Husqvarna PT26D Workshop Manual page 135

Flow test flushing valve
The flow Q2 is dependent on the opening
pressure for the flushing valve's pressure lim-
iting valve. Measuring Q2 provides the flow
for the transmission oil in the drive wheel cir-
cuit from the flushing valve. This is an impor-
tant test when suspecting that the hydraulic
system is running too hot. When the flow test
is OK, the flushing valve's pressure limiting
switch below does not need to be checked. If,
however, Q2 is defective, first check the
flushing valve's pressure limiting switch as
described below. Incorrectly connected
cables to the drive system's valve block also
lead to overheating of the system.
Jack up and block the machine
Disconnect and plug the fuel hose from the
flushing valve. Connect a nipple, thread 9/16"
UNF-18 with a hose, to the fuel hose's port
on the flushing valve and lead the hose to a
suitable measuring vessel.
Plug the disconnected hose with a steel plug.
Drive full speed ahead with the machine
jacked up. The flow should be 7.5 l/min. Thus
drive 20 s and multiply by 3 = 2.5 litres oil.
Drained oil must not be refilled, but should be
treated as waste oil.
Flushing valve pressure limiting
switch
This test is not necessary when the flow test
Q2 is OK.
Connect manometer 0-2.5 MPa (0-25 bar) to
measuring point P5 on the flushing valve,
thread 9/16" UNF-18. The plug is hard to
reach unless you temporarily disconnect one
of the hoses connected to both sides of the
plug.
Pressure 1.4-1.5 MPa (14-15 bar) should
show when the axial piston pump is set to full
capacity and the engine is running at high
speed.
134
English-
TROUBLE SHOOTING
Test socket for flow measurement Q2.
Test socket P5 and pressure limiting switch
Q2
8043-188
P5
Pressure limiting
valve
8043-188