This JCB 506C, 508C Service Manual (OEM #9803/3640U-8) runs 717 pages with one job: returning your 2005–2008 Loadall to factory spec, whether you run a 506C, 506CHL, or 508C. Full circuit schematics cover both Syncro Shuttle and Powershift transmissions, and the hydraulic schematic symbols carry model-split technical data separating 506C from 506CHL/508C machines. The wiring section traces every harness, fuse, relay, and alternator circuit. Torque tables run from Grade 12.9 fasteners at 80.0 Nm down to the 1/4-inch BSP hose fitting at 24.0–27.0 Nm, with ram end cap torque hitting 678 Nm. Tighten that hydraulic ram end cap to spec, not to what felt right last time. Everything is bookmarked by system and searchable by keyword, so you can pull it up on a tablet at the machine and find the exact number before the first wrench turns.
What's Inside This JCB 506C, 506CHL, 508C Manual
| System | Pages | Key Topics |
|---|---|---|
| Care and Safety | 40-57 | Safety Notices (Important Information, Operator Manual, Safety Warnings), Safety Check List (Safety - Yours and Others, Operating Safety, Maintenance Safety) |
| Attachments | 150-157 | Quick Release Couplings, Venting Hydraulic Pressure (Connecting and Disconnecting, Quick Release Couplings - Do's and Don'ts), Connecting Quick Release Couplings |
| Body and Framework | 158-191 | Service Procedures (Rivet Nuts, Slide Hammer Kit), Boom (Removal and Replacement, Shimming), Boom Chains (Servicing, Removal, Inspection and Replacement) |
| Electrics | 192-351 | Technical Data (Fuses and Relays), Basic System Operation (Circuit Schematics) |
| Controls | 352-359 | Dual Control Function Levers, Adjustment (Assembly), Fig 1, Fig 2, Fig 3, Fig 4 |
| Hydraulics | 360-459 | Technical Data (506C Machines, 506CHL and 508C Machines), Basic System Operation (Introduction to Hydraulic Schematic Symbols) |
| Transmissions | 460-641 | Technical Data (Syncro Shuttle, Powershift, Axles, Tyres, Recovery Procedure, Drive Paths), Fault Finding (Syncro Shuttle, Powershift) |
| Brakes | 642-671 | Technical Data (All Models), Basic Operation, Service Procedures (Brake Piston Seal Leakage, Introduction, Testing, Bleeding Procedure, Front Axle, Rear Axle) |
| Steering | 672-709 | Technical Data (506C, 506Chl & 508C), Basic System Operation (Hydraulic Steer Circuit) |
| Engine | 710-717 | Technical Data |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Metric Grade 12.9 Fasteners (M10, Condition 1) | 80.0 Nm | p. 15 |
| Drive shaft oil seal protrusion (if dimension V is 16 to 16.30 mm) | 2 mm | p. 635 |
| JCB Multi-Gasket quantity | 50 ml | p. 37 |
| BSP Hose (1/4 inch) torque setting | 24.0 - 27.0 Nm | p. 18 |
| Ram end cap (51-8) torque | 678 Nm | p. 454 |
| UNF Grade 'S' Fasteners (Condition 1) - 1/4 inch bolt torque | 11.2 Nm | p. 14 |
| UNF Grade 'S' Fasteners (Condition 1) - 1 inch bolt torque | 814.0 Nm | p. 14 |
| Metric Grade 8.8 Fasteners (Condition 1) - M5 bolt torque | 5.8 Nm | p. 14 |
| Metric Grade 8.8 Fasteners (Condition 1) - M36 bolt torque | 2399.0 Nm | p. 14 |
| Hydraulic BSP Adaptors Torque - 1/4 inch | 18.0 Nm | p. 17 |
| Hydraulic BSP Adaptors Torque - 1 1/4 inch | 206.0 Nm | p. 17 |
| Engine Oil Capacity | 10 liters | p. 80 |
JCB 506C, 506CHL, 508C Common Problems This Manual Covers
JCB 506C hydraulic boom jerks under load, loses power, or won't lift to rated height
Check hydraulic oil level; the 506C tank holds 121 liters (page 81). Inspect and replace the hydraulic filter element before chasing pressure faults. Verify main relief valve pressure reads 238 bar (page 77); anything lower points to a worn pump or stuck valve. Work through the fault-finding chart to isolate leaking seals or a failing cylinder.
Manual Section: HydraulicsBoom-end auxiliary hydraulics dead or attachment won't engage after connecting quick-release couplers p. 150
Vent residual hydraulic pressure before disconnecting; follow the quick-release coupling procedure on page 150 to avoid trapped pressure locking the coupler. Inspect coupling faces and seals for damage or contamination. Reconnect with engine at idle and cycle the auxiliary lever to purge air. Torque any disturbed BSP hose connections to 24.0-27.0 Nm for 1/4 inch fittings (page 18).
Manual Section: AttachmentsFreshly torqued bolts or repaired components back out, loosen, or fail again within hours p. 14
Verify every replacement bolt matches the original grade: JCB uses high-tensile fasteners and a lower-grade substitute will fail under working load. Check torque values on page 14; Metric Grade 12.9 M10 bolts require 80.0 Nm (page 15). Never reuse a fastener showing thread damage or stretch. Order genuine JCB hardware if grade is uncertain.
Manual Section: Care and SafetyPersistent oil weeping from driveline hub seals or hydraulic component joints after service p. 635
Clean the area and pinpoint the exact leak source before ordering parts. Drive shaft oil seals must sit 2 mm proud of the housing face during installation (page 635). Replace every seal and gasket disturbed during the repair: JCB service procedure requires full renewal, not reuse. Torque 1/4 inch BSP hydraulic adaptor fittings to 18.0 Nm (page 17) after reassembly.
Manual Section: TransmissionsBrakes feel spongy, pull to one side, or park brake won't hold on a slope p. 642
Bleed the brake circuit using the front and rear axle procedure in the Brakes section (page 642). Then test for brake piston seal leakage; the section covers both high- and low-pressure seal tests, where a failing seal shows a consistent pressure drop. Torque any disturbed BSP hydraulic connections to 18.0 Nm for 1/4 inch fittings (page 17) before re-testing.
Manual Section: BrakesSteering feels heavy, wanders off-line, or loses assist completely in one direction p. 672
Purge trapped air from the steering circuit first: it mimics a failing steer unit. Follow the 2-wheel or 4-wheel steer bleed procedure in the Steering section (page 672). Inspect all BSP adaptor connections and torque 1/4 inch fittings to 18.0 Nm (page 17). If bleeding doesn't restore full assist, tear down the steer unit per the dismantling procedure in the same section.
Manual Section: SteeringFrequently Asked Questions
What is the hydraulic pressure setting for a JCB 506C/506CHL/508C?
For 506C machines, the Main Relief Valve (MRV) setting is 238 bar (3500 lbf/in2) and the Filter Relief Valve Setting is 1.05 bar. For 506CHL and 508C machines, the MRV is also 238 bar (3500 lbf/in2), but the Filter Relief Valve Setting is 2 bar. The Load Sense (LS) Relief Valve Pressure for the steer unit is 175 bar (2538 lbf/in2) for earlier 506C models and 190 bar (2576 lbf/in2) for 506CHL/508C machines from SN 1184000.
What are the torque specs for JCB 506C/506CHL/508C wheel nuts or engine fasteners?
The torque setting for wheel nuts on all models is 680 Nm (500 lbf ft). For engine fasteners, specific torque settings vary depending on the component and fastener grade. For example, the engine oil drain plug should be tightened to 25 lbf ft (34 Nm) for A and R Series engines, while alternator mounting bolts for JCB 444 engines are 47 Nm (34.7 lbf ft). General torque tables for various fastener grades are provided in the manual.
What are the replacement specifications for oil seals?
For drive shaft oil seals, specific installation dimensions are provided. If dimension V (from shoulder W to circlip Z) is 16 to 16.30 mm (0.63 to 0.64 in), fit the new seal protruding by 2 mm (0.080 in). If dimension V is 17.3 to 17.5 mm (0.68 to 0.69 in), fit the new seal flush with the end of the housing. Always pack grease between the lips of the new seal before fitting.
What are the replacement specifications for gaskets?
The manual generally instructs to renew or fit new gaskets and O-rings during assembly and maintenance procedures. For general gasket flanges, JCB Multi-Gasket (Part No. 4102/1212, 50 ml quantity) is recommended as a medium strength sealant. Specific dimensions for replacement gaskets themselves are not provided, as they are typically replaced with OEM parts.
What format is this manual in?
Immediate download of the complete 717-page searchable Service Manual. Access it on any device: a laptop at your desk or your phone in the field.
Can I print this manual?
The PDF is DRM-free, so print whatever sections you need for the shop floor. Standard letter or A4 paper works.
Are there wiring harness diagrams in this JCB 506C, 506CHL, 508C manual?
Yes, this JCB 506C, 506CHL, 508C Service Manual includes complete electrical wiring diagrams, wire routing, and connector pinouts.
Document Quality
This document is a scanned PDF with an OCR layer, allowing you to search and copy the full text. The text quality is consistently clear and easy to read throughout. All diagrams and illustrations are raster images, but they are well-rendered with readable labels, ensuring clarity for technical procedures. The pages are clean with no noticeable scan artifacts, stains, marks, or skewed content. There are several "Page left intentionally blank" filler pages present in the document.
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