3-24
To determine whether the problem is in the left or right-hand cylinder, put a pressure gauge with
a range of at least 5000 PSI (350bar) on the ¼” size port on the side of one of the holding
valves.
W A R N I N G
Disconnecting the RCL hose from a single holding valve may cause the boom to lower if
the other holding valve is faulty. Ensure that the boom is fully lowered or blocked before
disconnecting the hose.
N O T I C E
The RCL will not function properly with one hose disconnected from a cylinder.
BMC uses multiple RCL models. If your crane has hoses connecting the cylinder to the RCL
computer, the cylinders are hydraulically connected. They must be isolated for the following
procedure. Fully lower the boom. Isolate the cylinders from each other by disconnecting the
piston and rod side RCL hoses from one cylinder. Cap the hoses and plug the hole in the hold-
ing valve. Note that the caps and plugs will experience full system pressure, and adequate care
must be taken to ensure the caps and plugs are properly installed. Note the RCL will not func-
tion properly with one cylinder disconnected.
With rated load on the hook, the boom over the front, and outriggers set, record the pressure on
the gauge while slowly raising the boom tip about three feet (1 m) above its horizontal position.
Then return the boom control lever to neutral and record the pressure. Then turn the engine off,
push the BOOM lever to the LOWER position and record the pressure on the gauge. Repeat on
the other holding valve. If the pressure to hold the load is lower at one valve than the other, the
lower pressure side is the problem side.
Try to raise the pressure in the problem side to match the pressure on the other valve by tight-
ening the adjusting screw on the holding valve after removing the adjustment cover and loosen-
ing the lock nut.
If adjusting the holding valve does not fix the problem, continue troubleshooting. Lower the
boom fully, turn off the engine and push the BOOM lever to the full LOWER position. Switch the
holding valves from left-hand to right-hand and vice-versa. Repeat the pressure tests. If the
problem side changes, the holding valve is at fault; if the problem side is the same, then the pis-
ton seal is leaking.
After the problem has been solved, remember that twin lift cylinders must have matched set-
tings on holding valves. If RCL hoses were disconnected, reconnect them. Bleed the hoses
per instructions on page 3-20.
TELESCOPE CYLINDER HOLDING VALVE
A holding valve is directly connected to the base of the telescope cylinder rod. The valve is de-
signed to hold the boom in position should loss of power or pressure line failure occur.
The holding valve should be checked with the boom elevated to the maximum angle and the
boom extended to a 6-foot load radius. A 36,000-pound (16330kg)
load on a 4-part line is
required for this test.
Use the hoist to lift this load about 6 inches (15cm) above the ground.
The radius of the test load should be within the rating on the capacity chart. Use great care to
prevent the load from hitting the crane.
Turn the engine off and pull the TELESCOPE lever to the RETRACT position. If the boom re-
tracts, the valve should be adjusted.
To adjust the holding valve, loosen the lock nut on the adjusting screw and tighten screw until
unpowered movement stops. Retighten the lock nut to hold the proper adjustment.
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