The factory tear-down for your JCB JS70 runs 385 pages and carries OEM #9803/6020, covering the hydraulic pump, traction motor, and engine control system end to end. Hydraulic schematics walk through pressure testing and cushion valve function, while the electrical layouts trace every wire back to its connector. The troubleshooting section runs deep, taking you through faults in the traction gearbox, recoil unit, and main control valve one step at a time on genuine factory logic. Torque the travel motor mounting hardware to 268-312 Nm (197-230 lbf ft), then work the hydraulic air bleeding procedure straight through. No more tearing into the undercarriage on a hunch. The file is fully bookmarked, so load it on a tablet, jump to the spec you need, and get the machine tracking straight again.
What's Inside This JCB JS70, Isuzu 4JB1 PAA-04 Manual
| System | Pages | Key Topics |
|---|---|---|
| Care & Safety | 14-19 | Safety Notices, General Safety, Operating Safety, Maintenance Safety |
| Body & Framework | 57-59 | Weights |
| Electrics | 60-93 | Torque Specifications, Technical Data, Battery Testing, Schematic Diagram, Layout, Engine Control |
| Schematics | 96-133 | Technical Data |
| Pressure Testing | 134-147 | - |
| Hydraulic Pump | 148-164 | Function Chart |
| Control Valve | 165-200 | - |
| Remote Control Valve Hand | 201-215 | - |
| Hydraulic Rams | 216-259 | Multiple Valves, Cushion Valves |
| Rotary Coupling | 260-269 | - |
| Slew Motor | 270-287 | - |
| Transmission | 288-348 | Traction Motor/Reduction Gear, Traction Gearbox |
| Track and Running Gear | 349-383 | Removal and Replacement, Idler Wheel and Recoil Unit, Idler Wheel, Recoil Unit, Grease Cylinder, Drive Sprocket, Top Roller, Bottom Roller |
| Engine | 384-385 | Technical Data |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Hydraulic System Air Bleeding Procedure | Refer to procedure | p. 33 |
| General Torque Settings Procedure | Refer to tables | p. 4 |
| Travel Motor Mounting Torque | 268~312 Nm (197~230 lbf ft) | p. 4 |
| Hydraulic System Fault Diagnosis Procedure | Refer to fault finding sections | p. 163 |
| Track Gearbox Oil Service Procedure | Refer to procedure | p. 42 |
| Hydraulic Pump Displacement Volume | 36 cm3/rev x 2 (2.196 in3/rev x 2) | p. 96 |
| Hydraulic Pump Working Pressure | 284.4 bar (4125 lbf/in2) | p. 96 |
| Hydraulic Return Filter Replacement Interval (100% breaker use) | Every 100 hrs | p. 24 |
| Hydraulic Suction Filter Cleaning Interval (100% breaker use) | Every 100 hrs | p. 24 |
| Fuel Hose (fuel tank - engine) Replacement Interval | Every 4000 Operating Hours or 2 Years | p. 27 |
| Fuel Hose (fuel filter - injection pump) Replacement Interval | Every 4000 Operating Hours or 2 Years | p. 27 |
| General O-rings, Seals and Gaskets Replacement | Renew whenever disturbed unless otherwise instructed | p. 19 |
JCB JS70, Isuzu 4JB1 PAA-04 Common Problems This Manual Covers
Hydraulic functions turn slow and erratic while the pump puts out a loud grinding noise p. 163
Test the hydraulic pump working pressure first and confirm it reaches 284.4 bar (4125 lbf/in2) per page 96. Drain the 92 litres (20.26 UK gal) of fluid before you pull the pump housing. With the internals exposed, fit fresh O-rings and gaskets on every joint you break.
Manual Section: Hydraulic Pump Fault FindingBoom and arm drop under heavy loads while hydraulic oil leaks visibly from the main control block p. 184
Inspect the main control valve assembly against the guidelines on page 184. If the spool is bent, swap the whole valve assembly rather than chasing it. Torque the main relief valve cap 1 to 49-54 Nm (36-40 lbf ft) per page 199, and replace its seals as you go.
Manual Section: Control Valve Fault FindingMachine tracks bind during forward operation and a loud popping noise comes from the traction gearbox assembly p. 325
Measure the track gearbox spindle 2 reamer hole bore diameter against the figures on page 325. Replace the spindle once the bore passes its maximum limit of ø 19.056 mm (0.750 in). Drain the housing and check the internal gears for metal debris before you reassemble.
Manual Section: Traction Gearbox Inspection and Corrective ActionEngine fails to crank in cold weather and the starter solenoid only emits a rapid clicking sound p. 60
Check the battery charge and go over every terminal connection. Torque the battery securing bolts to 19.6-29.4 Nm (14.46-21.69 lbf ft) per page 61. Scrub the posts with a wire brush so corrosion stops choking the voltage headed for the starter.
Manual Section: ElectricsFrequently Asked Questions
How do I reset the hydraulics on a JCB JS70?
Start by releasing the tank pressure: remove the cap and press the projection until the pressure is gone (page 33). After you replace hydraulic oil or any component, bleed air from the circuit, the pump, rams, and slew motor included, following the "Air Bleeding Procedures" (page 33-35). At the pump, loosen plug A, prime with oil if needed, then idle the engine low and loosen plug A again until oil weeps out (page 34).
How do I diagnose a JCB JS70 solenoid problem?
Work from the "Multiple Valve - Fault Finding" table on page 220. Symptoms like "Does not return to neutral" on Shut off Valve 1 or 2, or "No inlet pressure" at the Shuttle Valve, point to a "Malfunction of the solenoid valve 2" or "Malfunction of the solenoid coil 20". The listed countermeasures are replacing the spring or coil, or dismantling and cleaning the valve.
What should I check if a JCB JS70 has no hydraulic response?
When the hydraulic system runs poorly or quits entirely, check for pump problems, foreign matter clogging the relief valve, or relief valve trouble (page 185). Look next at ram trouble, a heavy load, cracks in the valve, or a spool that does not stroke fully. Confirm the oil level is not too low, then check for clogged filters or kinked hoses (page 185).
How do I troubleshoot a JCB JS70 track motor issue?
Consult the "Traction Motor/Reduction Gear - Fault finding" table on page 294. With no oil pressure present, a motor that will not start points to low relief valve pressure, pump failure, or direction switching valve failure. With oil pressure present, look at brake valve failure, hydraulic motor failure, broken gear teeth, or overloading (page 294).
What format is this manual in?
It downloads instantly as a PDF. The full 385-page searchable Service Manual lands the moment payment clears, ready to open on a laptop, tablet, or phone right in the shop.
Are there any print restrictions on this manual?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
Are there wiring harness diagrams in this JCB JS70, Isuzu 4JB1 PAA-04 manual?
Included. The JCB JS70, Isuzu 4JB1 PAA-04 Service Manual covers complete wiring harness diagrams, electrical circuits, and connector pinouts.
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