Scania DI12 350, 300 Series Engine Service Manual (TP6674)

These DI12 engines usually live in tough service—buses, construction gear, marine or industrial sets running long hours in heat, dust and vibration. This service manual is what I reach for when I need to prove what’s actually wrong before pulling parts. For example, if a DI12 starts hard and smokes under load, I’ll use this book to trace the fault step by step through fuel, air and timing checks instead of guessing at injectors or pumps.

Applications & Use Cases

• Track down performance issues by following the diagnostic logic to isolate fuel, air, or mechanical faults.
• Plan disassembly and reassembly of major components so you don’t miss seals, shims, or alignment steps.
• Verify adjustments on valve gear, linkages, and brackets after a repair to avoid repeat failures.
• Confirm wear limits visually so you know when to reuse, recondition, or replace parts.
• Support parts identification by matching what you see on the engine to the correct component layout and fastener locations.

FAQ

Q: Can I use this manual on a tablet in the workshop?

A: Yes, it works well digitally; you can zoom diagrams and search text, just keep the device protected from oil and dust.

Q: Is it worth printing sections of this manual?

A: I often print the pages for the job I’m doing so I can mark measurements, notes, and torque sequences right beside the engine.

Safety Note

Always lock out the machine and follow Scania’s safety instructions before opening, rotating, or testing any part of the engine.

Scania DI12 350, 300 Series Index:

Contents
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page
SI Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Markings on bolts and nuts . . . . . . . . . . . . . . . . 8
Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bolted joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Left-hand threads. . . . . . . . . . . . . . . . . . . . . . . . 8
Tightening torques . . . . . . . . . . . . . . . . . . . . . . 6 Hexagon bolts . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Angle tightening . . . . . . . . . . . . . . . . . . . . . . . . 7 Generael tightening torques . . . . . . . . . . . . . . . 9
Retightening . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Union assemblies and plugs . . . . . . . . . . . . . . . 9
Re-use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Thread inserts . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Engine oil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Oil grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Oil analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Diesel fuel (diesel fuel oil) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Requirements and testing norms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Fuel properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Formula for calculation of engine output . . . . . . . . . . . . . . . . . . . . . 10
Water and micro-organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Grades of diesel fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Alternative fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
RME (Rape Methyl Ester) fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Coolant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Coolant composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Low temperature properties of the coolant . . . . . . . . . . . . . . . . . . . . 16
Dosage table for glycol anti-freeze . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Internal cleaning of cooling system. . . . . . . . . . . . . . . . . . . . . . . . . . 18
Summary of volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Lubricating oil volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Coolant volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 and more

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