New Holland CX720 Repair Manual page 2536

TRANSMISSION Hydrostatic - Troubleshooting (C.20.F - G.40.A.10)
Problem
Machine will not operate
in either direction
Combine does not move
when hydrostatic control
lever is moved.
Hard to select a
transmission gear, or
will not go into gear
Neutral is difficult or
impossible to find
Ground travel speed
erratic
Ground speed or combine
erratic and loses power.
Also seems to lack power
Oil temperature too high
System noisy
POWER TRAIN - TRANSMISSION Hydrostatic
Possible Cause
Control cable not connected
Low hydrostatic oil
Air in system
Exceeding relief valve pressure
Drive system unable to build up pressure
Charge pressure relief valve is stuck open Repair charge pressure relief valve.
Transmission gear selector in neutral
Selected transmission gear too high to
move combine activating pressure over-
ride
Reservoir oil level very low
Air in system (may be due to low oil level) Purge air from system.
Hydrostatic lines leaking
Blocked hydrostatic filter
Hydrostatic pump not in neutral though hy-
drostatic control lever is in neutral
Hydrostatic lever out of calibration
Oil level low
Blocked oil filter element
Exceeding relief valve pressure
Unable to maintain charge pressure
Cold or low oil supply
Reservoir oil level low
Hydraulic lines leaking
Blocked hydrostatic filter
Internal leaks or malfunction in pump or
motor
Low oil level
Blocked oil cooler
Blocked inlet filter
System pressure too high, relief valve con-
tinually blowing
Air in system
Connect control cable
Check and fill the reservoir to the correct oil
level. Use specified oil only.
Locate and repair leak
Shift to lower gear
Air in system. Air will also cause the system
to be noisy. Check all fittings, especially
around the filter, in the suction line and lo-
cate the point or points where air is being
drawn into the system. Tighten fittings and
joints where air leaks exist. Replace seal
where necessary.
Select required gear
Change to lower gear
Check and fill the reservoir to the correct oil
level. Used specified oil only
Check, tighten or replace as necessary
Check and replace filter element as neces-
sary
Readjust control cable
Readjust control cable
Check for leaks and repair as necessary
Change filter element
Shift to lower gear. Repair or replace relief
valve.
The charge pressure relief valve is dam-
aged or stuck open. Internal damage to
pump or motor
Check oil levels. Allow oil to warm.
Check and fill the reservoir to the correct oil
level. Used specified oil only.
Check level, fill as necessary
Check and replace filter element as neces-
sary
Pressure test system, repair or replace mo-
tor or pump as required.
Fill to correct level and check for leaks
Clean / replace as required
Replace filter
Pressure test system, inspect multi function
valves
Check and fill the reservoir to the correct oil
level. Use specified oil only
2 4/7/2006
C.20.F / 84
Correction