Part of the Yanmar Repair Manuals.
With a Yanmar 2S apart on the stand, the questions come fast: what is the wear limit on that liner bore, which undersize metal do you order, and how tight do the rod bolts go before the pan goes back on. This is Yanmar's own factory service book for the 2S diesel engine, 95 pages of the maker's maintenance standards instead of forum guesswork, which matters when you are the only mechanic in the room and there is no one left to ask.
Inside are the maintenance standards and wear limits for the main parts, full disassembly and reassembly procedures, and dedicated coverage of the fuel injection pump, governor, injection timing, injection valves, cylinder head, liners, and the cooling water and lubricating oil pumps. A countermeasures chapter matches symptoms to causes when the engine runs rough.
It arrives as a 6.31 MB PDF you can print for the bench, so the clearances and torque figures are in front of you before anything goes back together, and the undersize and oversize metal lists mean you order the right bearing set the first time.
What's Inside This Yanmar 2S Manual
| System | Pages | Key Topics |
|---|---|---|
| Preface | 5 | |
| Outline of Major Structures | 6 | Cyl. Block, Cyl. Head, Crankshaft, Piston, Lub. Oil Pump, Fuel Injection Pump |
| Fuel and Lubricating Oil | 7-19 | Fuel (Light Oil, Heavy Oil, Quality Fuel Oil, Properties of Fuel & Engine Performances, Cautions on Fuel) |
| Periodical Checking & Servicing | 20-26 | 3-1.Periodical List of Items to Be Checked and Frequency of Checks, 3-2.Checking Locations, 3-3.Checking Locations by Systems |
| Maintenance Standards of Main Parts | 27-32 | 4-1.Maintenance Standards, 4-2.List of Measuring Positions, 4-3.List of Wear Limit, 4-4.List of Undersize Metals, 4-5.List of Oversize Metals |
| Engine Disassembly | 33-51 | 5-1.Precautions Prior to the Disassembly of the Engine, 5-2.General Cautions for Maintenance and Cleaning, 5-3.Cautions for Disassembling the Engine, 5-4.Procedure on Disassembling |
| Engine Reassembly | 52-69 | 6-1.Cautions for Reassembling the Engine, 6-2.Procedure on Reassembling |
| Disassembly & Reassembly of Other Parts | 70-91 | Fuel Injection Pump, Governor, Fuel Injection Time, Fuel Injection Valve, Air Venting of Fuel Injection System, Cylinder Head, Piston Pin and Connecting Rod, Cylinder Liner |
| Countermeasures to Engine Troubles | 92-93 | Lubricating Oil Issues, Fuel System Malfunctions, Mechanical Wear, Compression Problems, Cooling System Failures, Governor Control Issues |
| Storing Engine | 94 |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Cylinder head bolt locking torque | 15 kg/m | p. 60 |
| Fuel injection pressure | 160 kg/cm² | p. 76 |
| Normal oil pressure | 2 ~ 2.5 kg/cm² | p. 88 |
| Diesel Light Oil Cetane Number | over 45 | p. 7 |
| Engine Oil Exchange Interval (after second) | 100 hours | p. 18 |
| Cylinder Liner Inner Diameter Wear Limit | +0.030 mm | p. 27 |
| Connecting Rod Bolt Locking Torque | 6 kg/m | p. 59 |
| Cylinder Head Locking Torque | 15 kg/m | p. 60 |
| Valve Head Clearance (Suction & Exhaust) | 0.2mm | p. 82 |
| Cooling Water Pump Standard Delivery | 544 ℓ/1800 rpm-1 hr | p. 87 |
| Lubricating Oil Pressure (Normal) | 2~2.5 kg/cm² | p. 89 |
| Lubricating Oil Pump Backlash | 0.08~0.16mm | p. 91 |
Yanmar 2S Common Problems This Manual Covers
Hard starting after fuel work
Crack a line or run the tank dry and a small diesel like the 2S will crank without firing until every bubble is out. The manual's air venting procedure for the fuel injection system takes you through bleeding in order, from pump to injection valve.
Manual Section: 7.Disassembly & Reassembly of Other Parts p. 70Smoky exhaust and weak injection
A tired injection valve dribbles instead of atomizing, and the engine answers with smoke and rough running. The manual gives the pop test procedure and states that 160 kg/cm² at the moment of injection is normal, so you can condemn or pass an injector with numbers instead of guesswork.
Manual Section: 7.Disassembly & Reassembly of Other Parts p. 70Low compression from liner wear
Long hours polish the liner bore until compression bleeds past the rings and cold starts get slow. The maintenance standards chapter lists measuring positions, wear limits, and the undersize and oversize metal tables you need to decide between reringing and a liner job.
Manual Section: 4.Maintenance Standards of Main Parts p. 27Low oil pressure when warm
Pressure that sags once the oil heats up points at the pump or the pressure adjusting valve. The manual covers disassembly of the lubricating oil pump and adjustment of the pressure valve so the gauge reads 2 to 2.5 kg/cm² with the engine warm.
Manual Section: 7.Disassembly & Reassembly of Other Parts p. 70Overheating under load
Cooling trouble on a water cooled diesel shows up as climbing temperature and lost power, and the causes range from the water pump to plain neglect. The countermeasures chapter tables cooling system failures against their likely causes so you chase the right one first.
Manual Section: 8.Countermeasures to Engine Troubles p. 92Surging idle and hunting governor
An engine that will not hold a steady speed is usually a governor problem, not a fuel quantity problem. The troubleshooting chapter covers governor control issues, and the manual also carries the governor adjustment procedure itself.
Manual Section: 8.Countermeasures to Engine Troubles p. 92Head gasket leaks after a rebuild
A head pulled down unevenly or under torqued will weep compression into the coolant within hours of first start. The reassembly procedure gives the cylinder head locking torque of 15 kg/m so the head goes down right the first time.
Manual Section: 6.Engine Reassembly p. 52Frequently Asked Questions
Which engine does this manual cover?
The Yanmar 2S diesel engine. It is the factory service manual, 95 pages in English, covering fuel and lubricating oil requirements, periodic servicing, maintenance standards, full disassembly and reassembly, injection equipment, troubleshooting, and engine storage.
Does it include torque specs for reassembly?
Yes. The Engine Reassembly section gives the figures in the procedure itself, including a cylinder head locking torque of 15 kg/m and a connecting rod bolt locking torque of 6 kg/m, applied in order as the engine goes back together. p. 52
How do I bleed air out of the fuel system?
Section 7 includes a dedicated air venting procedure for the fuel injection system, alongside service of the fuel injection pump, injection timing, and the injection valves, so you can get a hard starting 2S firing again after fuel work. p. 70
Does it help me diagnose problems, not just repair them?
Yes. The Countermeasures to Engine Troubles chapter tables faults against causes, covering lubricating oil issues, fuel system malfunctions, mechanical wear, compression problems, cooling system failures, and governor control issues. p. 92
What format is this manual in?
A 95-page Service Manual in searchable PDF format (6 MB), available the moment you complete checkout. View on computer, tablet, or phone, with no shipping wait.
Am I able to print pages from this manual?
Zero restrictions. The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
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