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JCB 3CX, 4CX, 214e, 214, 215, 217 & VARIANTS Backhoe Loader. Service Manual - page 16

Section E

Hydraulics

Section E

20 - 1

Service Procedures

20 - 1

Hydraulic Contamination

Hydraulic Fluid Quality

Contaminant Standards

Construction machinery uses a large volume of fluid in the

Dirt that damages your system is in many cases too small to

hydraulic system for power transmission, equipment

be seen with the eye. The particle size is measured in

lubrication, rust prevention and sealing.

microns.

According to a survey conducted by a pump manufacturer,

1 micron=

0.001 mm (0.0000394 in)

seventy per cent of the causes of problems in hydraulic

equipment were attributable to inadequate maintenance of

Listed below are a few typical comparisons:-

the quality of the hydraulic fluid.

Red Blood Cell

= 8 microns (0.008 mm, 0.000315 in)

Therefore, it is obvious that control of the quality of the

Human Hair

= 70 microns (0.07 mm, 0.00275 in)

hydraulic fluid helps prevent hydraulic equipment problems

Grain of Salt

= 100 microns (0.1 mm, 0.00394 in)

and greatly improves safety and reliability. Furthermore from

an economic angle it extends the life of the hydraulic fluid if

Smallest particle visible to the naked eye is 40 microns

quality is maintained.

(0.00157) approximately.

Effects of Contamination

Standards will often be quoted to ISO (International

Standards Organisation) for which literature can be

obtained.

Once inside the system, hydraulic circuit contaminants

greatly effect the performance and life of hydraulic

equipment. For example, contaminants in a hydraulic pump

Filters

develop internal wear to cause internal leakage and hence

lower discharges. Wear particles generated will circulate

The filter assembly fitted to all product ranges is designed to

with the hydraulic fluid to cause further deterioration in the

filter all the contamination that is generated through use to

performance of this and other equipment.

the required level of cleanliness. The filter must be serviced

to the requirements of the machine Service Schedules.

Contaminants also enter principal sliding sections of the

equipment causing temporary malfunction, scuffing, sticking

To ensure optimum performance and reliability it is

and leakage and can lead to major problems.

important that the machines hydraulic system is serviced

periodicaly in accordance with the manufacturers

The main contaminants can be classified as follows:-

requirements. For service schedules refer to Section 3

Routine Maintenance.

1

Solid Particles - sand, fibres, metallic particles,

welding scale, sealing materials and wear particles etc.

2

Liquid - usually water and incompatible oils and

greases.

3

Gases - Air, sulphur dioxide etc. which can create

corrosive compounds if dissolved in the fluid.

These contaminants can appear during manufacture,

assembly and operation.

Cleaning Operation

The purpose of cleaning oil is to remove contaminants of all

types and sludge by filtering hydraulic fluid through a

cleaning unit, as illustrated or similar. General Bulletin 011

also refers.

Procedure

Connect the cleaning unit in place of the hydraulic filter and

run the system for sufficient time to pump all the hydraulic

fluid through the unit. Disconnect the cleaning unit and

reconnect the filter. Top up the system with clean hydraulic

fluid as required.

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Issue 1

Section E

Hydraulics

Section E

21 - 1

Service Procedures

21 - 1

A

B

D

A

B

C

A396190

A

9803/3280

Issue 1

Section E

Hydraulics

Section E

22 - 1

Service Procedures

22 - 1

Variable Flow Pumps

Flow and Pressure Testing

D

C

A

B

S315770

9803/3280

Issue 1

Section E

Hydraulics

Section E

22 - 2

Service Procedures

22 - 2

Variable Flow Pumps

Flow and Pressure Testing

Load Sensing Pressure

Stand-by Pressure

With no services operating, there should be no pressure in

With the engine switched off, the pump swashplate is spring

the load sense line, this is because hydraulic oil flows

loaded to the full flow position. On engine start up standby

through the load sense circuit back to the hydraulic tank. If a

pressure moves the swash plate to minimum flow position

shuttle valve is ‘stuck’, or a hose kinked, then a pressure

(see descriptions). To check stand-by pressure:

could be induced in the load sense lines, this will have an

effect on the hydraulic system. To check load sense

1

Warm the hydraulic oil to working temperature, i.e.

pressure:

50°C (122°F):

1

Warm the hydraulic oil to working temperature, i.e. 50°C

a Set the engine speed to 2200 rev/min.

(122°F):

b Operate the loader shovel dump service to blow off

a Set the engine speed to 2200 rev/min.

the auxiliary relief valve.

b Operate the loader shovel dump service to blow off

2

Lower the backhoe bucket and loader shovel to rest on

the auxiliary relief valve.

the ground; stop the engine; operate the control levers

to vent residual hydraulic pressure.

2

Lower the backhoe bucket and loader shovel to rest on

the ground; stop the engine; operate the control levers

3

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to vent residual hydraulic pressure.

to pressure test connector B located on the pump

pressure out line.

3

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to pressure test connector A located on the load sense

4

Start the engine and run at 2200 rev/min.

line from the loader valve.

5

Do not move the steering wheel and make sure that all

4

Start the engine and run at 2200 rev/min.

control levers remain in ‘neutral’ position.

5

Do not move the steering wheel and make sure that all

6

Check the pressure gauge reading, which should be as

control levers remain in ‘neutral’ position.

specified in Technical Data.

6

Check the pressure gauge reading, which should be as

7

If the pressure is not as specified, do not make any

specified in Technical Data.

adjustments at this stage. Complete the other checks

detailed in this section.

7

If the pressure is higher than specified, first move the

steering wheel and then any of the service levers. If this

8

Refer to Regulator Valve Adjustment.

does not reduce the pressure, physically check the load

sense lines for trapping or kinking. As a last resort, the

service valves may have to be removed and checked for

sticking shuttle valves. However, this should not be

done until all other checks have been completed.

8

Machines with the load sense pressure relief valve

adjust the load sense pressure relief valve E. Machines

without a load sense pressure relief valve adjust the

regulator valve.

E

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Issue 1

Section E

Hydraulics

Section E

22 - 3

Service Procedures

22 - 3

Variable Flow Pumps

Flow and Pressure Testing (Cont’d)

3

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

Maximum Hydraulic Stall

to pressure test connector B located on the pump

pressure out line.

With variable flow hydraulics the pump swashplate angle will

increase or decrease according to pressure demand.

4

Start the engine and run at 2200 rev/min.

However in situations of maximum hydraulic stall, i.e. ram full

travel, the pressure in the circuit will achieve the setting of

5

Raise the loader arms to achieve full travel, hold the

the pressure regulator spool. To check the setting:

arms in this position and note the gauge reading, which

should be as specified in Technical Data.

Note: Machines with a load sense relief valve, disconnect

and blank the load sense relief valve E at F.

6

If the pressure is higher than specified, the pressure

compensator spool may be set incorrectly or the

1

Warm the hydraulic oil to working temperature, i.e. 50°C

swashplate may not be moving.

(122°F):

If the pump pressure is lower than specified, the flow

a Set the engine speed to 2200 rev/min.

spool may be set incorrectly, or there may be a leak in

the load sense line.

b Operate the loader shovel dump service to blow off

the auxiliary relief valve.

Do not make any adjustments at this stage. Complete

the other checks detailed in this section.

2

Lower the backhoe bucket and loader shovel to rest on

the ground; stop the engine; operate the control levers

7

Refer to Regulator Valve Adjustment.

to vent residual hydraulic pressure.

D

C

B

E F

S315770

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Issue 1

Section E

Hydraulics

Section E

22 - 5

Service Procedures

22 - 5

Variable Flow Pumps

Regulator Valve Adjustment

Note: If a new regulator valve is fitted, or a valve stripped,

cleaned and rebuilt, then the pressure spool should be

backed off to a low pressure. This will prevent inadvertent

damage to the pump.

Flow Regulator Spool

Pressure Regulator Spool

The pressure in the pump out line (pressure test connector

As previously explained, there is no ‘main relief valve’ to

B) should be 20 bar (290 lbf/in²) greater than the pressure in

control the system pressure (the pump swashplate angle will

the load sense line (pressure test connector A). If not adjust

increase or decrease according to pressure demand).

the regulator flow spool as described below:

However in situations of maximum hydraulic stall, i.e. ram full

travel, the pressure in the circuit will achieve the setting of

1

Lower the backhoe bucket and loader shovel to rest on

the pressure regulator spool. To adjust the setting:

the ground; stop the engine; operate the control levers

to vent residual hydraulic pressure.

1

Lower the backhoe bucket and loader shovel to rest on

the ground; stop the engine; operate the control levers

2

Gain access to the regulator valve assembly (mounted

to vent residual hydraulic pressure.

on the pump).

2

Gain access to the regulator valve assembly (mounted

3

Remove cap C and loosen locknut D.

on the pump).

4

Turn adjusting screw E clockwise to increase pressure

3

Remove cap F and loosen locknut G.

setting and anti-clockwise to decrease setting.

4

Turn adjusting screw H clockwise to increase pressure

5

Repeat pressure test as detailed previously and

setting and anti-clockwise to decrease setting.

establish valve is set correctly.

5

Repeat pressure test as detailed previously and

6

Tighten locknut, refit cap.

establish valve is set correctly.

6

Tighten locknut, refit cap.

F

C

G

D

H

E

A

B

S273401

S273100

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Issue 1

Section E

Hydraulics

Section E

22 - 6

Service Procedures

22 - 6

Variable Flow Pumps

Regulator Valve Adjustment (Cont’d)

The load sense system is a dynamic type, which means a

small flow (0.22 to 1.1 gall/1 to 5 litre per minute) is

circulated through the load sense line.

The flow is available due to a 0.02 in (0.6 mm) orifice in the

flow regulator spool in the pump control housing. This orifice

can be blocked or partially restricted which will give poor

performance, slow operating speed and/or low maximum

stall speed. If completely blocked, margin pressure and

stand-by pressure can be difficult to adjust and the loader

services may operate intermittently even though the

excavator operates correctly.

If any of the above symptoms are experienced carry out the

following:

1

Lower the backhoe bucket and loader shovel to rest

on the ground. Stop the engine and remove the

starter key.

2

Gain access to the regulator valve assembly.

3

Disconnect the load sense line at A. Attach a 0.25

inch (6.35 mm) hose to pump of suitable length to

route to a measuring container.

4

Start the engine and measure the flow which should

be at least 0.22 gall/1 litre per minute at 2200 RPM.

5

If the flow is below 0.22gall/1 litre per minute, remove

spool B and clean/unblock orifice C as required.

6

Fit spool B and check the flow as described at step 3

and 4.

7

If the flow is within limits check the stand-by pressure.

Refer to Flow and Pressure Testing.

B

B

C

A

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Issue 1

Section E

Hydraulics

Section E

22 - 7

Service Procedures

22 - 7

Variable Flow Pumps

Renewing Drive Shaft Seal

Note: The following procedure describes renewal of the

shaft seal. However this is not the normal sequence, the

sealing ring would normally be assembled with the taper

roller bearing from inside the pump to ensure a secure

sealing condition. If the shaft seal is to be renewed in this

manner, it is extremely important not to scratch or damage

the shaft, otherwise leakage will occur.

1

Remove retaining ring 1 and use a special rounded tool

such as a ground screwdriver to remove the drive shaft

sealing ring 2.

2

Examine the seal running area (driveshaft and housing)

for wear or damage. Damage in these areas will require

the pump to be further dismantled.

3

Lubricate the new seal with JCB Special MPL Moly

Grease.

4

Install the new seal, it is advisable to use a tube or

similar located over the driveshaft to ensure the seal

enters the housing evenly. DO NOT push the seal too

far into the housing. If the shaft seal touches the

bearing, the seal will be damaged.

5

Assemble the retaining ring 1.

2

1

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Issue 1

Section E

Hydraulics

Section E

23 - 1

Service Procedures

23 - 1

Loader Valve - Pressure Testing

Main Relief Valve (M.R.V.)

Make sure that the hydraulic oil is at working temperature,

i.e. 50°C (122°F).

Lower the backhoe bucket and loader shovel to rest on the

ground; stop the engine; operate the control levers to vent

residual hydraulic pressure.

1

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to pressure test connector A on the loader valve, (refer

to Service Tools).

2

With the engine running at 1500 revs/min, check M.R.V.

pressure by raising or lowering the loader arms until the

rams are fully open or closed and noting the maximum

gauge reading. CAUTION: Do not select 'float'. The

maximum pressure should be as stated in Technical

Data.

Note: The rams must be 'held' open or closed when reading

gauge.

A

3

If the pressure is incorrect, loosen locknut D and adjust

screw C. Turn it clockwise to increase pressure and

anti-clockwise to decrease the pressure. When the

pressure is correct, tighten the locknut and check the

352710

pressure again. Adjust as required.

C

D

A

S266281

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Issue 1

Section E

Hydraulics

Section E

23 - 2

Service Procedures

23 - 2

Loader Valve - Pressure Testing

Unloader Valve

Make sure that the hydraulic oil is at working temperature,

i.e. 50°C (122°F).

Lower the backhoe bucket and loader shovel to rest on the

ground; stop the engine; operate the control levers to vent

residual hydraulic pressure.

Make sure that the ‘hydraulic speed control’ and ‘smooth

ride system’ facilities are NOT switched on, otherwise the

correct unloader valve pressure cannot be obtained.

If the machine has a front-mounted roadbreaker, ensure that

the roadbreaker control valve lever is in the 'off' position

(lever down), otherwise the roadbreaker relief valve will

operate and prevent unloader valve pressure from being

reached.

1

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to pressure test connector A.

2

With the engine running at 1500 revs/min, slowly

operate arms raise or lower.

Note 1: The arms raise or lower service is specified because

it has no auxiliary relief valve (A.R.V.). Selecting this service

ensures that the pressure vents through the M.R.V. and not

an A.R.V.

3

When the service reaches full travel, return the lever to

the neutral position. Select the service again, very

slowly, the pressure gauge will rise until a step/kick is

A

352710

seen in the rate of change in the pressure increase. This

is the start of unloader operation. Keep selecting the

service until a sudden sharp increase in pressure is

observed with a change of engine sound, this point is

the unloader setting and should be as specified in

Technical Data.

4

If the pressure is incorrect, slacken locknut E and

adjust cap F. Turn it clockwise to increase pressure and

anti-clockwise to decrease the pressure. When the

pressure is correct, tighten the locknut and check the

F

pressure again. Adjust as required.

If the correct pressure cannot be achieved, add or

E

subtract shims as required, refer to Loader Valve -

Fixed Flow, Dismantling and Assembly - Unloader

Valve.

A

S266300

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Issue 1

Section E

Hydraulics

Section E

23 - 3

Service Procedures

23 - 3

Loader Valve - Pressure Testing

Hydraulic Speed Control (HSC)

The following procedure can be used to establish if the

hydraulic speed control facility is working correctly.

Make sure that the hydraulic oil is at working temperature,

i.e. 50°C (122°F).

Lower the backhoe bucket and loader shovel to rest on the

ground; stop the engine; operate the control levers to vent

residual hydraulic pressure.

1

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to pressure test connector A.

2

With the engine running at 1500 revs/min, slowly

operate arms raise, the pressure should be

approximately 138 bar (2000 lbf/in²).

3

Make sure that the HSC rocker switch (mounted on the

console) is in the OFF position. Raise the arms slowly,

select the rocker switch to ON, the arms should raise

quicker.

4

Make sure that the HSC rocker switch (mounted on the

console) is in the OFF position. Raise the arms slowly,

A

352710

press the button on the loader control knob, the arms

should raise quicker.

5

If the loader arms fail to respond, then check the HSC

hydraulic and electrical circuits for any faults.

9803/3280

Issue 1

Section E

Hydraulics

Section E

23 - 5

Service Procedures

23 - 5

Loader Valve - Pressure Testing

Auxiliary Relief Valves - Using Hand Pump

6

7

To pressure test and re-set the auxiliary relief valves

4

2

(A.R.V.'s), service kit 892/00309 must be used.

The service kit comprises; a test block 1, a setting body 2

1

with adjusting pin 3, a special spanner 4, anti-cavitation lock

out bung 5. A.R.V. cartridge removal tool 892/00335

comprises; an extractor cap 6 and a 'C' washer 7.

3

5

S196700

1

Remove the complete A.R.V. assembly from the valve

block. If the A.R.V. sub-assembly 7 remains in the valve

E

block, proceed as follows:

!

@

a

Fit extractor cap 11 over the A.R.V. sub-assembly

7

7, into the valve block E.

b

Fit 'C' washer 12 on top of the extractor cap, but

under the anti-cavitation spring seat as shown.

c

Unscrew the extractor cap, - the A.R.V. sub-

assembly will withdraw with the extractor cap.

S162560

2

Use special spanner 4 located in cross holes A and

separate the A.R.V. sub-assembly 7 from its cap 8.

A

4

8

S162570B

7

3

Install adjusting pin 3 into setting body 2.

2

3

S162570C

9803/3280

Issue 1

Section E

Hydraulics

Section E

23 - 6

Service Procedures

23 - 6

Auxiliary Relief Valves - Using Hand Pump

4

Install the A.R.V. sub-assembly into setting body 2.

Make sure that the adjusting pin 3 correctly locates in

adjusting screw 9.

Make sure that the lock nut 10 correctly locates in the

3

setting body socket - the anti-cavitation cone should

0

still be closed, as shown at B.

9

2

B

S162570D

5

Install the A.R.V. sub-assembly and setting body into

test block 1. Make sure that the assembly is installed in

the port marked 'RV' (relief valve).

1

S162570E

6

Connect a hydraulic hand pump to port 'P' (pump) of

S162570F

the test block 1. Make sure that the hand pump is filled

with JCB Hydraulic fluid.

Connect a 0 to 400 bar (0 to 6000 lbf/in²) pressure test

1

gauge to port 'G' (gauge) of the test block 1.

Port 'T' (tank) can be left open when using a hydraulic

hand pump.

7

Raise the pressure at the valve inlet using the hydraulic

hand pump, when the A.R.V. 'cracks' and oil escapes

S162570F

from the port marked 'T' the pressure gauge will

indicate the A.R.V. setting.

If the A.R.V. setting is correct, move to step 12.

If the A.R.V. setting is not correct, move to step 8.

9803/3280

Issue 1

Section E

Hydraulics

Section E

23 - 7

Service Procedures

23 - 7

Auxiliary Relief Valves - Using Hand Pump

8

Use the hand pump to raise approximately 172 bar

(2500 lbf/in²) pressure at the valve inlet.

Note: Raising the pressure at the valve inlet locks the anti-

cavitation cone C onto its seat, this allows the A.R.V.

adjusting screw lock nut 10 to be loosened (step 10).

0

C

If the pressure is maintained move to step 10.

If the pressure falls off rapidly, or if no pressure can be

obtained it is possible that the anti-cavitation cone is

not seating effectively, in this instance move to step 9.

S162570G

9

If no pressure can be raised (see step 8) at the valve

inlet, remove the A.R.V. assembly and install anti-

cavitation lock-out bung 6 in the port marked 'RV',

make sure that the bung O-ring face seal D is facing

D

out. Re-fit the A.R.V. assembly.

Note: The anti-cavitation lock-out bung seals and locks the

A.R.V. anti-cavitation function. The bung is only suitable for

the test block application and must NEVER be fitted to the

valve block.

6

The bung can be extracted using a 3/8 - 16 UNC

threaded bolt.

S162570H

10

Release the A.R.V. adjusting screw lock nut (see note):

Engage the nut at the end of setting body 2 using the

4

slot in special spanner 4, turn the nut anti-clockwise to

release the A.R.V. adjusting screw lock nut.

Note: Remember, it will not be possible to release the lock

nut if there is not approximately 172 bar (2500 lbf/in²)

pressure at the valve inlet.

2

S162570J

11

Insert an allen key into adjusting pin 3 (T-Bar type

shown). Push the adjusting pin down and make sure it

has engaged with the A.R.V. adjusting screw.

4

Rotate the T-bar clockwise to increase the pressure

setting and anti-clockwise to decrease the pressure

setting.

3

After adjustment, use the slot in spanner 4 to lock the

A.R.V. adjusting screw lock nut (see note).

Note: Remember, pressure must be maintained at the valve

inlet to ensure the lock nut is tightened.

S162570K

9803/3280

Issue 1

Section E

Hydraulics

Section E

23 - 9

Service Procedures

23 - 9

Excavator Valve - Pressure Testing

Auxiliary Relief Valves - Using Hand Pump

The auxiliary relief valves found in the backhoe valve block

are identical in design to those found in the loader valve

6

7

4

block.

2

Therefore please refer to Loader Valve - Pressure Testing,

1

Auxiliary Relief Valves (ARV’s) for the correct pressure test

procedures.

To pressure test and re-set the auxiliary relief valves

(A.R.V.'s), service kit 892/00309 must be used.

The service kit comprises; a test block 1, a setting body 2

3

with adjusting pin 3, a special spanner 4, anti-cavitation lock

out bung 5. A.R.V. cartridge removal tool 892/00335

5

S196700

comprises; an extractor cap 6 and a 'C' washer 7.

9803/3280

Issue 1

Section E

Hydraulics

Section E

23 - 10

Service Procedures

23 - 10

Excavator Valve - Precision Control (Servo)

(Machines up to serial no. 931159)

*

Pressure Testing

Load Sense Drain Regulator and Relief Valve

Make sure that the hydraulic oil is at working temperature,

i.e. 50°C (122°F).

Lower the backhoe bucket and loader shovel to rest on the

ground; stop the engine; operate the control levers to vent

residual hydraulic pressure.

1

Connect a 0 - 400 bar (0 - 6000 lbf/in²) pressure gauge

to pressure test connector A on the loader valve, (refer

to Service Tools).

2

With the engine running at 1500 revs/min, check that

the M.R.V. pressure is correct, see Loader Valve -

Pressure Testing, Main Relief Valve.

3

With the engine running at 1500 revs/min, operate a

stabiliser service fully and at the same time note the

A

reading in the gauge which should be as stated in

Technical Data.

Note: The ram must be 'held' open or closed when reading

gauge.

4

If the pressure is incorrect, loosen locknut D and adjust

screw C. Turn the screw C clockwise to increase

pressure and anti-clockwise to decrease the pressure.

When the pressure is correct, tighten the locknut and

check the pressure again. Adjust as required.

C

D

A402500

9803/3280

Issue 2*

Section E

Hydraulics

Section E

24 - 1

Service Procedures

24 - 1

Ram Creep Tests - All Services

If ram creep is suspected the following procedures must be

3

Operate the rams to ensure they are full of hot oil.

carried out to define if the leakage is within tolerance. Ram

creep can be caused by a number of reasons:

4

Apply a load to the suspect ram for example the boom

Cylinder/Piston Leakage, Spool Leakage, ARV Leakage.

ram by raising the dipper to the horizontal as at B.

The text and illustrations show a typical ram installation (in

5

Measure the actual piston rod movement over 10

this instance the boom ram), the principle applies to all

minutes. Measure the movement by checking the pivot

rams.

pin to pivot pin dimensions as at C. Alternatively mark

the rod with a felt tip pen 150mm (5.9 in) from the end

Note: The procedures are not applicable for rams fitted with

cap and check the movement after 10 minutes, this is

hose burst protection valves.

not possible on the majority of boom/extending dipper

rams.

! WARNING

Hydraulic fluid at system pressure can injure you. Before

6

Using Table 1, check if the piston rod movement is within

disconnecting or connecting hydraulic hoses, stop the

the recommended tolerance. If so, the ram creep is

engine and operate the controls to release pressure

acceptable.

trapped in the hoses. Make sure the engine cannot be

started while the hoses are open.

Note: The table indicates the MAXIMUM permitted ram

INT-3-1-11/1

movement.

! WARNING

7

If the rate of movement is unacceptable, identify if the

Take care when disconnecting hydraulic hoses and

fault is as a result of cylinder/piston leakage or spool

fittings as the oil will be HOT.

leakage at the control valve, see procedure B and C.

TRANS 1-2

A Test for Ram Creep

1

Operate the machine to bring the hydraulic oil to a

normal working temperature of 50°C (122°F) which can

be measured using a hydraulic oil temperature probe

(service tool 892/00285).

2

Fit an appropriate pressure gauge A to a tee-piece in the

service hose which is pressurised when the ram in

question is supported (Fig 1).

A

C

B

C

FIG 1

380190

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Issue 1

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