Yanmar AF-15 through AF-18 maintenance schedule: intervals and adjustment values
The maintenance schedule for the Yanmar AF-15, AF-16, AF-17 and AF-18 determines how long this tractor will last — and with proper maintenance, that can be surprisingly long. In this article you'll find all the intervals from the original manual, the important first service after 50 hours, and the exact adjustment values for the V-belt, clutch, brake, steering, and toe-in.
Suitable for the entire series: Yanmar Forte AF-15, AF-16, AF-17 and AF-18, including all versions (Limited, orchard, turf, OK-UFO and EG-UFO). The intervals and adjustment values are the same for all models.
Yanmar AF series: daily checks before work
The manual prescribes a fixed daily routine: tire pressure and wheel bolts, fuel level and leakage, engine oil level (with a cold engine), coolant level, battery fluid, contamination of the air filter and radiator screen, tension of the fan belt, free play of the brake and clutch pedals, steering play, and after starting, the operation of all indicator lights and the color of the exhaust gases. The retractable radiator screen should be cleaned both before and after every workday — a clogged screen is the number one cause of overheating.
Yanmar AF series maintenance schedule by interval
| Interval | Tasks |
|---|---|
| First 50 hours (break-in service) | Change engine oil, change transmission oil, replace engine oil filter and line filter, clean the oil strainer in the transmission housing, re-adjust the new fan belt, retighten bolts and nuts |
| Every 50 hours | Grease all lubrication points (brake pedal shaft, clutch pedal shaft, front axle center pin), clean dust screen and radiator, check fan belt, clean air filter when working in dusty conditions, check electrical wiring and fuel lines |
| Every 100 hours | Change engine oil, clean air filter (normal conditions), check battery acid (specific gravity) and recharge, clean fuel strainer |
| Every 300 hours | Replace engine oil filter, replace transmission oil + line filter, change front axle oil, replace fuel filter element, check transmission oil strainer, have alternator and starter motor checked |
| Every 400 hours | Replace air filter element (when working in dusty conditions; otherwise every 1000 hours and at least once a year) |
| Every 600 hours | Have valve clearance checked, have injectors checked, clean engine housing |
| Annually | Replace coolant (including flushing the radiator internally), replace air filter element, major inspection at dealer or workshop |
| Every 2 years | Replace radiator hoses, fuel lines, power steering high-pressure hose, and weathered wiring — even if the hours haven't been reached |
The manual also applies the following rule: if you don't reach the operating hours, perform the checks at least once a year in any case. Parts with a replacement interval must be replaced every 2 years regardless, irrespective of the hour reading.
Yanmar AF-15 through AF-18 adjustment values
| Adjustment point | Value | Adjustment |
|---|---|---|
| Fan belt (deflection) | 10–15 mm under thumb pressure at the center of the belt | Loosen the alternator bolts and shift the alternator; re-adjust the new belt after 50 hours; only with a cold engine |
| Clutch pedal (free play) | 20–30 mm | Via the turnbuckle in the control rod, then lock it in place |
| Brake pedal (free play) | 25–35 mm, exactly equal on the left and right | Via the turnbuckle behind the pedal; unevenly adjusted brakes will pull the tractor off course |
| Steering wheel (play) | 20–50 mm at the steering wheel rim | Outside this range: have it adjusted by the workshop |
| Front wheel toe-in | 0–5 mm | Loosen the tie rod end lock nuts and adjust the rod length |
| Front wheel bolts | 4.5–5.7 kgm | Check during the daily routine |
| Rear wheel bolts | 11.9–15.1 kgm | Check during the daily routine |
| Tire pressure | Front 1.5 / rear 1.0 kgf/cm² (turf: 1.6 / 1.4) | Maximum 2.0 / 1.6 kgf/cm²; with a front loader, set front tires firmer within the range shown on the tire sidewall |
Yanmar AF series battery and fuses
Check the battery fluid level with every use and only top up with distilled water. Never fast-charge the battery (no quick charger) and always disconnect the negative terminal first when disconnecting. The fuse box contains fuses of 15 A (lighting and horn), 20 A (starting circuit) and 4× 10 A (turn signals, UFO controller, gauges and the external 12V connection), plus spare fuses. There is also a separate main fuse (fusible link) near the engine: if this has blown, the tractor is completely dead — have it checked at the workshop. Always replace a fuse with one of the same rating.
Yanmar AF series lubrication and cooling system
The three lubrication points (brake pedal shaft, clutch pedal shaft, and the front axle center pin) are greased every 50 hours; lubricate immediately after working in mud or water. The cooling system holds 3.6 liters in the radiator and 0.4 liters in the expansion tank. The coolant lasts a maximum of one year; from the factory it is mixed for protection down to −25 °C (45% antifreeze). When changing it, flush the radiator until the water runs clear, and after refilling, let the engine idle for 5 minutes to mix the fluid.
