Loader Bobcat 773. Service Manual - part 32

MAIN RELIEF VALVE

Checking

The tools listed will be needed to do the following
procedure:

MEL10003 – Hydraulic Tester
MEL10006 – Hydraulic Test Kit

Turn the key switch to the OFF position, as the engine
stops running, turn the key switch all the way to the left to
release the hydraulic pressure at the front auxiliary quick
couplers.

Lift and block the loader. (See Page 1–1.)

Connect the IN port (Item 1) [A] of the hydraulic tester to
the bottom (female) quick coupler on the loader.

Connect the OUT port (Item 2) [A] of the hydraulic tester
to the top (male) quick coupler on the loader.

The hydraulic tester must be in the fully open
position before you start the engine.

I–2024–0284

W–2017–0286

Put jackstands under the front axles and rear
corners of the frame before running the engine
for service. Failure to use jackstands can allow
the machine to fall or move and cause injury or
death.

Start the engine and run at low idle RPM. Push the mode
switch (Item 1) [B] twice (on the instrument panel) to
engage the front auxiliary hydraulics detent, the lights
(Items 2 & 3) [B] will come ON.

Push the button (Item 1) [C] for fluid flow to the quick
couplers.

Watch the flow meter on the hydraulic tester to make sure
the flow is correct. Increase the engine speed to full RPM.

There should be 15 GPM (56 L/min.) free flow. Turn the
restrictor control, on the tester, until the main relief valve
opens. The correct pressure for the main relief is 3000
PSI (20600 kPa).

Push the button (Item 1) [C] to disengage the detent
position to the front quick couplers.

If the relief valve pressure is not correct, stop the engine.
Adjust (See Page 2–75) or replace the main relief valve.
(See Page 2–62.)

Revised Jan. 99

P–04343

P–02152

Right

Steering

Lever

Control

(Optional)

W–2006–0284

When the engine is running during service, the
steering levers must be in neutral and the
parking brake engaged. Failure to do so can
cause injury or death.

–2–74–

773 BICS Loader

Service Manual

P–03272

MAIN RELEIF VALVE (Cont’d)

Adjustment

If the pressure is not correct, adjust the main relief valve.
Remove the end cap (Item 1) [A].

Turn the adjusting screw in or out until the pressure is
correct.

NOTE: The control panel and lift lock valve have

been removed for clarity only. They do not
need to the removed for this main relief valve
removal and installation procedure.

NOTE: If the correct pressure can not be reached,

replace the main relief valve. Check the
pressure setting of the new relief valve.

Removal and Installation

Raise the operator cab. (See Page 1–1.)

Clean the area around the control valve. Loosen and
remove the main relief valve (Item 1) [B].

Remove the O–rings and back–up washers [A].

Clean the main relief valve in clean solvent. Use air
pressure to dry the valve.

Install new O–rings and back–up washers. Install the
main relief valve (Item 1) [B] and tighten. Check the
pressure again. (See Page 2–74.)

Installation: Tighten the main relief valve to 35–40
ft.–lbs. (47–54 Nm) torque.

NOTE: The valves may appear to be different, but the

procedure is the same.

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.

I–2003–0888

Revised Jan. 99

P–04178

773 BICS Loader

–2–75–

Service Manual

773 Service Manual #6900092–Hydraulic System Section Part 3 of 4

B–06764

Back–up

O–ring

HYDRAULIC PUMP

Removal And Installation

Stop the engine. Move the hydraulic controls to release
the hydraulic pressure.

Raise the seat bar.

Lift and block the rear of the loader. (See Page 1–1.)

Raise the operator cab. (See Page 1–1.)

Remove the tilt lock valve. (See Page 8–1.) (Earlier
models only.)

NOTE: Also disconnect the pilot pressure hose (not

shown) from the pump outlet fitting if the
loader has optional rear auxiliary hydraulics.

Disconnect the hydraulic pump outlet hose (Item 4) [C]
from the outlet fitting.

Drain the hydraulic fluid (using the case drain hose) from
the reservoir into a clean container.

Disconnect the hydraulic pump inlet hose (Item 1) [B]
from the reservoir and drain as much fluid from the hose
as possible. Reconnect the hose to the reservoir.

Disconnect the inlet hose (Item 1) [C] from the hydraulic
pump (Item 2) [C].

Disconnect the hose (Item 3) [C] (which is routed to the
tilt lock valve), from the side of the hydraulic pump outlet
fitting on earlier machines only.

NOTE: Photo’s may appear different but the

procedure is the same.

Revised Jan 99

Disconnect the case drain hose (Item 1) [A] from the main
control valve.

Never work on a machine with the lift arms up
unless the lift arms are secured by an approved
lift arm support device. Failure to use an
approved lift arm support device can allow the
lift arms or attachment to fall and cause injury
or death.

W–2059–0598

Raise the lift arms and install an approved lift arm support
device. (See Page 1–1.)

P–11779

P–04136

I–2003–0888

–2–76–

773 BICS Loader

Service Manual

N–00809

HYDRAULIC PUMP (Cont’d)

Removal And Installation (Cont’d)

Remove the two mounting bolts (Item 1) [A] from the
hydraulic pump with a 5/16 inch allen wrench.

Always clean up spilled fuel or oil. Keep heat,
flames, sparks or lighted tobacco away from
fuel and oil. Failure to use care around
combustibles can cause explosion or fire
which can result in injury or death.

W–2103–1285

See Page 2–80 for the proper Disassembly and
Assembly procedures.

Remove the coupler (Item 1) [B] from the hydraulic pump
shaft.

Remove the large O–ring (Item 2) [B].

Installation: Use a new O–ring when installing the
hydraulic pump.

NOTE: The allen wrench will need to be modified for

the procedure.

Installation: Tighten the mounting bolts to 27–37 in.–lbs.
(37–50 Nm) torque.

Remove the hydraulic pump from the hydrostatic pump.

Revised Jan 99

P–04283

P–04133

773 BICS Loader

–2–77–

Service Manual

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