Hyundai HL955 Manual page 515

Problem
Hydraulic oil foams
Remote control valve
(RCV) leaking
※
Followings are general precautions for the hydraulic system and equipment.
1) Every structure has its limit of strength and durability. The relief valve is installed to limit the
pressure on the hydraulic equipment and protect various parts of the wheel loader from possible
damage. Therefore, never change the preset pressure of the relief valve unless absolutely
necessary.
2) Since the hydraulic equipment is built with precision, the presence of only the slightest amount of
dust and / or other particles in the hydraulic circuit might cause wear and/or damage, resulting in
unstable functions and/or damage, resulting in unstable functions and/or unexpected accidents.
Therefore, always keep hydraulic oil clean. Periodically, check the filter in the return circuit and
replace the element as necessary.
3) Extract about 200cc of hydraulic oil from the tank as a sample every 6 months. If possible, have it
analyzed by a specialist to confirm that the oil can still be used. Never extract the oil for sampling
until the oil temperature has become the normal operating temperature. Since the replacement
period varies depending on operating conditions, refer to Operator's Manual and change oil.
4) Should the equipment get damaged due to the presence of metal particles and/or foreign matter in
the circuit drain out the hydraulic oil and carry out flushing. Also, replace the filter element and
clean the hydraulic tank. Change the hydraulic oil entirely.
5) When checking the filter, if found metal particles in the element, drain out the hydraulic oil entirely,
flush the whole circuit, and then fill with new oil. The presence of metal particles may indicate
internal damage to the equipment. In such a case, check carefully before flushing, and repair or
replace as required.
6) To add and/or change the hydraulic oil, always use recommended oil. (Refer to the list of
recommended oils and lubricants at page 1-22, Recommended lubricants.) Never mix oil of
different makes of kinds.
7) To change the hydraulic oil, use a clean vessel and funnel for pouring it into the tank. Never use
cloth because it might cause the presence of lint in the circuit.
8) When removing the hydraulic equipment, be sure to put plugs or caps on hoses, tube lines and
ports. Also, enter mating marks for later identification.
Cause
Low oil level.
Wrong oil.
Water in oil.
Loose or faulty suction lines (air leak in
system).
Leaking plunger seals.
6-50
Remedy
Add recommended oil.
Change to recommended oil.
Change oil.
Tighten or install new lines.
Remove, inspect and replace plunger
seals.