BLEEDING

Vehicle Brake System: Always use clean fluid conforming to vehicle manufacturer’s recommendations.

691 Power Unit: Check the CAUTION label on the

691 Power Unit reservoir for proper fluid type. Refer to Figure 13.

All electrical connections must be completed and the power unit reservoir filled with proper fluid before bleeding. The hydraulic brake system must be bled whenever any line has been disconnected. Although we recommend the use of pressure bleeding equipment when bleeding the system, some vehicle manufacturers do not advise certain bleeding methods. Refer to Vehicle Manufacturers bleeding recommendations. When pressure bleeding, use a system pressure of 1.72-2.07 bar (25-30 psi).

Tips on Bleeding Brake Systems

1.Patience is often necessary. Brake fluids can be easily aerated by being forced through tubes too fast or agitating them. Once brake fluid has been aerated, the best way to get the air back out is to let it sit. Several hours or overnight may be necessary.

2.While bleeding, make every effort to move the fluid slowly. This is especially important when applying the brake pedal and when opening bleeder screws.

3.Avoid rapid pumping of the brake pedal as it can cause the fluid to become aerated.

4.Always wear safety glasses and be cautious when opening bleeder screws with any pressure applied. Air pockets will shoot the fluid out at a rapid rate.

5.Connect a length of poly-style air line from the bleeder screw into a container to recapture the fluid during the bleeding process.

6.In some cases, gravity bleeding is the best form of bleeding.

7.Start bleeding process at the actuators and work toward the foundation brakes.

8.Even when the brake system seems to be well bled, it may still contain small amounts of air. We recommend re-bleeding the brake system after the vehicle has been parked overnight.

Bleeding Procedures

NOTE

To assure successful brake system bleeding, complete all bleeding procedure steps in the order that they are listed.

Brake System

Brake System

Bleed Point

Bleed Point

FIGURE 22

1.Disconnect the vehicle horn and other warning devices.

2.Be sure the 691 Power Unit reservoir remains filled with the proper fluid during entire bleeding process. Check the CAUTION label on the 691 Power Unit reservoir for proper fluid type.

3.Make sure the vehicle master cylinder reservoir is full of fluid specified by the vehicle manufacturer.

4.Gravity Bleed - After the initial installation, DO NOT apply the brake pedal. Remove the cap from the master cylinder reservoir. One at a time, open each bleeder screw in the vehicle brake system beginning with bleeder screws on the actuators and moving outward to the foundation brakes. NOTE: In some situations, to save time, all bleeder screws may be opened simultaneously. Do not deplete reservoir fluid level. When a steady stream of fluid is present, close the bleeder and proceed to the next. If gravity flow is not obtained within 5 minutes, proceed to next step. (Also check for blocked or crimped lines, or loops in tubing where air may be trapped).

5.Manual Bleed - Manually bleed the brakes, depress- ing and releasing brake pedal slowly and to disperse fluid through the brake system without agitating it. Do not depress pedal when bleeder screw is closed. Do not release pedal when bleeder screw is open. Bleed 691 Actuators first. After actuators are bled, continue by bleeding foundation brakes.

A.Open bleeder screw, then slowly apply the pedal to the limit of its stroke.

B.Close the bleeder and slowly release the pedal.

C.Repeat this process multiple times at each bleed point without pumping the pedal in-between.

10