Brake Master Cylinders & Reservoirs

A typical master cylinder has pistons with seals and springs within a bore inside a cast iron or aluminum housing. The fluid reservoir may be integral with the master cylinder body on cast iron master cylinders, but is more commonly an external nylon or plastic component attached to the top of the body and sealed with O-rings. Integral reservoirs have a single cap held on by a wire bail, while external reservoirs have one or two threaded caps.

The master cylinder can be mounted on the firewall, but is more commonly found on the front of the vacuum power booster. When you press on the brake pedal, a pushrod from the pedal or booster forces the pistons forward, pressurizing the fluid. When the pedal is released, a return spring forces the pistons back. Piston cup deflection and ports in the master cylinder bore ensure there is always a plentiful supply of fluid. All vehicles since 1967 have dual circuit master cylinders with two pistons, so that if there is a hydraulic failure in one circuit, the remaining circuit can provide enough pressure to stop the vehicle.

Master cylinders can leak fluid past the end seal or fail internally. Fluid leaks and air elsewhere in the system should be eliminated before condemning the master cylinder. Look for wetness under the master cylinder on the firewall or brake booster. It may be necessary to unbolt the master cylinder from the booster to find the leak. Moisture in the fluid can cause the master cylinder bore to corrode, and seals can deteriorate due to age and use. Either can result in the master cylinder developing an internal leak and complaints of a low pedal and poor stopping. External reservoirs and caps can develop cracks.

Regardless of the master cylinder problem, we can supply you with a replacement part that is manufactured to OE specifications, for precise fit and perfect performance, at an affordable price. We offer master cylinders, master cylinders with external reservoirs, and even master cylinder/vacuum brake booster combos for some applications. We also offer reservoirs and caps individually, as well as master cylinder rebuild kits for some applications. Some vehicles have fluid level sensors attached to the master cylinder. We have these sensors, plus we have bleeder tools that make short work of master cylinder bench bleeding.

If you want to upgrade your brakes and wow ‘em when you pop the hood down at the drive-in, we’ve got master cylinders for every kind of brake configuration - drums, disc/drums, and discs all around – in chrome and powder coated in your choice of colors. Or lose the OE shape entirely, and take your brakes and engine bay to the next level with a smooth, aluminum master cylinder with a chromed or polished finish. This a great look for a street rod or any custom and features a smooth, one-piece, master cylinder cap retained with flush mount threaded fasteners instead of the OE cap and wire bail. We also offer universal master cylinder/brake booster combos in chrome with single and dual diaphragms.