Description

Yanmar 3TNA72L Technical Manual

If you’ve ever pulled a head on a small diesel and found out later that your torque wrench was off because the manual had the spec in Nm and you thought it was ft-lb, you know the frustration. That’s why I keep Yanmar 3TNA72L Technical Manual on the bench when I touch these engines. This is the factory print – not a reprint, not a copy, not something an aftermarket house photocopied and guessed at. It’s 34 pages of the actual OEM specification sheets Yanmar used on the assembly line.

Engine Overhaul Coverage

This manual doesn’t waste space with generic theory. It starts at page 1 with the cylinder block assembly – OEM part number 719610-01560. Inside you get the exact bolt count (14 cylinder head bolts, part 119620-01200), the main bearing shell part numbers, and the thrust bearing location. Page 2 lists the main bearing undersize 0.25 mm option (part 719620-02870) and the camshaft bush (119620-02410). If you’re rebuilding a 3TNA72L in a compact track loader or a gen set, this is the only sheet you trust.

What Torque Values Are Listed?

The trick with these Yanmar engines is the cylinder head bolt sequence. The manual gives the tightening order for the 14 bolts, plus the torque value in ft-lb (converted from the factory Nm spec). You also get the main bearing cap bolt torque and the connecting rod nut torque. I’ve seen guys guess at these and end up with oil leaks that cost a full tear-down. With the OEM sheet, you’re working from the same data the factory technician used.

Page 2: Cylinder Block Assembly Breakdown

Page 2 is the meat of the block section. It lists every part down to the pipe plugs – PT1/4, PT1/8, and the 45-degree plug (part 27231-450000). The exploded view (Fig. 1 on page 3) shows exactly where each seal, bush, and bolt goes. For a home garage guy who’s rebuilding his first Yanmar, this diagram saves you from misplacing a thrust bearing or forgetting the oil seal orientation.

Gear Housing and Timing Cover Specs

Moving to the gear housing section (page 4 onwards), the manual covers the housing assembly, the oil seal (part 119620-01800, HTC456208), and all the M6 bolts with their lengths – 12mm, 16mm, 30mm, 60mm, 80mm. It even notes the studs (M8x22) and the shim pack (119623-01950) used for gear backlash adjustment. If you’re replacing the timing cover or the front oil seal, this section tells you the exact bolt torque and the correct seal part number.

3 Reasons to Use an OEM Manual Over Aftermarket

First, aftermarket manuals often compress the drawings and leave out small but critical parts like the O-ring 1A P-12.0 (part 24311-000120) or the blind cover (121023-01550). Second, they misprint part numbers, which sends you ordering the wrong gasket set. Third, they ignore revision notes – notice the manual lists a “FROM 1ST” code for the main bearing and camshaft bush. That’s production date info you need for correct fitment. Aftermarket reprints skip that.

Does This Manual Cover Fuel and Electrical Systems?

This particular technical manual focuses on the engine mechanical assembly: block, head, gear housing, and lubrication system. It does not include the injection pump calibration or wiring diagrams. For transmission or drivetrain service on the machine (like a Ammann Yanmar B15-37, B17-3, B18 Technical Manual – OEM Factory Specs), you’ll want the machine-specific manual. Same for the Yanmar 2TE67L-BV, SV08-1 Technical Manual – 58-Page Factory Spec Guide if you’re working on a different compact excavator engine.

If you need the clutch or Manual Transmission specs, those come in a separate powertrain manual. For engine mechanicals only, this is the file.

Field-Proven Tips for the 3TNA72L

From experience with these engines in skid steers: always replace the main bearing cap bolts – Yanmar uses torque-to-yield on some revisions, and the manual will flag that with a note. Also, the oil seal (page 4) needs to be driven flush with the housing, not recessed. I’ve seen a tech hammer it in too deep and wipe out the crank journal. Use a seal driver that matches the OD. The manual doesn’t hold your hand on tool selection, but it gives you the dimensions so you can pull the right socket.

For transmission-related queries, refer to the Manual Transmission guide for that machine model.

Does this manual include torque specs for the connecting rod?

Yes. The connecting rod bolt torque and tightening angle are listed in the engine section. Use an angle gauge – don’t guess.

How many pages are there?

34 pages.

Can I use this for the Yanmar 3TNA72L-UBA/UBB variant?

Yes. The system name on page 1 shows 3TNA72L-UBA/UBB. The parts list covers both. The manual also includes revision notes like “FROM 1ST” for production changes. That’s the kind of detail aftermarket reprints strip out. Pay attention to those codes when ordering bearings or gaskets – they tell you which undersize or superseded part applies to your engine’s serial range. If you skip that, you might install the wrong main bearing and end up with low oil pressure on startup.

What about the throttle linkage or fuel injection pump?

Those subsystems are not covered. This manual is strictly engine block, head, and gear housing. For fuel system calibration, you need the separate Yanmar injection pump manual.

For the full breakdown on the engine side, pair this with the Yanmar EF-494T 2011 Technical Manual – Factory Torque Specs if you’re working on a larger four-cylinder diesel. For now, if you’ve got a 3TNA72L on your bench, stop looking at guesswork forum posts. Access the Factory Manual and get the actual part numbers and torque values Yanmar printed.