Part of the Yanmar Parts Manuals.
A crankshaft going back into its block on journals ground 0.25 undersize is only as reliable as the bearing number ordered against it, and guessing that number from a lookalike engine is how a fresh rebuild spins a shell in its first hour. These 49 pages exist to stop that: the Yanmar parts catalog for the 3TN84L-RBB diesel, publication Y00B4421, covering the engine from cylinder block to suction and exhaust manifold.
Seven sections break the engine into its assemblies: Cylinder Block, Gear Housing, Flywheel Housing, Lub.Oil Sump, Bonnet, Cylinder Head, and Suction & Exhaust Manifold. Each lists the seals, gaskets, bearings, bushes and hardware by Yanmar part number, so whether this engine sits in a tractor, a genset, or on a stand, you order once and order right.
The PDF is 0.7 MB, downloads immediately, and prints clean, so the pages can sit on the bench beside the parts they name.
What's Inside This Yanmar 3TN84L-RBB Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Cylinder Block | 3-4 | Plug PT1/4, Bolt, Bearing Cap, Main Bearing, Bearing, Thrust, Bush, Camshaft |
| Gear Housing | 5-6 | Seal, Oil, Stud M 8X 22, Cap, LUB.OIL Supply, Flange, Gears Housing, Gasket |
| Flywheel Housing | 7-8 | Parallel Pin 8X16, Housing, Flywheel, Cap, Flywheel Cover, Case Assy, Oil Seal, Seal |
| Lub.Oil Sump | 9-10 | Sump Assy, Lub Oil, Cover, Oil Sump, Plug M16, Seal Washer 16S, Bolt M |
| Bonnet | 11-12 | - |
| Cylinder Head | 13-14 | - |
| Suction & Exhaust Manifold | 15-49 | - |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Undersize | 0.25 | p. 2 |
| Thrust Bearing Undersize | 0.25 | p. 2 |
| O-RING 1A P-16.0 | 16.0 | p. 4 |
| O-RING 1A P-32.0 | 32.0 | p. 4 |
| O-RING 1A P-26.0 | 26.0 | p. 4 |
| O-RING 1A S-24.0 | 24.0 | p. 4 |
| O-RING 1A P-32.0 (Bonnet) | 32.0 | p. 10 |
| O-RING 1A S-50.0 | 50.0 | p. 10 |
| O-RING 1A P 12.0 | 12.0 | p. 10 |
| V-BELT (A-38) | 38 | p. 26 |
| V-PULLEY Diameter | 110 | p. 26 |
| O-RING 1A G-65.0 | 65.0 | p. 37 |
Yanmar 3TN84L-RBB Common Problems This Manual Covers
Low Hot Oil Pressure From Bearing Wear
Worn main bearings let hot oil pressure sag at idle long before the crank starts knocking. The Cylinder Block section lists the main bearings and bearing caps, including 0.25 undersize shells, so a reground crankshaft goes back together on the correct parts instead of a guess.
Manual Section: Cylinder Block p. 3Excessive Crankshaft Endplay
Endplay you can feel with a pry bar means the thrust faces are gone, and a clutch or coupling load will make it worse fast. The thrust bearing, including its 0.25 undersize, is listed in the Cylinder Block section.
Manual Section: Cylinder Block p. 3Oil Leak at the Front Gear Housing
A wet timing gear case and oil tracking down the front of the engine usually comes back to the front oil seal or a tired housing gasket. The Gear Housing section lists the oil seal, gasket, studs, and the lube oil supply parts behind that cover.
Manual Section: Gear Housing p. 5Oil Weeping Into the Flywheel Housing
Oil collecting inside the flywheel cover points at the rear oil seal, and on this engine that means the flywheel comes off. The Flywheel Housing section lists the oil seal, housing, cover, and case assembly so every part is on hand before teardown.
Manual Section: Flywheel Housing p. 7Stripped Sump Drain Plug or Weeping Washer
Reused crush washers and overtightened drain plugs are how sumps end up weeping onto the floor between oil changes. The Lub.Oil Sump section lists the sump assembly, the M16 plug, and the 16S seal washer by part number.
Manual Section: Lub.Oil Sump p. 9Head Gasket Failure and Compression Loss
Coolant in the oil or bubbles in the header tank on a small diesel usually ends at the head gasket. The Cylinder Head section carries the head hardware listings you need to order the top end correctly before the head goes back on.
Manual Section: Cylinder Head p. 13Exhaust Leak at the Manifold
A ticking exhaust leak under load, or an intake joint pulling unfiltered air, means the manifold gaskets and fasteners are due. The Suction & Exhaust Manifold section is the largest in the catalog and lists that hardware by part number.
Manual Section: Suction & Exhaust Manifold p. 15Frequently Asked Questions
Which engine does this parts catalog cover?
The Yanmar 3TN84L-RBB diesel engine, Yanmar publication Y00B4421, in English, 49 pages. It covers the engine itself, so it applies whatever the engine is installed in, and runs from the Cylinder Block section through Suction & Exhaust Manifold.
Is this a service manual with torque specs and clearances?
No. This is the parts catalog: it identifies components by Yanmar part number for ordering, section by section. It does not give the cylinder head torque sequence, valve lash, or bearing clearance procedures; you would pair it with a service manual for rebuild specs.
Does it list undersize bearings for a reground crankshaft?
Yes. The Cylinder Block section lists 0.25 undersize main bearings and a 0.25 undersize thrust bearing alongside the standard shells, so you can order shells that match the machined journals rather than guessing from a standard-size number. p. 3
Can I find part numbers for the oil seals?
Yes. The Gear Housing section lists the front oil seal and its gasket, and the Flywheel Housing section lists the rear oil seal along with the housing and cover parts, so both ends of the crankshaft are covered. p. 5
What do I get after purchasing this Yanmar 3TN84L-RBB manual?
You get a 49-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Can I print specific sections of this Yanmar 3TN84L-RBB Parts Catalog?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
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