Part of the Yanmar Parts Manuals.
Halfway through a hose swap on a Yanmar B2U-1, the job stops the moment you need one exact part number and nobody at the counter can find it. That is what Yanmar's own parts catalog, publication Y00K3631, is for: every assembly on the B2U-1 crawler backhoe laid out in exploded diagrams with the genuine part number beside each callout.
The catalog runs 280 pages and covers 1998 machines from serial number 30501, fitted with the 3TNE74-N3AY and 3TNE74-EN3AY engines (engine serials from N00177 and N04808). Engine mounts, fuel system, radiator and oil cooler, hydraulic pump and piping, control valves, wiring diagrams, electrical parts, and undercarriage each get their own diagrams, plus paint part numbers for a correct-color restoration.
Download the PDF, find your assembly through the pictorial index, and print just the page you need, so the bench copy can get greasy while the file stays clean.
What's Inside This Yanmar B2U-1 Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Preface | 1 | Parts Catalog History, Model Name, Yanmar Genuine Parts |
| Vehicle Painted Color | 2 | Painted Color, Main Parts, Under Traveling Body, Work Equipment, Canopy, Monitor |
| Paint Part No. | 3 | Painted Color, Munsell No., Color Division, Spray CAN |
| Wiring Diagram (1) | 4 | Starter, Alternator, Battery, Monitor, Fuel Sensor, Horn |
| Wiring Diagram (2) | 5 | Wiring Harness, Connector Routing, Fuse Box, Relay, Cab Harness, Ground Points |
| Picturesque Indx(1) | 6 | Engine Related Parts, Hyd. Oil System, Fuel Tank, Radiator, Oil Cooler, Electric Part |
| Picturesque Indx(2) | 7 | Operator Compartment, Control System, Canopy, Operator Seat, Floor Mat, Control Equipment |
| Picturesque Indx(3) | 8 | Under Carriage, Turning Related Parts, Travel, Swivel Joint, Track Roller, Track Frame |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Part: Spring Pin dimensions | 4mm x 8mm | p. 170 |
| Part: O-Ring 1A P-dimension | P-18.0 | p. 108 |
| Part: Shim thickness | 1.0mm | p. 170 |
| Part: Seal dimensions | 35mm x 45mm x 4mm | p. 174 |
| Part: Bulb wattage | 60W | p. 190 |
| Part: Circlip size | 52 | p. 228 |
| Part: O-Ring 1B P-dimension | P-11.0 | p. 248 |
Yanmar B2U-1 Common Problems This Manual Covers
Weak hydraulics from a worn pump
Slow cylinders and fading breakout force on older Yanmar machines often trace back to a tired hydraulic pump. The Hyd. Oil Pump diagrams identify the pump assembly and its related hardware so you order the right replacement the first time.
Manual Section: Hyd. Oil Pump p. 18Leaking hydraulic hoses and fittings
Hydraulic hoses are among the most replaced parts on these machines, and a weeping fitting can drain a tank over a season. The Hyd. Oil Piping section maps every hose, fitting, and seal in the circuit by part number.
Manual Section: Hyd. Oil Piping p. 19Cranks but will not start
Intermittent starting on a machine this age usually comes down to a weak battery, corroded terminals, or loose connections. The Battery section shows the battery, mounts, and cable hardware so you can replace the whole path, not just the symptom.
Manual Section: Battery p. 14Wiring faults and blown fuses
Electrical instability is a recurring complaint on older Yanmar excavators: dead gauges, unreliable controls, fuses that keep popping. The wiring diagram covers the starter, alternator, battery, monitor, fuel sensor, and horn circuits so you can trace the fault instead of guessing.
Manual Section: Wiring Diagram (1) p. 4Running hot under load
Overheating on these machines is commonly a clogged radiator or oil cooler, tired hoses, or failing clamps. The Radiator & Oil Cooler diagrams break out the cores, mounts, and hardware for a proper cooling system refresh.
Manual Section: Radiator & Oil Cooler p. 5Water and dirt in the fuel
Diesel contamination shows up as rough running and hard starts, and daily draining is part of life with these engines. The Drain (Fuel Tank) section identifies the drain components so you can restore a seized or leaking drain point.
Manual Section: Drain (Fuel Tank) p. 12Sticky or leaking control valve
A spool that hangs up or an internal leak makes the whole machine feel vague at the levers. The Control Valve section shows the valve assembly and its seal kit components by part number.
Manual Section: Control Valve p. 45Frequently Asked Questions
Which machines does this parts catalog cover?
It covers the 1998 Yanmar B2U-1 crawler backhoe from machine serial number 30501, with the 3TNE74-N3AY and 3TNE74-EN3AY engines (engine serials from N00177 and N04808). It is Yanmar publication Y00K3631.
Is this a repair manual or a parts catalog?
It is the factory parts catalog, not a repair manual. Its 280 pages give exploded diagrams and genuine Yanmar part numbers for every assembly, which is what you need for ordering parts, identifying hardware during teardown, and sourcing replacements for a restoration.
Does it include wiring diagrams?
Yes. Two wiring diagrams cover the starter, alternator, battery, monitor, fuel sensor, and horn circuits, starting in the Wiring Diagram (1) section. They pair with the Electric Part listings when you need to replace a component you have traced. p. 4
Does it cover the hydraulic system?
Yes. The catalog breaks out the Hyd. Oil Pump, hydraulic piping, control valve, solenoid valve, remote control valve, and hydraulic oil tank, each with its own exploded diagram and part numbers, including seals and fittings. p. 18
How quickly can I access this manual after buying?
This is a 280-page searchable PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Am I able to print pages from this manual?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
Does this Yanmar B2U-1 Parts Catalog have electrical diagrams?
A wiring diagram for the Yanmar B2U-1 electrical system is included.
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