Description

Komatsu HD320, HD325 Parts Catalog – Factory OEM, No Aftermarket Guesswork

I’ve pulled enough wrenches on heavy equipment to know the difference between a manual that saves your Saturday and one that leaves you hunting for a bolt that doesn’t exist. This Komatsu HD320, HD325 Parts Catalog is the real deal – 690 pages direct from the factory, not some scanned-and-cropped aftermarket mess. You want to rebuild the fuel system on an HD320? The FUEL SYSTEM section under Chapter 11 walks you through every component with OEM part numbers. No guesswork, no “this might fit”.

Look, I’ve seen guys torque a cylinder head on a KT1150 using a general chart they found online. Then they wonder why it leaks oil at 200 hours. This manual gives you the factory spec for the NTA855 and KT1150 engines – exact torque sequences, tightening angles, and part callouts. Page 13 covers the mounting procedure for the engine assembly. If you skip to page 13-60 for the cylinder head torque values, you’ll see the factory numbers laid out. Follow them.

Engine Related Component – Fuel System Details

Chapter 11 (STRUCTURE AND FUNCTION) breaks down the engine mounting, radiator, air intake, exhaust, and the fuel system. Fuel system routing, injector clearances, and the PT pump dismounting procedure are all there. For the HD320, you get the injector and valve clearance adjustment steps under ADJUSTING INJECTOR AND VALVE CLEARANCE(HD320). For the HD325, the KT1150 injector work is separate – ADJUSTING INJECTOR AND VALVE CLEARANCE(HD325). Don’t swap the values. They’re not the same. I’ve seen it done. Don’t be that guy.

Testing and adjusting section (Chapter 12) lists the standard values for compression pressure, belt tension, and lubrication system testing. Tools for testing and adjusting are listed right after the standard values – get your feeler gauges and dial indicators ready. The manual even tells you the barring procedure for HD325 (BARRING (HD325)) – something most aftermarket PDFs skip entirely.

Disassembly and Assembly – NTA855 and KT1150 Engines

Chapter 13 covers disassembly and assembly for both engine variants. For the HD320 (NTA855): starting motor, alternator, PT pump, air compressor, engine oil cooler and oil filter, water pump, after-cooler, turbocharger, injector, cylinder head, and engine. Each component has a dismounting and mounting section. The PT pump dismounting steps are numbered – don’t skip the fuel line depressurization warning. For the HD325 (KT1150): same components but different torque specs and clearances. The cylinder head mounting sequence for the KT1150 is not the same as the NTA855. Check the page numbers: Komatsu HD325 Electrical Schematic – 481 Pages Factory OEM PDF covers the wiring, but for the mechanical side, stick to this catalog.

Power Train – Torque Converter and Transmission Breakdown

Section 20 dives into the power train. Structure and function of the output shaft, propeller shaft, torque converter, Torqflow transmission, control valve, and rear axle. Transmission hydraulic system diagrams for HD320-3 and HD325-3 are included – not generic schematics, but actual circuit diagrams with solenoid valve positions. If you’re troubleshooting a no-move condition, start with TRANSMISSION HYDRAULIC SYSTEM CIRCUIT (HD320-3) on page 21-6. The standard value for testing and adjusting the transmission includes measuring oil levels and lever operating force. The manual also covers the parking brake component parts – useful when that brake won’t release after sitting all winter.

For the rear axle, the differential component parts are listed with OEM numbers. The final drive system and rear brake components are in separate sub-sections. I’ve used these diagrams to order parts for a HD325 that had a blown final drive seal – the part number matched exactly. No returns.

Source Validity – Why OEM Beats Aftermarket Every Time

This is a factory Komatsu publication – SEBM0566D03 revision 3. The revision list on page 2 shows exactly which pages were updated (00-1 with mark ③, etc.). You won’t find that level of traceability in a third-party reprint. Aftermarket catalogs often combine multiple model years into one generic list, then you order a water pump that doesn’t clear the frame. This catalog is model-specific: HD320-3 serial 2501 and up, HD325-3 serial 1501 and up. If you want to understand the difference between a PT pump for an NTA855 and a KT1150, read this Wikipedia article on diesel engines for background, but for part numbers and torque specs, only the OEM paper matters.

Related manuals you’ll need in the shop: FAI Komatsu 67-80DT Parts Catalog – OEM Hydraulic Steering Piston List and Komatsu WH609-1 WH613-1 Parts Catalog | 347 Pages OEM. Both are factory documentation, not aftermarket reprints.

FAQ

Is this the same as the shop manual for HD320-3 and HD325-3?

This is the parts catalog with exploded-view diagrams and OEM part numbers, but it also includes service sections like testing and adjusting (Chapter 12) and disassembly/assembly steps (Chapter 13). Think of it as a combined service guide and parts book.

Does it cover the fuel system?

Yes. The FUEL SYSTEM section under Chapter 11 covers fuel lines, tank, filters, and the PT pump. Injector adjustment procedures are in Chapter 12 for both HD320 and HD325.

What serial numbers are covered?

HD320-3 from serial 2501 and up, HD325-3 from serial 1501 and up.

Are the torque specs given in foot-pounds or Newton-meters?

Both. The manual lists standard values in imperial units (ft·lb) and metric equivalents. For example, cylinder head torque for the KT1150 is given in ft·lb. Always verify your wrench setting.

If you’re tired of cross-referencing aftermarket databases that list twelve different part numbers for the same bolt, get the OEM source. Access the Komatsu HD320, HD325 Parts Catalog and keep a copy on your tablet. When the transmission won’t shift or the injector leaks, you’ll have the factory spec open before you break out the tools. Access the Factory Manual now.