General Service Diagnosis; Pedal Goes To Floor; Spongy Pedal; Bleeding - JLG GRADALL 522D Owner's/Operator's Manual

GENERAL SERVICE DIAGNOSIS

With Engine Off --

PEDAL GOES TO FLOOR

1.
Brake not adjusted
1.
Check adjustment
2. Air in system
2. Bleed brakes
3. Inoperative brakes
3. Check brakes
4. Blown hydraulic line
4. Check brake line
5.
Worn out primary cup
5. Check by making sure brakes
are properly adjusted, in good
operating condition, and
system well bled. If pedal
continues to go to the floor,
service brake valve.

SPONGY PEDAL

1. Air in system
1.
Bleed brakes
PEDAL IS FIRM BUT STOPS TOO
NEAR FLOOR
1. Brakes out of adjustment
1.
Adjust brakes

BLEEDING

The MICO Open Center Power Brake
Valve and remaining brake system
are sometimes difficult to bleed. The
difficulty arises when the hydraulic
oil used does not flow easily through
lines and small holes by means of
gravity. Generally, to effectively
remove air, oil must be forced into
the brake valve master cylinder
cavity and the rest of the system.
MANUAL BLEEDING
PROCEDURES
1.
Start engine and allow enough
time to pass for the system to
become filled and thoroughly
flushed with oil.
2.
With engine still running, one
person can stroke the brake pedal
while another person opens and
closes the brake bleeder screws.
3.
Only on the down stroke of the
brake pedal, open bleeder screw
(14)
2. Inoperative brakes
2. Check for wear
3. Displacement problem
3. Wheel cylinders too large for
valve to handle properly.
Consider alternate braking
valve.
PEDAL IS FIRM BUT BRAKING IS
INADEQUATE TO STOP VEHICLE
IN EVENT OF ENGINE FAILURE
1. Pedal ratio too small
1. Increase pedal ratio
2. Brakes inoperative
2. Check brakes for wear or oily
brakes
With Engine Running --
PEDAL GOES DOWN PART WAY
THEN BOUNCES BACK
1. Insufficient flow from pump
1. Check and fill reservoir
2. Small volume from pump at idle
2.
Crack throttle and recheck
Make sure
CAUTION:
machine is in a safe
and controlled state
before attempting
any servicing
including bleeding
the brake system.
Manual and pressure bleeding are
two methods of bleeding a brake
system. MICO recommends using
on the brake closest to brake
valve first. When all flow stops
from bleeder, close it and allow
pedal to return to rest.
4.
Wait at least 30 seconds and
repeat the process until all air has
been expelled from that brake.
Then go on to the next closest
brake bleeder and repeat process
until all brakes have been bled.
3. Brakes not adjusted
Check adjustment
3.
4. Air in system
4. Bleed system
NO POWER STEERING OR OTHER
DOWNSTREAM
ACTION AT ANY TIME
Hydraulic lines crossed
1.
Recheck circuit
1.
No hydraulic action at any time
2.
Check and fill reservoir. Check
2.
relief valve setting on pump.
Check for proper rotation at
pump, vee belt, sheared keys,
etc.
NO OR SLOW POWER STEERING
WITH BRAKES APPLIED
1. Recheck relief valve on pump for
proper setting
2. Check and fill reservoir
3. Check and tighten pump belt if
necessary
one of these two methods of
the
bleeding the Open Center Power
Brake Valve and the rest of the brake
system.
Be sure brake valve
CAUTION:
is installed properly
and brakes adjusted
correctly
beginning bleeding
procedures.
5. Stop engine and depress brake
pedal. Pedal should be hard, not
spongy, and fairly high. If pedal
is too spongy and/or travels too
far, repeat bleeding process.
6. It is a characteristic of the brake
valve to kick the pedal back when
actuated if system is not bled with
engine running.
HYDRAULIC
before
Courtesy of Crane.Market