Bobcat 741 - Page 74

HYDROSTATIC SYSTEM INFORMATION
IMPORTANT
When repairing hydrostatic and hydraulic
systems, clean the work area before
disassembly and keep all
parts clean. Always
use caps and
plugs on hoses, tubelines and
ports
to keep dirt out. Dirt can quickly damage
the system.
1-2003-0888
High Pressure RelieflReplenishing Valve Function
The valves for forward movement are different from the
valves for reverse
travel.
The high pressure relief/replenishing valves for forward
travel,
also release very high pressure.
The functions of the replenishing valves are:
1.
To give replacement fluid to the low pressure side of
the hydrostatic circuit. Replacement
fluid is needed
because of normal internal leakage and the
controlled flow to the oil cooler for cooling; Function
1
[A] and Function 1 [B].
2.
To keep high pressure fluid out of the low pressure
side of the hydrostatic circuitry; Function 2
[A] and
Function 2 [B].
3.
To release high pressure caused by moving forward
with a heavy
load on the loader, Function 3 [A].
-3-2-
A
CHARGE OIL
~ ~
FUNCTION 1 + •
FUNCTION 2
Valve Moves for Charge
Oil Replacement
Valve
Stays on Seat to
Hold High Pressure for Drive
FUNcno;'~
8
FUNCTION 1
FUNCTION 2
Valve Release Very High
Pressure to Protect System
I B-02805
Valve Moves for Charge
Oil Replacement
Valve
Stays on Seat to
Hold High Pressure for Drive
741,742,743, 743DS Bobcat Loader
Service Manual