rected to the ERQ valve for each axle. Each ERQ
(In the following pages the emergency, relay,
valve directs air pressure to its power cluster. Each
quick release valve will be referred to as the ERQ
power cluster sends hydraulic pressure to its disc
valve.)
brake units which apply the brakes.
When the brake foot pedal is pushed, air is di-
OPERATION OF THE POWER CLUSTER
3. Piston loose on rod
THE POWER CLUSTER
Problem 2: Internal hydraulic pressure leak.
The power cluster is an air over hydraulic master
cylinder designed to multiply the force applied to
P r o b a b l e causes:
actuate the brakes, 15:l.
Air pressure enters at the port on the left, pushes
1. Worn cup seal
the air piston which in turn pushes the hydraulic
2. Corrosion in the cylinder
piston. The hydraulic section of the power cluster
operates just as any other standard brake master
P r o b l e m 3: External oil leak at the rear of the
cylinder.
cylinder.
POWER CLUSTER TROUBLESHOOTING
P r o b a b l e causes:
Problem 1: Air leaking from cylinder.
1. Worn cup seal
P r o b a b l e causes:
2. Corrosion in cylinder
1. Worn piston cup
Problem 4: Brake not releasing, "lock-up" (Make
sure hand valve is not applied.)
2. Dent or corrosion in cylinder shell
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