1997–2002 Fiat-Hitachi EX135 Excavator Service & Repair Manual (P/N 604.06.827, 604.06.822, 604.06.837)

• 633-page, three-volume PDF set of Fiat-Hitachi factory manuals for the EX135 excavator: Technical Manual - Operational Principle, Form/Part No. 604.06.827 (116 pages); Technical Manual - Troubleshooting, Form/Part No. 604.06.822 (217 pages); and Workshop Manual - Excavator, Form/Part No. 604.06.837 (300 pages). All are English-language Edition XI publications dated 1997.
• Explains the Main Controller (MC), EC motor, sensors, switches, and proportional solenoid logic behind Normal Control, HP Mode, E Mode, Auto-Idle, Engine Learning, arm regeneration, travel motor swash-angle control, and the four work modes.
• Provides factory performance testing and hydraulic diagnosis for engine, travel, swing, front-attachment, pilot, main-pump, relief-valve, pump-flow, and motor leakage or drain conditions.
• Includes Dr.EX fault-code and live-data diagnosis, service-mode adjustments, sensor ranges, symptom-based troubleshooting, monitor-panel fault tracing, connector testing, fuse and relay checks, and harness inspection.
• Covers upperstructure repair of the cab, counterweight, main frame, pump device and regulator, control valve, swing device, pilot valves, shockless valve, solenoid valve unit, and pilot relief valve.
• Details undercarriage and front-attachment repair for the swing bearing, travel device and motor, center joint, track adjuster, front idler, upper and lower rollers, tracks, bucket teeth, and hydraulic cylinders.
• Supplies electrical and hydraulic circuit diagrams, component layouts, torque tables, maintenance standards, wear limits, test specifications, and part-numbered special tools. The separate Engine Workshop Manual, Form/Part No. 604.06.832, is referenced but not included.

Operational Principles and System Layout

The Operational Principle volume follows signals from the engine control dial, pressure sensors, travel and front-operation switches, work-mode switch, and learning switch into the MC, then traces its commands to the EC motor and SC/SI solenoid valves. It explains the changes in engine speed and hydraulic response in Normal, HP, E, Auto-Idle, General Purpose, Grading, Precision, and Attachment modes.

Fiat-Hitachi also specifies when Engine Learning is required after replacement of the engine, engine-control cable, EC motor, or MC. The routine records the full-speed and idle governor-stop positions used by the controller.

Hydraulic chapters explain pump displacement and regulator summation control, main and pilot circuits, neutral and combined operation, arm regeneration, boom and arm anti-drift functions, travel flow control, boom regeneration, and travel/boom-lower selection. Component sections cover the variable-displacement pump, regulator, swing motor and brake valve, control valve, pilot valves, travel motor and counterbalance valve, shockless valve, center joint, and track adjuster.

Representative references include the Engine Control System layout, neutral and combined-operation hydraulic circuits, the Main Pump P-Q Diagram, the control-valve hydraulic circuit, the full Electrical System Circuit Diagram, and the full Hydraulic System Circuit Diagram. These drawings connect test points and component names when a fault crosses the electronic and hydraulic sides of the machine.

Diagnostic and Workshop Repair Coverage

The Troubleshooting volume separates diagnosis into fault-code, symptom, monitor-panel, electrical-inspection, and harness-check paths. Dr.EX diagnostic analyzer P/N 75301336 reads stored MC faults and monitors pump pressures, EC angle, engine-control input, solenoid commands, switch states, selected modes, and Engine Learning status in real time. Service mode covers mode-specific and breaker/crusher engine-speed adjustments. Circuit-check lamp harnesses are identified as P/N 75301514, 75301515, 75301516, and 75301484.

Factory tests cover travel speed and mistrack, parking-brake holding, swing speed and drift, swing-bearing play, digging-function drift, cylinder cycle time, combined boom-raise/swing response, pilot and main-pump pressures, relief-valve operation, pump flow, and motor drainage. Standard tables, sensor ranges, electrical values, and the pump P-Q reference help separate a control fault from worn hydraulic hardware before repair begins.

The 300-page excavator workshop volume adds removal and installation procedures, exploded views, disassembly and reassembly coverage, maintenance standards, and special-tool callouts. The pump chapter warns that the right- and left-side valve plates are not interchangeable and that trapped air must be bled before startup to prevent pump damage. Cylinder reassembly identifies cushion-seal and oil-groove orientation and requires the rod to remain centered so new sealing rings are not cut. Mechanical tool examples include boom-cylinder piston-nut socket P/N 75301670, seal installation kit P/N 75301657, and head installation tool P/N 75301666.

Specification and Hydraulic Data Preview

The specifications identify the IVECO 8045.25.282 four-cylinder, direct-injection, turbocharged diesel engine with a displacement of 3,907 cm³, together with its starting, charging, and intake-air-heater systems. Hydraulic data identifies the twin HPV050FW variable-displacement main pumps, pilot pump, control valve, swing and travel motors, parking brakes, cylinders, and the related pressure, flow, displacement, inspection, and adjustment data.

Electrical material covers fuse-box and relay locations, monitor and switch panels, intake-air-heater sequencing, starting and charging circuits, surge protection, normal and emergency engine-stop circuits, fusible links, battery and alternator checks, continuity testing, and harness diagnosis.

This set supports EX135 machine-system diagnosis and excavator-side repair, but it does not contain the separate engine workshop volume for internal IVECO overhaul. Pressurized hydraulic circuits, recoil-spring assemblies, counterweights, and raised attachments require the blocking, lifting, pressure-release, and electrical-isolation practices specified in the manuals.