Atwood Mobile Products MPD 85233 User Manual

LITERATURE NUMBER MPD 85233

DISC BRAKE ACTUATORS

9

ENGLISH, FRANÇAIS (et Canada)

USED FOR DISC BRAKE APPLICATIONS

•Installation •Operation •Maintenance

REFER TO MPD 85778 FOR COMPLETE HYDRAULIC SURGE BRAKE INSTALLTION, OPERATION AND MAINTENEANCE INSTRUCTIONS.

SAFETY ALERT SYMBOLS

Safety Symbols alerting you to potential personal safety hazards. Obey all safety
messages following these symbols.

 WARNING  CAUTION

avoid possible avoid possible
injury or death injury and/or property damage

FOR YOUR SAFETY READ ALL INSTRUCTIONS

BEFORE INSTALLATION AND OPERATION

Installer: Provide these instructions to the consumer.

INSTALLATION - BRASS ORIFICE FITTING

 CAUTION

DAMAGE TO BRAKE ACTUATOR OR VEHICLE

• If brass orifice fitting is not installed, trailer-braking action may cause
vehicle(s) to shake during brake applications.

The brass orifice fitting installed in the master cylinder of the brake actuator
assembly must remain in the hydraulic circuit to the brakes of the trailer.

If the brass orifice fitting must be moved to accommodate plumbing for
a back up solenoid valve, it must be replaced in the hydraulic circuit in
line to brakes.

Consumer: Keep documents for future reference.

SCHEMATIC REPRESENTATION OF HYDRAULIC CIRCUIT

INSTALLATION - DISC BRAKE ACTUATOR SOLENOID BACK-UP VALVE

 WARNING

DEATH OR PERSONAL INJURY

• This system requires the solenoid wire leads be connected ONLY into the tow

vehicle back-up light circuit.

8,000 LB. ACTUATORS are equipped with a solenoid back-up valve.

1. Connect the solenoid valve wire leads to the tow vehicle back-up
light circuit.

2. Connect trailer brake line to actuator.

3. Bleed brake system.

6,000 LB. ACTUATORS are not equipped with a solenoid back-up

valve. Contact Atwood (815-877-5700) for a Solenoid Back-up Valve
Kit - MPD 80376.

To install Atwood solenoid back-up valve -

1. Remove the plug in return port of master cylinder (this is the
upper port in the master cylinder).

2. Install straight barbed fitting (torque to 16-20 in/lb).

3. Install assembly in supply port of master cylinder (this is the lower
port in the master cylinder).

4. Connect the solenoid wire leads only into the reverse back-up
light circuit.

5. Connect trailer brake line to actuator.

6. Bleed brake system.

 CAUTION

BRAKE FAILURE

•

use brake fluid drained from brake system in refilling master cylinder.

DO NOT

Brake fluid can be contaminated from the system.

• Contaminated brake fluid in system could plug brass orifice fitting. This
could render brakes inoperative.

Be especially careful to clean all fittings, tubing and threads between
master cylinder and brass orifice fitting. A very small particle of dirt or
thread sealant can plug the hole in the orifice.

• Do not use Teflon

• If a liquid or paste thread sealant is used, keep it back two threads from end
of male fitting.

• Do not apply sealant to female threads. Clean female threads thoroughly.

BLEED BRAKE SYSTEM

1. Remove master cylinder filler cap and fill reservoir with DOT type 3
or 4 automotive brake fluid.

2. Check all hydraulic line fittings & connections to make sure they are
leak free.

3. At brake assembly, connect a bleeder hose to bleeder fitting on wheel
cylinder and submerge free end in a container with brake fluid.
reuse brake fluid.

NOTE: Use power bleeder or bar with 2˝ diameter hitch ball attached.

Do not use breakaway cable for purpose of bleeding brake system. If
a power bleeder is used air pressure 35 PSI is most effective.

NOTE: On tandem axle trailers, bleed brakes on rear most axle furthest

from the actuator first.

4. Loosen bleeder fitting at top of brake assembly.

5. Apply actuator and tighten bleeder fitting. Return actuator to
forward position. Again, loosen bleeder valve and apply actuator.
Repeat this procedure until fluid expelled from bleeder hose is free
of air bubbles. It is helpful to lower the trailer tongue to promote air
bubble movement in the brake tubing. It is also helpful to tap gently
along the brake tubing during brake bleeding to keep air bubbles
from sticking to the inside of the brake tubing. During this
procedure, master cylinder reservoir fluid level must be maintained
at no less than 1/2 full and no more than 1/2˝ from top of reservoir.

6. When no air bubbles are visible, close bleeder valve securely and
remove bleeder hose.

7. Repeat

8. If installation is tandem axle with brakes on both axle, repeat

9. After bleeding has been completed, re-check fluid level in master

STEP 1-6 for remaining brake, then brakes on forward axle.

bleeding procedure on rear axle brakes for second time to assure
positive purging of all air in system.

cylinder.

 WARNING

DEATH OR PERSONAL INJURY

™

tape on fittings.

Effective 12/04/07

DO NOT