Service Manual

23
Principles of Hydraulic Test Equipment
A hydraulic system with an excessive increase in
heat or noise is a potential failure. Should either of
these conditions be noticed, immediately stop the
machine, turn off the engine, locate the cause of
the trouble, and correct it before allowing the ma-
chine to be used again. Continued use of an im-
properly functioning hydraulic system could lead to
extensive internal damage.
When troubleshooting a hydraulic problem:
1. Know the hydraulic system for the machine:
• Study the schematics, Operators Manual and
Service Manual.
• Know how the system works and what the re-
lief valve setting and the pump output should
be.
2. Talk to the operator:
• How did the machine act just as it started to
malfunction?
• Was any “do-it-yourself” service performed or
did anyone else attempt to repair the ma-
chine?
• How was the machine used and when was
maintenance last performed?
3. Operate the machine:
• Operate the machine in conditions simulating
when the malfunction occurred. Verify what
the operator described.
• Are the gauges and warning lights operating
correctly.
• Do the controls feel spongy or stick.
• Check for any unusual sounds, smells, or
smoke. At what speed or operating cycles
does this occur.
4. Inspect the machine:
• Check the hydraulic fluid level and condition.
Is the fluid dirty or filters plugged?
• Check for overheating. Does the oil have a
burnt odor? Is the oil cooler plugged or lines
caked with dirt?
• Look for bent or collapsed fluid lines. Check
for leaks, loose fasteners, cracked welds,
binding pivot points, damaged linkage, etc.
5. List possible causes:
• Note what was reported by the operator and
verified by you.
• List what you found during your inspection.
• Remember that there may be more than one
cause leading to the failure or malfunction.
6. Determine which cause is most likely the problem:
• Look at your list of most possible causes and
determine which are the most likely. Use the
troubleshooting charts in the Service Manual.
7. Test your findings
• Operate the machine with a hydraulic tester
connected to the suspected malfunctioning
circuit.
• It may be necessary to replace or adjust a
component to verify your findings.
Figure 1
Figure 2
Figure 3