Doosan G15S-2, G18S-2, G20SC-2, GC15S-2, GC18S-2 2004 Service Manual

If you are wrenching on a Doosan G15S-2, G18S-2, G20SC-2, GC15S-2, or GC18S-2 lift truck with the G420E or G424E LP engine, you already know the pain of guessing LPG regulator settings or chasing a no-start because a torque spec was wrong. I have seen too many shops burn billable hours because they relied on aftermarket summaries that skip the critical safety warnings and factory tightening sequences. That is why I keep the OEM Service Manual – the 2004 edition – on the bench. It is 88 pages of pure factory procedure, no filler, no assumptions.

Tightening Torque: Factory Specs on Page 2

Every torque value in this manual comes straight from Daewoo/Doosan. The General Information section includes a dedicated table for tightening torque – not a generic range, but specific ft-lb values for each fastener class. Whether you are installing the cylinder head or the water pump, you get the exact number. Page 2 also carries the safety warnings that most aftermarket PDFs omit: WARNING labels for LPG fuel system work, the mandatory precautions before service. Skip those and you risk a gas leak that could kill you.

Crankshaft and Cylinder Block Removal

The Removal and Installation chapter walks through the Crankshaft And Cylinder Block procedure step by step. It details the order of main bearing cap removal, the required pulling tools (listed in the SPECIAL TOOLS section), and the correct plastigage method for bearing clearance. No guesswork on the rod bolt torque – the factory value is in the spec tables. I have seen DIYers snap bolts using a common torque wrench without the proper angle; this manual tells you the exact turn-of-nut sequence.

Does This Manual Cover the LPG Fuel System?

Yes. The second half of the book (beginning with SB4136E00) is dedicated entirely to the MI-04 LP system. It covers the N-2001 Regulator/Converter, the N-CA55-500TR Air/Fuel Mixer, the electronic throttle, and the SECM diagnostics. There is a full chapter on LPG fuel tank installation – including filler valve and quick disconnect coupling specs. If you work on LP forklifts, this section alone justifies the purchase. The advanced diagnostics chapter (Chapter 5) lists every diagnostic fault code with flash code tables. That is the difference between a two-hour diag and a twenty-minute fix.

3 Maintenance Schedules for the G420E Engine

Chapter 3 of the LPG section gives the recommended maintenance schedule. It covers: test fuel system for leaks, inspect vacuum lines, check coolant level, replace LP fuel filter element, test fuel lock-off operation, and inspect the fuel trim valve. Each task has a required tool list and a safety note. The schedule is written for hourly intervals – 500, 1000, 2000 hours – so you can plan downtime instead of reacting to failures.

System Operation: Why Heat Exchanger Flow Matters

The System Operation section explains how the cooling and lubrication systems work on these engines. Understanding the flow paths helps you diagnose overheating or low oil pressure. The manual includes a diagram of the water pump and exhaust manifold route – critical when you replace the water pump and need to know the bleed procedure. The Specification tables list service limits for cylinder bore, piston ring gap, and valve stem clearance. You cannot get those numbers from a generic engine manual.

Get the Right Torque Data from Page 2

I already mentioned the tightening torque table. Let me be specific: the values for the G420E and G424E engines differ in some places (like cylinder head bolt torque). Do not mix them up. Page 2 (safety) and the Specification section (page numbers vary by print) carry the correct numbers. Use them. I have seen a cylinder head gasket fail because someone used the spec from a similar Mitsubishi engine – that mistake cost a full rebuild.

Does this manual cover the G424E engine?

Yes. The G424E Tier II LP engine is covered in the same manual – specifications and procedures are listed separately.

What is the difference between the G420E and G424E engine service specifications?

The G424E has a larger displacement and different compression ratio. This manual provides separate specification tables for each engine, including cylinder bore diameter, piston ring end gap, valve timing, and idle speed. Do not assume interchangeability – the torque values for main bearing caps and connecting rod bolts are engine-specific. The manual also includes wiring diagrams and diagnostic fault codes unique to the G424E SECM calibration. If you service both engines, you need this single book to avoid mistakes.

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• Doosan D33S, D35C, D20/25/30S, G20/25/30P-5 2008 Service Manual”>Doosan D33S, D35C, D20/25/30S, G20/25/30P-5 2008 Service Manual

When you need the factory procedure for a job on these Doosan LP lift trucks, stop chasing links from forums. Manual Transmission”>Manual Transmission rebuilds require precise specs – so do LPG regulators. Download the Factory Manual now and keep it on your tablet or printed on the bench. Your time and your safety depend on it.