MICO, Inc.
(4)
Form No. 81-460-044 Revised 2017-04-17
SERVICE CHECKS FOR HYDRAULIC SYSTEMS
BRAKES SLOW TO APPLY
1. No gas charge in accumulator
1. Check gas charge
2. Brakes not properly adjusted
2. Adjust brakes
3. Inoperative brakes
3. Check brakes
4. Hydraulic lines or fittings leaking
4. Check for leaks and repair
5. Pedal linkage out of adjustment
5. Adjust linkage
6. Inoperative automatic adjuster
(Goodrich Hi-torque Brakes only)
6. Check adjuster operation
7. Damaged hydraulic brake lines
7. Check lines for dents that restrict flow
of oil
BRAKES WILL NOT RELEASE
1. Pedal linkage out of adjustment or binding
1. Check for proper adjustment and
binding
2. Inoperative brakes
2. Check brakes
3. Inoperative automatic adjusters
3. Check operation of adjusters
4. Inoperative brake valve
4. Replace brake valve
INSUFFICIENT BRAKES
1. No oil or low oil level in tank
1. Check oil level in tank
2. Brakes not properly adjusted
2. Check brake adjustment
3. Oil or grease on brake lining
3. Clean or install new linings
4. Pedal linkage out of adjustment
4. Adjust linkage
5. Brake line damaged
5. Check lines and replace
6. Inoperative automatic adjuster
6. Check operation of adjusters
7. No gas charge in accumulator
7. Check gas charge
8. Inoperative brakes
8. Check brakes
9. Brake valve inoperative
9. Replace valve
BRAKES WILL NOT RELEASE
COMPLETELY
1. Brakes not properly adjusted
1. Adjust brakes
2. Inoperative brakes
2. Check brakes
2. Pedal linkage out of adjustment
3. Adjust pedal linkage
4. Inoperative wheel cylinders
4. Replace wheel cylinder
5. Inoperative automatic adjuster
5. Check operation of adjusters
6. Air in brakes (when automatic adjusters
used Goodrich Hi-torque Brakes only)
6. Bleed brakes
7. Inoperative brake valve
7. Replace brake valve
8. Back pressure on drain line too high
8. Remove restriction
EXCESSIVE BRAKING
1. Inoperative brakes
1. Check brakes
2. Inoperative brake valve
2. Replace brake valve
NO BRAKES
1. No oil in hydraulic system
1. Check oil level in tank
2. Pedal linkage out of adjustment
2. Adjust pedal linkage
3. Broken or damaged brake line
3. Check lines for breaks or damaged
condition
4. Brakes not properly adjusted
4. Adjust brakes
5. Inoperative system relief valve
5. Check pressure in pressure line to
valve
6. Worn pump
6. Check pressure in pressure line to
valve
7. Inoperative automatic adjuster
7. Check brake line pressure
8. Inoperative or worn brakes
8. Check brakes
9. Inoperative brake valve
9. Replace brake valve
ACCUMULATOR CHARGING CYCLE
REPEATS FREQUENTLY WHEN BRAKES
ARE NOT BEING USED
1. Leaking accumulator lines or fittings
1. Check lines and fittings for leaks and
correct
2. Accumulator gas charge too low
2. Check accumulator gas charge
3. Accumulator gas charge to high
3. Check accumulator gas charge
4. Inoperative brake valve
4. Replace valve
5. Line to accumulator plugged
5. Replace line
ACCUMULATOR STARTS TO CHARGE
BUT DOES NOT REACH HIGH LIMIT
1. No oil or low oil level in tank
1. Check oil level
2. Inoperative or worn pump (pump does not
deliver full flow or pressure)
2. Check pump pressure and flow
3. Inoperative system relief valve (valve
leaking or has low setting so full flow and
pressure are not available)
3. Check relief valve
4. Inoperative brake valve
4. Replace valve
ACCUMULATOR CHARGES FREQUENTLY
WHILE BRAKES ARE BEING HELD
1. Leaking brake lines or fittings
1. Check for leaks
2. Accumulator gas charge too low
2. Check accumulator gas charge
3. Accumulator gas charge too high
3. Check accumulator gas charge
4. Inoperative brake valve
4. Remove brake valve
INTERFERENCE WITH STEERING AT FULL
ENGINE THROTTLE BUT NOT AT IDLE
1. Inoperative brake valve
1. Replace brake valve
NO STEERING OR INADEQUATE STEER-
ING WHEN ACCUMULATOR IS CHARGING
BUT STEERING SATISFACTORY WHEN
ACCUMULATOR IS NOT CHARGING
1. Pump worn (not delivering full flow
or pressure)
1. Check pump pressure and flow
2. Relief valve inoperative (valve leaking so
that full flow and pressure not available)
2. Check relief valve
3. Inoperative brake valve
3. Replace brake valve
ACCUMULATOR CHARGING TIME
TOO LONG
1. No oil or low oil level in tank
1. Check oil level
2. Relief valve setting too low
2. Check valve setting
3. Pump worn or inoperative and not
delivering full flow or pressure
3. Check pump
4. Inoperative brake valve
4. Remove brake valve
ACCUMULATOR FAILS TO START
CHARGING
1. No oil or low oil level in tank
1. Check oil level
2. Worn or inoperative pump
2. Check pump pressure and flow
3. Inoperative relief valve
3. Check relief valve setting
4. Inoperative brake valve
4. Replace brake valve
VERY RAPID CYCLING OF CHARGING
VALVE
1. Accumulator gas charge too low
1. Check gas charge
2. Accumulator gas charge too high
2. Check gas charge
3. No gas charge in accumulator
3. Check gas charge
4. Inoperative brake valve
4. Replace brake valve
INTERFERENCE WITH OR NO STEERING
WITH ENGINE AT IDLE SPEED BUT
STEERING SATISFACTORY WITH ENGINE
AT FULL THROTTLE WITH THE ACCUMU-
LATOR CHARGING OR NOT CHARGING
1. Inoperative pump
1. Check pump pressure and delivery
2. Inoperative relief valve
2. Check relief valve setting
3. Inoperative steering system
3. Check steering system
BLEEDING PROCEDURE
Brake lines should be bled very carefully as soon as the valve is
installed in the machine. Air in the system will not allow the brakes to
properly release and may cause severe damage.
1. Start the engine and allow the accumulator to reach full charge.
Shut down the engine, then slowly apply and release the brakes,
waiting one minute between applications until brakes will not apply.
Repeat this step three times.
2. Operate the engine to maintain accumulator pressure to within
working limits throughout the bleeding procedure.
3. Open the bleeder screw at the wheel closest to the brake valve
and apply the brakes cautiously until all air is bled out of the line.
Then close the bleeder screw. Repeat this step at each wheel,
moving to the next closest wheel from the brake valve each time,
as follows: a. Left front b. Right front c. Right rear d. Left rear
4. Release brake pressure for at least 1 minute.
5. Apply the brakes, holding the pedal down for 10 seconds. Then
release the pressure for 1 minute. Repeat this step two more times.
6. Repeat step 3.
7. Check for system leaks and be sure of proper brake operation.
