Description

Komatsu 108 1998 Workshop Manual – Factory Diesel Engine Specs

Let me be clear: if you are tearing into a Komatsu 108 1998 Workshop Manual engine, you need the real OEM documentation – not some reprint from a third party that got the clearances wrong and left out half the troubleshooting steps. I have seen guys in my shop waste an entire afternoon because they trusted an aftermarket manual that listed the wrong valve adjustment sequence. This is the factory binder, 254 pages, published in 1998 by Komatsu themselves. It covers nothing but the 108 series diesel engine, and it does it right.

You want to know what’s inside? Section 11 breaks down the entire engine body – cylinder head, cylinder block, main revolving system, timing gear, valve system, flywheel and flywheel housing. Then section 12 gives you the testing and adjusting procedures: adjusting valve clearance, measuring compression pressure, testing and adjusting fuel injection timing. Section 14 is the maintenance standard – all the wear limits for pistons, rings, cylinder liners, crankshaft journals. Section 15 walks you through repairs like replacing valve seat inserts, grinding the crankshaft, replacing cam bushings. That is the kind of depth you pay for when you buy the real thing.

Cylinder Head and Valve System Specs

Section 11 dives into the cylinder head and valve system – not just parts lists but the actual function. You get exploded diagrams of the rocker arm, push rod, tappet, valve guide clearances. When you flip to section 14, you find the maintenance standard for valve and valve guide: acceptable stem-to-guide clearance, valve seat width, runout limits. That section alone saves you from guessing whether a valve job is needed. And section 12 gives you the exact procedure for adjusting valve clearance – cold, with the engine at top dead center on the compression stroke. No second-guessing.

Does This Manual Cover Fuel Injection Timing?

Yes. And it does it properly. Section 12 has a dedicated sub-section for testing and adjusting fuel injection timing. You get the calibration data, the required tool list, the step-by-step for setting the injection pump timing marks. There is also a procedure for adjusting the fuel cut solenoid link and the engine stop motor cable. If you are chasing a hard-start or no-start condition, the troubleshooting chart under S-2 walks through three separate sub-causes: engine does not turn, engine turns but no fuel injected, exhaust comes out but no start. That is the kind of diagnostic logic that saves you from replacing parts you don’t need.

Troubleshooting Charts That Actually Work

The troubleshooting section in this manual runs from S-1 through S-16. Poor starting, no start, lacks power, black smoke, blue smoke, overheating, abnormal noise, vibration – every common failure mode for a diesel engine. Each chart is laid out with numbered checkpoints. You start at step 1, follow the yes/no branches, and end at the root cause. I have used these charts on 108 engines that came in with mysterious oil-in-water problems (S-11) and tracked it to a failed oil cooler core in under an hour. You cannot do that with a generic manual.

Komatsu 108 1998 Workshop Manual: What’s Inside the 254 Pages

Here is what you get beyond the obvious: section 1 (General) gives you the engine performance curve, weight table, and overall specs. Section 11 covers the entire structure and function – intake and exhaust system (after-cooler, turbocharger, air cleaner, electronic dust indicator), lubrication system (oil pump, filter with built-in safety valve, oil cooler), fuel system (injection pump, nozzles, filter, drive case, stop motor, cut solenoid), cooling system (thermostat, water pump), and electrical system (wiring diagram, alternator, starting motor, glow plugs). Section 13 is disassembly and assembly – the correct order for pulling the engine down and putting it back together to avoid bending valves or cocking the crank. Section 14 gives you the maintenance standard for every component: turbocharger, cylinder head, valve and valve guide, rocker arm, push rod, tappet, cylinder liner, cylinder block, crankshaft, camshaft, piston, piston ring, piston pin, connecting rod, timing gear, flywheel, oil pump, regulator valve, safety valve, water pump, thermostat. Section 15 goes into repair and replacement: grinding the cylinder head mounting face, replacing valve seat inserts, pressure testing, replacing valve guides, grinding valves, replacing cam bushings, crank gear, cam gear, flywheel ring gear, main bearing cap, grinding crankshaft, replacing engine rear seal. Every page number is referenced in the list of revised pages so you know you have the latest updates.

Why OEM Factory Documentation Matters

I have been running a six-bay shop in San Antonio for over 28 years. The difference between an OEM manual and an aftermarket PDF is the difference between a head gasket that holds 200 psi and one that leaks coolant into the oil pan after fifty hours. The Komatsu factory manual lists actual torque values, actual clearance limits, actual calibration data. The aftermarkets take shortcuts – they reuse diagrams from other engines, they leave out the built-in safety valve in the oil filter, they don’t tell you that the fuel injection pump drive case has a specific timing mark alignment. That is why I buy only OEM workshop manuals from this site. For the 108 series, this is the only manual you need. If you are also working on a different machine, check out the Komatsu WA65-5 WA70-5 WA80-5 2005 Workshop Manual or the Komatsu WH609-1E0 WH613-1E0 WH713-1E0 WH714H-1E0 WH716-1E0 Workshop Manual or the Komatsu PW95R-2 Workshop Manual – 520 Pages of Factory Specs. For general background on how manual transmissions work when you are pulling an engine, Wikipedia has a solid overview of Manual Transmission Manual Transmission and again Manual Transmission Manual Transmission but for engine work, you stick with the factory sheets.

Is this manual specific to the Komatsu 108 engine?

Yes. It covers only the 108 series diesel engine, not other models.

Can I use this manual for a different engine model?

No. This manual is specific to the Komatsu 108 series. Using it for another engine will give you wrong torque values and clearances. The 254 pages are engineered for this exact engine – cylinder head bolt torque, valve lash, injection timing, compression pressure limits. I have seen mechanics try to adapt specs from a 98 to a 108 and end up with a blown head gasket. The aftermarket might re-brand it as a universal diesel manual, but this OEM document is not. Don’t guess – get the right manual for your engine. The troubleshooting charts alone are tailored to the 108’s fuel system and turbocharger layout. A different engine has different failure patterns. Save yourself the trouble.

If you are rebuilding or repairing a Komatsu 108 series diesel engine, stop messing with copied scans and vague internet tables. Get the actual factory binder that Komatsu engineers wrote and signed off on. There is a reason this engine has been running in loaders, excavators, and industrial equipment for decades – it is a solid design when you follow the factory specs. Access the Factory Manual and keep it on your bench. Your torque wrench and your cylinder head will thank you.