Mitsubishi S6S Diesel Engine Forklift OEM Service Manual (P/N 99709-56110)

• S6S engine overhaul covers cylinder heads, pistons, connecting rods, crankshafts, and tappets, with timing-gear, camshaft, and valve-train inspection and assembly procedures.
• Engine diagnosis extends to compression testing, injection timing, nozzle calibration, and governor adjustment, followed by break-in and performance checks after overhaul.
• Dry and wet clutch repair for FD35/FD40/FD45 includes release mechanisms, hydraulic controls, adjustment, and bleeding. The manual-transmission sections cover synchromesh gears, shafts, and shifter assemblies.
• Powershift coverage includes torque converters, clutch packs, control valves, inching adjustment, and pressure testing, with separate sections for single-speed and automatic two-speed transmissions.
• Chassis procedures address differential and axle repair, Mastervac brake-booster testing, drum-brake service, and recirculating-ball steering-gear and power-cylinder overhaul.
• Hydraulic repair covers pumps, control valves, lift and tilt cylinders, leakage checks, and relief-valve adjustment. Dual-stage panoramic mast service includes rollers, lift chains, and carriage clearances.
• Separate Electrical System Schematic (Diesel Models) and Electrical System Schematic (Gasoline Models) drawings accompany combination-meter, OK monitor, sensor, relay, and starting-system fault diagnosis.

Three Manuals with Different Model Coverage

This Mitsubishi service manual set contains 693 PDF pages across three documents.

The 142-page manual 99709-56110 covers the S6S diesel engine in FD35 through FD50, FD60, and FD70 forklifts. Publication No. 99709-56120, a 149-page PDF, covers FD40K, FD40KL, FD45K, FD50K, FD60, and FD70, with its S6S engine coverage identified as engine serial number 28620-up.

The 402-page Chassis & Mast manual, Publication No. 99739-74100, covers FD35, FD40, FD45, FD50C, FD50, FG35, and FG40. Listed diesel chassis ranges include FD35 F19B-00011-up, FD40 F19B-50001-up, and FD50C/FD50 F28A-50001-up.

FD60/FD70 and K-series coverage is engine-only in this set. FG35/FG40 coverage concerns chassis systems on trucks with the 6G72-32FD gasoline engine; internal gasoline-engine overhaul is outside the set’s scope.

S6S Engine Systems and Rebuild Details

Internal repair procedures cover valve-seat refacing, valve-guide replacement, cylinder-bore inspection and honing, crankshaft regrinding, and bearing selection. The Valve timing diagram and timing-gear marks support mechanical setup during assembly.

Lubrication coverage includes oil pump inspection and rebuild, oil pressure relief valve testing, and oil-filter service. Cooling-system sections cover centrifugal water pump inspection and replacement, along with thermostat testing. Starter and alternator inspection receive their own sections; the serial-specific engine volume also includes stop-solenoid checks.

Fuel-system coverage addresses the Bosch A injection pump, Bosch RSV governor, filter maintenance, and injection-nozzle testing. Internal injection-pump and governor overhaul belongs to separate volumes, rather than these engine books.

Configuration details include single-lip rear crankshaft seals for dry-clutch and torque-converter applications versus double-lip seals for wet-clutch applications. Repair cautions also identify rocker-shaft bracket damage caused by an incorrect bolt-loosening sequence.

Clutch Access, Shift Diagnosis, and Mast Adjustment

Power-train procedures cover engine removal alone or removal of the engine, transmission, and differential as an assembled unit. Dry-clutch disc and pressure-plate replacement are covered without power-train removal; access to those parts in the enclosed wet-clutch arrangement requires engine removal.

The automatic two-speed Powershift section covers FD50C/FD50 and optional installations in FG35/FG40 and FD35/FD40/FD45 trucks. Its pulse generator, electronic control unit, and solenoid valve are addressed in shift-system descriptions and troubleshooting. A Hydraulic System Schematic documents the single-speed Powershift circuit alongside control-valve and oil-pressure test information.

Differential setup includes bearing preload, backlash, and a Tooth contact pattern adjustment chart. Hydraulic fault isolation distinguishes control-valve leakage from cylinder faults and covers loaded mast drift, lowering performance, and lift-cylinder stroke equalization.

The Mast adjustment chart supports roller selection and mast-to-carriage clearance work. The overhaul procedures focus on the dual-stage panoramic mast, with different roller arrangements for the smaller and larger chassis models. Hydraulic repair cautions explain how uneven control-valve tie-bolt tightening can distort the housings and restrict spool movement.

Precision Values and Assembly Specs

Factory reference data covers component-specific torque tables, including cylinder-head and flywheel fasteners, plus wear limits, fits, clearances, fluid capacities, and electrical test specifications. Chassis troubleshooting charts connect symptoms such as clutch slip, loss of drive, automatic-shift faults, and mast drift with possible causes and remedies.

Special-tool references identify the 30691-13010 oil-seal sleeve installer set, 91868-00500 clutch gauge, and 64309-17701 pressure-gauge kit, with the assemblies and tests each tool serves.

Rely on the complete OEM procedures and follow standard shop safety practices during teardown or rebuild, particularly for heavy engine assemblies, raised masts, and pressurized hydraulic systems.