© Bosch Automotive Service Solutions LLC
Sheet No.
Issue Date: Rev. B, April 28, 2014
Parts List & Operating Instructions Form No. 570918
Preventive Maintenance
Important: The greatest single cause of failure in hydraulic units is dirt. Keep the under axle jack clean
and well lubricated to prevent foreign matter from entering the system. If the jack has been exposed
to rain, snow, sand, or grit, it must be cleaned before it is used.
1. Store the jack in a well-protected area where it will not be exposed to corrosive vapors, abrasive dust, or
any other harmful elements.
2. Regularly lubricate the moving parts.
3. Replace the oil in the reservoir at least once per year. To check the oil level, disconnect the air supply, place
theunderaxlejackonlevelground,andcompletelyretracttheram.Removethellerplug/dipstick,wipe
it clean, and reinstall it, threading it in all the way. Remove the dipstick again and note the oil level. The oil
level should be between the two marks on the dipstick. Add or remove approved anti-wear hydraulic jack
oil as needed, and install the dipstick. CAUTION: The use of alcohol, hydraulic brake uid, detergent
motor oil, or transmission oil could damage the seals and result in jack failure.
4. Inspect the jack before each use. Take corrective action if any of the following problems are found:
a. Cracked or damaged housing d. Scored or damaged piston rod
b. Excessive wear, bending, or other damage e. Loose hardware
c.Leakinghydraulicuid f.Modiedoralteredequipment
Troubleshooting Guide
Repairproceduresmustbeperformedinadirt-freeenvironmentbyqualiedpersonnelwhoarefamiliar
with this equipment.
Trouble Cause Solution
Erratic action 1. Air in system.
2. Oil viscosity too high.
3. Internal leakage in cylinder.
4. Cylinder sticking or binding.
1. Follow the instructions in this document, "Bleeding
Air from the Under Axle Jack".
2. Change to a lower viscosity oil.
3. Replace worn packings. Look for excessive
contamination or wear.
4. Look for dirt, gummy deposits, or leaks. Check for
misalignment, worn parts, or defective packings.
Jack does not lift 1. Low / no oil in reservoir.
2. Air-locked system.
3. Load is above capacity of jack.
4. Delivery valve and / or bypass valve not
working correctly.
5. Packing worn out or defective.
1. Fill with oil and bleed system.
2. Follow the instructions in this document, "Bleeding
Air from the Under Axle Jack".
3. Use correct equipment.
4. Clean to remove dirt or foreign matter. Replace oil.
5. Replace power unit.
Jack lifts only partially 1. Not enough oil. 1. Check oil level.
Jack advances slowly 1. Low air pressure.
2. Seals are leaking.
3. Pump not working correctly.
1. Adjust air pressure to 90–175 psi.
2. Take jack to OTC authorized service center for repair.
3. Take jack to OTC authorized service center for repair.
Jack lifts load, but does not hold 1. Cylinder packing is leaking.
2. Valve not working correctly (delivery,
release, or bypass).
3. Air-locked system.
1. Replace seals.
2. Take jack to OTC authorized service center for repair.
3. Bleed system.
Jack leaks oil 1. Worn or damaged seals. 1. Take jack to OTC authorized service center for repair.
Jack will not retract 1. Release valve is closed. 1. Open or clean release valve.
Jack retracts slowly 1. Cylinder damaged internally. 1. Take jack to OTC authorized service center for repair.
Sound of air leaking when lever is
in retract position.
1. This is normal.
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