Dismantling and Assembly
Manual Control
The numerical sequence shown on the illustration is intended
as a guide to dismantling.
For assembly the sequence should be reversed.
Check Valves
Each of the identical load hold check valves
4R
to
4W
can
be removed as shown at
4W.
Make-up check valve
4X
is a
smaller size but otherwise identical.
Ensure good condition of seating faces on poppets
4
and
8
and on the mating faces in the valve block.
Spools
Spools
4A
,
4B
,
4E
and
4F
are identical but must not be
interchanged as they are matched to their bores. Stabiliser
spools
4C
and
4D
are identical to each other but different
from the excavator spools.
All spools have the same centring and sealing components
items
9
to
21
.
To completely dismantle a spool, follow the sequence
9
to
21
. To prevent spool rotation when turning screw
15
, hold a
rod through the eye end of the spool.
If only renewing the seals, dismantle as far as cap
14
then
remove items
15
to
22
as an assembly.
Lubricate new seals with JCB Hydraulic Fluid and take care
to prevent them from being damaged by the sharp edges of
the spool.
Apply JCB Threadlocker and Sealer to threads of screw
15
.
Relief Valves
A.R.V's
4H
to
4P
appear identical but have various pressure
settings, refer to
Technical Data
. Ensure that they are
correctly adjusted and fitted in their specified positions.
Relief valve dismantling and assembly procedures are
detailed separately.
Note:
All hydraulic adapters that are installed together with a
bonded sealing washer must also have JCB Threadseal
applied to the threads of the adapter.
Assembly
1
Fit the boot
10
to the seal plate
11
.
2
Fit a new lipseal
12A
into the valve block, ensure
square. Fit wiper
12
on top of lipseal.
3
Fit the seal plate and boot assembly to valve block but
do not torque tighten capscrews
9
at this stage. Ensure
wiper locates into seal plate.
4
Use clean hydraulic oil as a lubricant. From the bottom,
insert spool through the valve block, do not use
excessive force when fitting, a turning motion should
ease the spool through the valve block.
5
Check that the tang end of the spool passes through
the boot without dislodging or damaging the boot.
Ensure that the tang aligns with the control rod and
that the boot is not distorted and is located in the spool
land.
6
Torque tighten cap screws
9
.
7
When fitting bolt
15
, clean the threads thoroughly using
JCB Cleaner/Degreaser, leave it for 10 minutes then
apply a small quantity of JCB Threadlocker and Sealer
to the threads of the spool.
8
Make sure that all the parts move freely, check that
item
16
does not interfere with item
18
.
9
Renew 'O' ring
21
and seal
20
. Make sure the 'O' ring
and wiper seal are not trapped or damaged.
10
Fit seal
20
and seal plate
19
to the valve block section.
Torque tighten capscrew
13
on completion.
Re-connect the lever mechanism to the tang (lever) end of
the spool.
Run the engine and inspect the valve for external leaks.
Torque Settings
Item
Nm
kgf m
lbf ft
1
122
12.4
90
5
80
8.3
60
9
9.5 0.96 7
13
7
0.7
5
15
11
1.1
8
23
95
10
70
61 - 2
Section E
9803/3280
Section E
61 - 2
Issue 1
Excavator Valve