Mitsubishi S12H Diesel Engine Service Manual (tp6852)

These S12H engines usually live in hard service—generators, pumps, or industrial drives running long hours in dusty, hot, or coastal environments. This service manual is what I’d pull out when I need to prove what’s wrong before ordering expensive parts or tearing deep into the engine. For example, if the unit is hard-starting with white smoke, I’d use this book to trace the fuel system step by step, verify timing and clearances, and confirm it’s a real mechanical issue, not just bad fuel or a simple adjustment.

Applications & Use Cases

Trace low power complaints by following the manual’s diagnostic flow to isolate fuel, air, or timing faults.
Inspect and rebuild major components using the disassembly/assembly sequences so nothing goes back misaligned.
Verify adjustments on valve train, linkages, and controls after an overhaul or head job.
Route and secure hoses, pipes, and wiring correctly after a strip-down, avoiding rub points and leaks.
Test and confirm repairs under load using the manual’s checks so the engine is right before returning it to service.

FAQ

Q: Is this manual practical to use on a tablet in the field?

A: Yes, it works well digitally; you can zoom diagrams and search terms instead of flipping pages with greasy hands.

Q: Should I still print sections of it?

A: I recommend printing the procedures you’re using that day so you can mark notes and keep it next to the engine.

Safety Note

Always lock out the driven equipment and disable starting circuits before working on or near the rotating parts of this engine.

📘 Show Index

Mitsubishi S12H Diesel Index:

Chapter 1 GENERAL
1. External View
2. Outline of Systems
3. Contents of Plate and Label
4. Specifications
Chapter 2 SERVICE DATA
1. Maintenance Service Data
2. Tightening Torque Table
Chapter 3 SERVICE TOOLS
1. Special Tools
Chapter 4 OVERHAUL INSTRUCTIONS
1. Determining Overhaul Timing
2. Compression Pressure – Measure
Chapter 5 DISASSEMBLY OF BASIC ENGINE
1. Cylinder Head and Valve Mechanism – Disassemble and Inspect
2. Rear Mechanism – Disassemble and Inspect
3. Front Mechanism – Disassemble and Inspect
4. Cylinder Liner, Piston and Connecting Rod – Disassemble and Inspect
5. Crankcase, Crankshaft and Main Bearing – Disassemble and Inspect
Chapter 6 INSPECTION AND REPAIR OF BASIC ENGINE
1. Cylinder Head and Valve Mechanism – Inspect and Repair
2. Rear Mechanism – Inspect and Repair
3. Front Mechanism – Inspect and Repair
4. Piston and Connecting Rod – Inspect and Repair
5. Crankcase and Crankshaft – Inspect and Repair
Chapter 7 ASSEMBLY OF BASIC ENGINE
1. Crankshaft and Main Bearing – Install
2. Cylinder Liner, Piston and Connecting Rod – Assemble
3. Front Mechanism – Assemble
4. Rear Mechanism – Assemble
5. Cylinder Head and Valve Mechanism – Assemble
Chapter 8 FUEL SYSTEM
1. Fuel System – Remove and Inspect
2. Fuel System – Disassemble, Inspect and Assemble
3. Fuel System – Install
Chapter 9 LUBRICATION SYSTEM
1. Lubrication System – Remove and Inspect
2. Lubrication System – Disassemble, Inspect and Assemble
3. Lubrication System – Install
Chapter 10 COOLING SYSTEM
1. Cooling System – Remove and Inspect
2. Cooling System – Disassemble, Inspect and Assemble
3. Cooling System – Install
Chapter 11 INLET AND EXHAUST SYSTEMS
1. Inlet and Exhaust Systems – Remove and Inspect
2. Inlet and Exhaust Systems – Disassemble, Inspect and Assemble
3. Inlet and Exhaust Systems – Install
Chapter 12 AIR START SYSTEM
1. Air Start System – Remove and Inspect
2. Air Start System – Install
Chapter 13 ADJUSTMENT AND OPERATION
1. Engine – Adjust
2. Break-in Operation
3. Engine-Test and Adjustment
4. Seal (MUI)