a dual-circuit master cylinder that provides separate hydraulic circuits for the front and rear brakes, ensuring at least partial braking if one circuit fails. Tom's Offroad carries dual-circuit master cylinder upgrade kits designed to fit the early Bronco's firewall mounting location.

Yes, converting from drums to disc brakes requires a master cylinder without residual check valves, and sometimes a larger bore diameter designed for disc brake hydraulic pressure. The factory drum brake master cylinder will produce a spongy, low-pressure pedal with 4 wheel disc calipers. Tom's Offroad's disc brake conversion kits include the correct master cylinder, ensuring safe and firm pedal feel from the moment of installation.

Signs of a failing early Bronco master cylinder include a spongy or low brake pedal, a pedal that slowly sinks to the floor under steady pressure, brake fluid leaks at the firewall behind the master cylinder, and contaminated fluid in the reservoir. Any of these symptoms require immediate attention, do not drive the truck until the master cylinder has been inspected and replaced if necessary.

Replacing an early Bronco master cylinder involves removing the brake fluid reservoir cap and siphoning out the old fluid, disconnecting the brake lines at the master cylinder body, unbolting the unit from the firewall or booster, and installing the new unit in reverse order. Bench-bleed the new master cylinder before installation to remove trapped air, then bleed all four wheel cylinders or calipers after installation.

Adding a power brake booster to an early Bronco significantly reduces pedal effort and is especially recommended for trucks with disc brakes or those driven frequently in traffic. Booster and master cylinder combo kits designed for the early Bronco are available and mount to the factory firewall location. Pairing a booster upgrade with a disc brake conversion gives the truck a modern, confidence-inspiring brake feel. For even better braking, consider a Hydroboost brake unit for the ultimate stopping power.