Lull 6K Service Manual - Manual (Page 178)

Supply, Pressure, and Return Hydraulics
5-34 Service Manual — Models 644B, 6K, 844C, 8K, 1044C, 10K
Troubleshooting Pump Problems
Problem Probable Cause Solution
1. Excessive pump noise A. Low oil level in the hydraulic
reservoir
Fill reservoir to proper level with the recommended
hydraulic fluid. DO NOT overfill.
B. Air in the system 1. Operate hydraulic system until purged.
2. Check inlet (suction) lines and fittings for air
leaks.
C. Vacuum condition 1. Check inlet (suction) lines and fittings for
restrictions.
2. Check reservoir breather filter conditions.
D. Oil too thick Be certain correct type of oil is used for refilling or
adding to the system. Viscosity must be correct for
ambient temperatures.
E. Cold weather Run hydraulic system until unit is warm to the
touch and noise disappears. Check oil viscosity.
2. Pump Overheating A. Internal leakage Return vehicle to maintenance shop for evaluation
and repair.
B. Low fluid level Add oil to operating level.
3. System not developing
pressure
A. Relief valve open Replace or repair the relief valve.
B. Loss of fluid internally
(slippage)
Return the vehicle to the maintenance shop for
repair of hydraulic system.
C. Disconnected or broken pump
drive
Inspect and repair or replace.
4. Loss of fluid A. Ruptured hydraulic lines
B. Loose fittings
C. Leaking gaskets or seals in
pump or circuit
1. Check all external connections, tubing, and
hoses. Tighten connections and replace any
ruptured tubes or hoses.
2. Observe mating sections of pump for leaks.
3. Replace seals or gaskets if possible.