1990–1997 Liebherr R 900–942 Litronic Hydraulic Excavator Service Manual (P/N 8502675)

This 1990–1997 Liebherr R 900–942 Litronic service manual, publication ID 8502675, is the July 1997 issue incorporating supplements through No. 05–07/97. It also covers shared components used on the listed A-series excavators.

• Hydraulic diagnosis: Model-specific pressure checks, LPVD double-pump regulation, primary and secondary relief-valve adjustment, leak-off testing, and hydraulic-cylinder removal and resealing.

• Litronic electrical controls: GLR and GLD horsepower-control tests, engine-speed sensor checks, low-idle troubleshooting, swing-brake diagnosis, and subsystem wiring diagrams.

• Swing and travel repair: SAT swing-gear service, Trasmital and FAT travel-gear resealing, brake-disc replacement, swing-ring installation, and track-component wear assessment.

• Engine and pump drive: Deutz and Liebherr diesel specifications, engine-speed adjustment, sensor-controlled low idle, coupling replacement, and PVG splitterbox disassembly.

• Special attachments: Load-holding valve adjustment, AS/ASH/AHS hydraulic installation kits, attachment-flow reduction, centralized lubrication, adjustable cabs, and quick-change coupler circuits.

• Cab climate systems: D1LC heater repair, D5W supplementary-heater testing and troubleshooting, and KONVEKTA air-conditioning service with refrigerant-specific information.

Written for skilled mechanics already familiar with excavator repair, this manual assumes access to standard workshop equipment and the special tools identified in its procedures.

Model Coverage and Engine Specifications

Subgroup indexes and modification charts identify the applicable models and serial breaks. The A-series coverage concerns shared assemblies; separate steering, oscillating-axle stabilizer, and wheeled-machine brake chapters are absent, as are axle-overhaul and two-speed gearbox repair sections.

Engine data distinguish Deutz BF4L 913 and BF4M 1013 E configurations alongside Liebherr diesel variants. The engine chapter concentrates on specifications, speed adjustment, and low-idle controls; it does not provide a complete internal diesel-engine overhaul.

Maintenance schedules, lubricant charts, and Fleetguard DCA4 coolant guidance are included. Detailed routine maintenance is assigned to the separate Operation and Maintenance Manual.

Hydraulic Pumps, Valves, and Cylinders

The hydraulic sections pair pressure-setting tables with adjustment checklists and test-point locations. LPVD pump documentation covers installation, startup, regulation, pressure cut-off, and wear assessment through leakage measurement.

A4V swing-pump adjustment, FMF and FMV motor operation, pilot controls, and main control-valve troubleshooting extend the coverage beyond pressure tables. Separate repair instructions are required for FMV motor resealing and internal repair.

Hydraulic-cylinder procedures cover removal, seal replacement, guide rings, cushioning arrangements, and reassembly. The R 932/R 942 closed swing loop has its own filtering procedure using kit 9368172 because that oil does not pass through the machine’s return filter.

Electrical Troubleshooting and Circuit Coverage

GLR and GLD sections describe testing with device 6202698, including pump-solenoid circuits, inductive engine-speed pickup checks, and regulator behavior. Test/result/cause/remedy charts help distinguish excessive engine lug-down caused by an electrical control fault from a hydraulic problem.

The manual warns that operating or jump-starting with the battery disconnected from the alternator can damage the horsepower controller’s voltage-protection circuitry.

Illustrated references include LPVD pump section views, boom/stick/bucket hydraulic function diagrams, low-idle sensor-control schematics, swing-brake control circuits, and D1LC heater wiring. Electrical component views identify connectors and terminal locations.

Wiring scope: Basic-machine sections provide component legends and cross-references, while subsystem and special-attachment schematics cover individual circuits. Complete basic-machine wiring sheets are not included.

Couplings, Gears, and Undercarriage

Coupling instructions distinguish Centaflex and other torsional-vibration damper arrangements, with installation-position checks and PVG 350 B 381 splitterbox service. Twisting the Centaflex aluminum segments during fastening can loosen the screws and destroy the coupling.

Travel-gear coverage separates Trasmital units from FAT versions with different bearing arrangements. Repair procedures address gear removal, resealing, travel-brake discs, and slipring seals.

Swing-ring work includes clearance checks, removal, mounting orientation, and installation. Track sections cover chain and pad replacement, idlers, tension units, track rollers, carrier rollers, and wear-limit charts.

Attachment Hydraulics and Cab Systems

AS, ASH, and AHS kits are organized by attachment function, with hydraulic schematics and pressure-adjustment guidance for grapple, cylinder, and hammer installations. Further sections address load-holding valves, pressure cut-in functions, centralized lubrication, movable cabs, and quick-change couplers.

D1LC heater coverage includes removal and component repair. D5W material adds fuel-delivery testing and troubleshooting charts; KONVEKTA air-conditioning coverage distinguishes R12 and R134a configurations.

Workshop Specifications and Tools

Reference material includes conversion factors, metric bolt-grade torque tables, UNC/UNF tightening values, ISO bore and shaft tolerances, fluid capacities, and electrical test specifications. Repair-welding guidance identifies structural-steel and electrode requirements.

Tool documentation covers electrical-connector service, injection-valve extraction, brake-housing fixtures, and the Litronic Measure System (LMS), including measurement inputs and calibration controls.

Observe the manual’s pressure-relief, attachment-support, and mechanical-locking precautions before maintenance or repair.

PDF Layout and Navigation

The printable 1,343-page PDF combines both service-manual volumes: opening index, 1 page; groups 1–8, 835 pages; groups 9–12 and 16–19, 507 pages. These counts include introductory material, revision charts, and 173 otherwise blank pages. PDF text search and embedded bookmarks are unavailable; small diagram labels require zooming, and some details are faint or crossed by a vertical print stamp.