4-13. TROUBLESHOOTING (CONT)
TEST OR INSPECTION
HYDRAULIC SYSTEM - CONT
EXCESSIVE PUMP NOISE OR PUMP FAILURE
Check that hydraulic tank shut-off valve is open (para. 2-4).
If APU has run longer than 30 seconds, with the hydraulic tank shut-off valve
closed, pump may be damage and the hydraulic system, including filters, may be
contaminated with metal particles.
a. If hydraulic tank shut-off valve was closed with APU running, check hydraulic filter indicator (para.
to determine how much contamination has moved away from hydraulic pump.
clogged, contamination has not reached filter. Remove filter supply line, filter assembly, and
supply hoses from pump, gooseneck, and step assembly. Remove and replace pump (para.
4-76). Clean all fittings, hoses, and filter parts. Replace all parts
b. If contamination has clogged filter, some contamination may have passed filter and moved into
hydraulic system. Refer to hydraulic flushing procedure (para. 4-20) and flush hydraulic system.
Check that hydraulic system will maintain proper operating pressure.
Refer to symptom 18, steps 3, 4, and 5 for hydraulic failures.
PLATFORM SUSPENSION WILL NOT ADJUST OR ADJUSTMENTS ARE SLUGGISH
Check for general hydraulic failures.
Refer to symptom 16 for general hydraulic failures.
Check for external leaks at hydraulic fittings/joints.
Refer to symptom 16 to continue checking for external leaks.