Boom Extend Cylinder Binding.
BOOM EXTEND CYLINDER EXTENDS BUT WILL NOT RETRACT
Counterbalance Valve Malfunctioning.
Internal Leakage in Boom Extend Cylinder.
BOOM SECTION RETRACTS UNDER LOAD
Boom Section Retracts Under Load.
With boom off to one side and horizontal, extend boom approximately 6 ft (1.83 m). Mark side of
the extended section at end of the boom base.
Elevate boom to maximum angle and suspend a 5 ton (4.54 metric ton) load on a two-part line
1 ft (305 mm) off ground.
With engine shut off, hold or tie boom extend lever in fully extended position for approximately
Return boom extend lever to neutral position. Start engine and lower boom to horizontal. Re-mark
extended section as in Step 1. Measure distance between marks. The difference is the leak-down:
Leak-down must not exceed 0.75 inch (19.1 mm) in 15 minutes with hydraulic oil at a working
temperature. If leak-down exceeds 0.75 inch (19.1 mm) in 15 minutes, perform Step 5.