Case 435 - Charge Pump - Pressure Test (A.10.A.21 - F.40.A.30); 435, 445, 445 Ct

DISTRIBUTION SYSTEMS - PRIMARY HYDRAULIC POWER SYSTEM
Charge pump - Pressure test (A.10.A.21 - F.40.A.30)
435, 445, 445CT
Testing the low-pressure charge system is safer and usually more informative than going into the high-pressure
test ports. To obtain as much system information as possible, charge pressure readings must be taken in neutral
as well as working the system in both the forward and reverse directions.
With the system in neutral, only charge pressure is present in the closed loop. At this time, the leakage from the
system is the least and the charge pressure is the highest. As the system is pressurized, the leakage from the
system w ill increase and the charge pump flow will make up for this leakage. With more of the charge pump oil
flowing to the closed loop, less oil will flow across the charge pressure relief valve, and therefore the pressure will
be slightly less. If the leakage from the system is excessive, the charge pressure will drop off more. This slight
drop in charge pressure between the system in neutral and with the system under load indicates the condition
of the closed loop system components.
1. Raise and securely block the unit off the ground.
2. Remove the brake assist line from the tee fitting at
the T port (1
) of the brake v alve (3).
BD03F001_1 1
3. Remove the cap from the tee fitting on the P port
(2) o f the brake valve (3).
4. Connect the removed brake assist line to the tee
fitting on the P port (2) of the brake valve (3).
5. Ca p the tee fittingontheTport(1)ofthebrake
valve (3).
6. Remove the brake release line from the tee fitting
that connec ts to the C2 port (4) of t he brake valve
(3).
BD03F001_2 2
7. Cap the tee fitting that connects to the C2 port (4) of
the brake valve (3).
8. Connect a 4,137 kPa (41 bar) (600 psi) pressure
ga
uge to the charge pressure test port.
A. For units without high flow, remove the cap
from the tee fitting and install a 4,137 kPa(600 psi)
pr
essure gauge.
B. For units with high flow, remove the hose from the
tee fitting and install a 4,137 kPa(600 psi) pressure
ga
uge.
1 04/05/2005
A.10.A / 49