JLG sky trak mmv Service Manual page 416

Hydraulic System
b. Secondary Function Manifold Disassembly,
Cleaning, Inspection and Assembly
1. Secure the secondary function manifold (1) in a
suitable bench vise if possible.
6
5
4
2. Remove the 550 psi (38 bar) pressure-reducing
valve (2).
3. Remove the 650 psi (45 bar) pressure-relief
valve (3).
4. Remove the solenoid nuts (4), coils (5) and
cartridges (6).
5. Remove the check valve (7).
6. Clean all components with a suitable cleaner before
inspection.
7. Inspect the solenoid cartridges for proper operation.
Check by shifting the spool to ensure that it is
functioning properly. Check that the spring is intact.
Inspect the cartridge interior for contamination.
9.118
2
3
1
7
6
5
4
MM4200
8. Inspect internal passageways of the secondary
function manifold and its component parts for wear,
damage, etc. If inner surfaces of the secondary
function manifold DO NOT display an ultra-smooth,
polished finish, or components are damaged in any
way, replace the secondary function manifold or
appropriate part. Often, dirty hydraulic fluid causes
failure of internal seals and damage to the polished
surfaces within the secondary function manifold.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and opera-
tion. Lubricate seals and o-rings with clean hydraulic oil.
9. Secure the secondary function manifold (1) in a
bench vise or by other suitable means.
10. Install the pressure reducing valve assembly (2) and
torque to 35-40 lb/ft (47-54 Nm).
11. Install the relief valve assembly (3) and torque to
25-30 lb/ft (34-41 Nm).
12. Install the check valve (7) and torque to 25-30 lb/ft
(34-41 Nm).
13. Install the solenoid cartridges (6) and torque to
25-30 lb/ft (34-41 Nm). Install the solenoid coils (5) and
nuts (4). Torque the nuts to 4-6 lb/ft (5-8 Nm).
c. Secondary Function Manifold Installation
1. Align the secondary function manifold with its mount
holes on the hydraulic reservoir/engine mount.
2. Align gaskets, bolt holes, etc., with component
mount holes. Secure the secondary function
manifold with the necessary fasteners. Torque
fasteners to specification. Refer to the fastener
torque chart in Section 2.3, Torques .
3. Before attaching the hoses, prime the secondary
function manifold by filling the hydraulic hose ports
with fresh, filtered hydraulic fluid from a clean
container.
4. Use new oiled o-rings as required. Reattach and
secure all diagnostic test nipples, hoses, clamps,
wiring, etc.
5. Check the routing of all hoses, wiring and tubing for
sharp bends or interference with any rotating
members, and install tie wraps and/or protective
conduit as required. Tighten all tube and hose
clamps.
Model MMV Rev. 12/04