Loader Bobcat 853, 853H. Manual - part 14

PUMP CAPACITY:

        18.0 GPM (68,1 L/min.)

HI FLOW CAPACITY: (Includes      )

       24.0 GPM (90,8 L/ min.)

at 2750 RPM

 C apacity  . . . 16.0 Qts  (15,1 L)

DISPLACEMENT CONTROL VALVE

     N eutral  . . . . 310-330 PSI

               (2137-2275  kPa)

    Stroked . . . . 3O0-320 PSI

               (2069-2206 kPa)

HYDRAULIC PUMP

              . . . .Gear Type

           290 PSI (2000  kPa)

FLOW DIVIDER ADJUSTMENT VALVE

NOTE: Unless otherwise specified

      springs have NO significant

      pressure value.

HI-FLOW MACHINE

PILOT ACTIVATED DIRECTIONAL

  CONTROL VALVE - FLOW CONTROL

  SPOOL

FIXED CAPACITY DISPLACEMENT

  BIDIRECTIONAL HYDROSTATIC

  MOTOR

LEGEND

RESERVOIR:

DIFFERENTIAL PRESSURE SWITCH:

SPRING LOADED FILTER BYPASS

ONE WAY RESTRICTOR VALVE

Printed in U.S.A.

DRIVE MOTOR SHUTTLE VALVE

RELIEF/REPLENISHING VALVE - HIGH

RELIEF VALVE - MAIN:

RELIEF VALVE - PORT:

CHECK VALVE - BUCKET POSITION

  VALVE

           3500 PSI (24132 kPa)

SOLENOID ACTIVATED DIRECTIONAL

  CONTROL VALVE - AUXILIARY

LOAD CHECK VALVE

PILOT ACTIVATED DIRECTIONAL

  CONTROL VALVE - UNLOADING

  SPOOL

SHUTTLE RELIEF VALVE:

       36-44 PSI (248-303 kPa)

1

at Front Quick Couplers

853 (S/N 512811001-15999 WITH JEM AUXILIARY VALVE)

MC2399LU (5-19-99)

2

4

3

5

10

 VALVE: 45-55 PSI (311-379 kPa)

6

7

14

13

15

12

9

25

19

20

22

17

16

RELIEF VALVE - CHARGE:

38

31

(Printed June 1999)

PRESSURE:

35 FILTER - HYDROSTATIC (CANISTER)

8 RELIEF VALVE - PORT:  (OPTIONAL)

           2500 PSI (17238 kPa)

       2500 PSI (17238 kPa)

11 RELIEF/ANTICAVITATION VALVE -

PORT (TILT BASE END) (OPTIONAL)

TOW VALVE

18

OPTIONAL  . 5000 PSI (34475 kPa)

24

26 MUFFLER (If Equipped)

CHARGE PRESSURE SENSOR

27

28 FLUID TEMPERATURE SENSOR

29

SOLENOID ACTIVATED DIRECTIONAL

  CONTROL VALVE - FRONT

  AUXILIARY

30

34

36 FILTER - HYDRAULIC (CANISTER)

37

FILTER

COLD OIL BYPASS VALVE

39 ANTICAVITATION VALVE

SOLENOID ACTIVATED DIRECTIONAL

  CONTROL VALVE (TWO COIL)

PILOT TO OPEN CHECK VALVE

40

32 RESTRICTION

SYSTEM MAIN RELIEF:

          2800 PSI (19306 kPa)

HI FLOW MAIN RELIEF:

          3300 PSI (22754  kPa)

STANDARD . 4350 PSI (29990 kPa)

at  1150 PSI (7929 kPa)

RELIEF VALVE - MAIN HIGH FLOW

         3000 PSI (20685 kPa)

33 SOLENOID ACTIVATED DIRECTIONAL

  CONTROL VALVE

B.O.S.S. L oader - Normally Closed

Standard Loader - Normally Open

140°F. (60°C.) Fluid at Full RPM

CHECK VALVE - FILTER

HYDRAULIC/HYDROSTATIC SCHEMATIC

21 AUXILIARY HYDRAULIC PUMP:

at  1150 PSI (7929 kPa)

at  2750 RPM

         6.0 GPM (22,7 L/ min.)

23 CHARGE PUMP .  14.0-15.0 GPM

(52,9-56,7 L/ min.)  at  2700 RPM

FILTER

MC2399LU

23

MC2399U (5-19-99)

WORKING CIRCUITS

PILOT PRESSURE

DRAIN CIRCUITS

COMPONENTS

RIGHT DRIVE MOTOR

BUCKET POSITION VALVE (OPTIONAL)

HYDRAULIC

CONTROL

VALVE

FRONT AUXILIARY

OIL

COOLER

D

C

A

B

HYDROSTATIC

FILTER

HYDRAULIC

FILTER

HYDROSTATIC PUMPS

T1LT CYLINDER

LIFT CYLINDER

LEFT DRIVE MOTOR

2

AUXILIARY

SPOOL

TILT CYLINDER

SPOOL

LIFT CYLINDER SPOOL

11

INLET

INLET

OUTLET

OUTLET

1

35

3

26

24

2

3

36

4

40

16

17

16

17

38

38

18

19

19

20

20

22

21

25

8

9

13

13

12

39

5

6

7

10

10

14

AUXILIARY VALVE (JEM)

FRONT AUXILIARY

D1

D2

F1

F2

FEMALE

MALE

FEMALE

MALE

9

15

CASE DRAIN

23

29

29

32

32

34

30

33

31

27

28

PORT

BLOCK

37

Printed in U.S.A.

TROUBLESHOOTING

Chart

The following troubleshooting chart is provided for
assistance in locating and correcting problems which are
most common. Many of the recommended procedures
must be done by authorized Bobcat Service Personnel
only.

W–2004–1285

Check for correct function after adjustments,
repairs or service. Failure to make correct
repairs or adjustments can cause injury or
death.

The hydraulic system will not operate.

1, 2, 3, 5

The transmission warning light comes ON when hydraulics are
  operating. (853 Base)

1, 3

Slow hydraulic system action.

1, 3, 4, 5, 6, 8

Hydraulic action is not smooth.

1, 4, 5, 6, 7

Lift arms go up slowly at full engine RPM.

1, 3, 4, 5, 6, 7, 8, 9

The lift arms or Bob–Tach will move the pedal in neutral position.

4

The lift arms come down with the pedal in the neutral position.

4, 9, 10, 11

PROBLEM

CAUSE

KEY TO CORRECT THE CAUSE

  1.

The fluid level is not correct.

  2.

The pedal linkage is disconnected.

  3.

The hydraulic pump has damage.

  4.

The pedal linkage is not adjusted correctly.

  5.

Relief valve is not at the correct pressure.

  6.

Suction leak on the inlet side of the hydraulic pump.

  7.

Fluid is cold. Wrong viscosity fluid. (See Section 9.)

  8.

Using the loader for more than its rated capacity.

  9.

Internal leak in the lift cylinder(s).

10.

External leak from the lift cylinder(s).

11.

Damaged lift spool.

853, 853H Loader

–2–7–

Service Manual

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

Tighten Procedures

For tightening torques for hydraulic fittings,
tubelines etc., See Section 9. – Hydraulic Connection
Specifications.

HYDRAULIC SYSTEM INFORMATION

Hydraulic fluid escaping under pressure can
have sufficient force to enter a person’s body
by penetrating the skin. This can cause serious
injury and possibly death if proper medical
treatment by a physician familiar with this
injury is not received immediately.

W–2145–0290

–2–8–

853, 853H Loader

Service Manual