Part of the Yanmar Parts Manuals.
A crankshaft that needs 0.25 undersize main bearings will not forgive a guessed part number, and the whole point of the 46 pages in this Yanmar parts catalog, factory publication Y00B3322, is that you never have to guess. Each section breaks an assembly into numbered parts, from the governor rack and pinion through the starter, generator, magnetic relay and the full gasket set.
It covers the 4TN78TL, 4TN78TL(YB401W), 4TNA78TL-DBWVM, 4TNA78TL-RBW and 4TN78TLL-DBWVM diesels, wherever yours happens to be installed, and bookmarked sections take you straight to the system you have on the bench.
An engine in pieces earns nothing while a wrong part rides back to the supplier. With the catalog open beside the teardown you match each worn piece to its listing, order once, and put the engine back together on your schedule instead of a parts counter's.
What's Inside This Yanmar 4TN78TL / 4TNA78TL Series Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Governor | 33-34 | Lever Bracket, Joint Retainer, Circlip, Pin |
| Control Lever Bracket | 35-36 | Starter, Pinion Stopper Set, Pinion Stopper Clip, Field Coil Assy, Pore Core Screw Set, Brush, Rear Cover Assy, Rear Cover Metal |
| Starting Motor | 37-38 | Generator, Rotor Assy, Spacer, Stator Assy, Rear Cover Assy, Regulator Brush Assy, Brush Assy, Regulator Assy |
| Generator | 39-40 | Earth Cord, Cord, Magnetic Relay, Bolt |
| Magnetic Relay | 41-42 | Dust Filter, Air Cleaner Assy, Outer Element, Cleaner Body, Air Cleaner Cup, Baffle, Inner Element, Unloader Valve |
| Tropics & Desert Type | 43-44 | Gasket Set, Cylinder Head Gasket, Hydraulic Oil Pump Gasket, Oil Seal Case Gasket, Bonnet Gasket, Suction Manifold Gasket, Exhaust Manifold Gasket, RHB31 Turbo Gasket |
| Gasket Set & Tool | 45-46 | Gasket Set, Gasket, Cyl. Head, O-Ring, HYD.OIL Pump, SUC.MANIFOLD |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Undersize | 0.25 U.S. | p. 2 |
| Bearing Pin Undersize | 0.25 U.S. | p. 16 |
| Piston Ring Set Oversize | 0.25 | p. 16 |
| V-Belt Type | A-38 | p. 22 |
| Ball Bearing Size | 13/32 | p. 18 |
| Wire Diameter | 0.6 | p. 32 |
| Governor Link Length (Mark 05) | 30.5 | p. 31 |
Yanmar 4TN78TL / 4TNA78TL Series Common Problems This Manual Covers
Hunting idle and surging under load
When engine speed wanders, the wear is usually in the governor rack, pinion and bush rather than anything you can adjust out. The Governor section lists the rack, pinion, bush and control lever by part number so you replace the worn pieces instead of chasing the symptom.
Manual Section: Governor p. 33Sloppy or seized throttle linkage
Years of vibration loosen the control linkage until speed control gets vague, and the small circlips and snap pins are the first things lost in a teardown. The Control Lever Bracket section lists the bracket, lever, retainer, joint and every clip and pin that holds them together.
Manual Section: Control Lever Bracket p. 35Starter clicks but will not crank
A tired starter usually comes down to worn brushes, a dragging pinion or a failed field coil. The Starting Motor section breaks the starter into its stopper set, pinion, field coil assembly, brushes and bearing assembly so you can rebuild it instead of replacing the whole unit.
Manual Section: Starting Motor p. 37Battery slowly going flat
A charging fault can hide in the brushes, the regulator or the diode assembly, and swapping the whole generator is the expensive way to find out which. The Generator section lists the rotor assembly, stator assembly, brush assembly, regulator, diode assembly and pulley with adjuster individually.
Manual Section: Generator p. 39Dead key switch, good battery
When the starter circuit goes silent, the magnetic relay and its earth cord are prime suspects. The Magnetic Relay section identifies the relay, earth cord and the exact plated bolts and lock nuts that mount them.
Manual Section: Magnetic Relay p. 41Dust getting past the air cleaner
In dry, dusty running the air cleaner element clogs fast, and a collapsed or wrong element lets grit straight into the bores. The Tropics & Desert Type section lists the dust filter, air cleaner assembly, outer element and cleaner body for the hot climate specification.
Manual Section: Tropics & Desert Type p. 43Leaks after reassembly
Reused gaskets and O-rings weep, and finding one missing piece mid reassembly stalls the whole job. The Gasket Set & Tool section lists the complete gasket set along with the cylinder head gasket, O-rings, hydraulic oil pump gasket and suction manifold gasket so you order everything before the head goes back on.
Manual Section: Gasket Set & Tool p. 45Frequently Asked Questions
Which Yanmar engine models does this parts catalog cover?
It covers the 4TN78TL, 4TN78TL(YB401W), 4TNA78TL-DBWVM, 4TNA78TL-RBW and 4TN78TLL-DBWVM. This is Yanmar factory publication Y00B3322, so the part numbers are the ones Yanmar assigned to these exact builds.
Does it list rebuild sizes like undersize bearings and oversize rings?
Yes. The catalog lists a 0.25 US undersize main bearing, a 0.25 US undersize bearing pin, and piston ring sets in 0.25 and 0.5 oversize, each with its own part number, so a crank grind or rebore does not leave you guessing at what to order. p. 16
Does it cover the starter and charging system?
Yes. The Starting Motor section breaks the starter into its pinion, field coil, brush and bearing assemblies, the Generator section lists the rotor, stator, brush assembly, regulator and diode assembly, and the Magnetic Relay section covers the relay and earth cord. p. 37
Is there anything for engines running in hot, dusty conditions?
Yes. The Tropics & Desert Type section lists the parts specific to that specification, including the dust filter, air cleaner assembly, outer element and cleaner body, so you can order the correct element rather than a standard one that does not fit. p. 43
Do I get instant access to this Yanmar 4TN78TL Parts Catalog?
Instant PDF download (1 MB). You get the full 46-page scanned Parts Catalog immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Can I print specific sections of this Yanmar 4TN78TL Parts Catalog?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
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