Loader Bobcat 853, 853H. Manual - part 18

MAIN RELIEF VALVE (Cont’d)

Checking The Main Relief Valve Without Auxiliaries

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

MEL10003 – Hydraulic Tester
MEL10006 – Hydraulic Test Kit

Stop the engine.

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

Disconnect the hydraulic hoses (Item 1) [A] at the tilt
cylinder.

Connect the hydraulic tester to the tilt cylinder hoses [B].

Have a second person in the operator seat, with seat bar
in down position.

When an engine is running in an enclosed
area, fresh air must be added to avoid
concentration of exhaust fumes. If the engine
is stationary, vent the exhaust outside.
Exhaust fumes contain odorless, invisible
gases which can kill without warning.

W–2050–1285

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

I–2024–0284

Start the engine and run at idle RPM.

Push the tilt pedal at the top (toe) or bottom (heel) until
the hydraulic tester shows the correct fluid flow through
the flow meter.

Increase the engine RPM to maximum.

There should be 18.0 GPM (68,1 L/min.) free flow.

Turn the restrictor control, at the tester, to increase the
pressure until the main relief valve opens.

The correct pressure is 2700–2750 PSI (18617–18961
kPa).

If not, stop the engine.

Replace or adjust the main relief valve. (See Page 2–15.)

A

P–01187

1

853, 853H Loader

–2–21–

Service Manual

B

P–01193

MAIN RELIEF VALVE (Cont’d)

Removal And Installation

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

When making repairs on 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–2003–0284

The main relief valve (Item 1) [A] is located at the right
rear of the control valve.

Clean the area around the control valve.

Loosen and remove the main relief valve [B].

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

Remove the O–rings and back–up washers.

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

Install new O–rings and backup washers. Install the main
relief valve and tighten [A]. Check the pressure again.
(See Page 2–20.)

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

Loosen the locking nut (Item 2) [C].

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

Tighten the locking nut (Item 2) [C].

Reinstall the end cap (Item 1) [C].

NOTE: If the correct pressure can not be reached,

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

A

CD–11193

CD–15094

1

B

CD–15091

C

CD–15093

1

2

–2–22–

853, 853H Loader

Service Manual

DUAL PRESSURE MAIN RELIEF VALVE (S/N
512811001 & Above) W/ Select Valve (JEM)

Checking The Low Setting

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. Before 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 of the hydraulic tester to the female
quick coupler on the loader [A].

Connect the OUT port of the hydraulic tester to the male
quick coupler on the loader [A].

NOTE: Flow will be out from the female coupler on

the loader.

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

I–2024–0284

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, both lights
(Items 2 & 3) [B] will come ON.

NOTE: High horsepower switch should be in the

OFF position.

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 approximately 18.0 GPM (68,1 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 2700–2750 PSI (18617–18961 kPa).

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

If the relief pressure is not correct, stop the engine. Adjust
or replace the main relief valve. (See Page 2–26.)

A

P–05195

C

P–00387

P–00391

Left

Steering

Lever

Right

Steering

Lever

Control

Control

1

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.

853, 853H Loader

–2–23–

Service Manual

B

P–00998

2

1

3

DUAL PRESSURE MAIN RELIEF VALVE  (S/N

512811001 & Above) W/Select Valve (JEM) (Cont’d)

Checking The High Setting

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. Before 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 hydraulic tester to the auxiliary quick coupler

[A].

The IN port on the tester connects to the female coupler

on the loader.

The OUT port from the tester connects to the male

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.

Obtain a 3/8 inch (9,5 mm) I.D. hose (Item 1) [B] with a

3000 PSI (20685 kPa) rating or greater.

The hose loop (Item 1) [B] should be approximately of 28

inches (711 mm) in length (including quick couplers).

A small male coupler (Item 2) [B] is needed for one end

of the hose, and a small female coupler (Item 3) [B] is

needed for the other end of the hose.

Use the correct fittings and O–rings to connect the

couplers to the hose.

Drill orifice (Item 1) [C] size to 0.070 inch (1,8 mm). Install

the threaded orifice (Item 1) [C] in the male coupler (Item

2) [C] and install the coupler on the fitting.

A

P–05195

C

P–04757

2

1

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853, 853H Loader

Service Manual

B

P–04717

3

1

2