When working on a vehicle’s braking system, whether it be the installation of a new brake kit on your racecar or post-track maintenance, it is important that the manufacturer’s bleeding procedure is accurately followed to guarantee proper brake operation when you need it most.
When it comes to bleeding a dual master cylinder system, the bleeding procedure becomes more labor intensive and can become confusing, depending on the number of bleeder screws used on each caliper. Knowing this, Tilton Engineering made a video that guides the DIY minded through the process, using their 76-Series Master Cylinders and 600-Series pedal assembly.
Before you start, you’ll need to gather a few things:
- Two friends
- Properly sized wrench for master cylinder outlet fittings (if installing a new system or the reservoir went dry)
- Two properly sized wrenches for the caliper bleeder screws
- More than enough DOT-3 or DOT-4 brake fluid
- Clear brake fluid safe hose that fits snugly over the bleed nipple
- Two clear brake fluid safe bottles to catch the fluid
If you’re installing a new system, the master cylinders will need to be bled before you can prime the rest of the system. To begin, make sure that both reservoirs are adequately filled, and then loosen the outlet fittings on both cylinders.
At this point you can begin slowly pressing in the brake pedal and gently guiding it back up until fluid begins to drip from both fittings, then tighten the fittings again. Now you are ready to bleed the rest of the system without introducing any additional air from the reservoirs.
With a dual master cylinder system, pressing the brake pedal activates both the front and rear master cylinder, requiring that both calipers be bled simultaneously on each side (this is where you’ll need those friends). Before moving on, check the fluid level in the reservoirs and top it off when needed. Do your legs a favor, if the fluid level drops too low during the bleeding process, air will be reintroduce into the system and you will have to start the whole procedure over again, starting from the master cylinders.
The general bleeding process involves depressing the brake pedal with normal force, holding it at its lowest position while the caliper bleeder screw is slightly opened. Continue holding down the pedal until the bleeder screw is closed, then slowly release the pedal. Repeat this process until air bubbles are no longer visible, frequently topping off the fluid reservoirs.
For dual master cylinder systems using brake calipers with a single bleeder screw per unit, start on the passenger side — bleeding both the front and rear calipers simultaneously. Once air bubbles are no longer visible, both friends can move on to the driver side.
If your dual master cylinder system has two bleeder screws per caliper, you will also start with the passenger side of the vehicle. Servicing both front and rear calipers at the same time, open the inside bleeder screw first, repeating the process until air is no longer visible before continuing on to the outside bleeder. Once the passenger side has been bled, you can move on to the driver side, following the same procedure — start with the inside bleeder screw first, following with the outside screw.