Kubota GB13 – GB20 problems and faults: causes and solutions
Faults on the Kubota GB13, GB14, GB15, GB16, GB18 and GB20 can almost always be traced back to a handful of classic issues. This guide combines the official troubleshooting table from the Kubota instruction manual with common real-world problems from owners' experiences. Per complaint: symptom, cause and solution.
Suitable for the entire series: Kubota GB13 (D9/DA5/N), GB14 (B9), GB15 (B9/S), GB16 (K/FK/H), GB18 (K/FK) and GB20 (K/FK).
Kubota GB starts poorly or not at all
| Symptom | Likely cause | Solution |
|---|---|---|
| Engine turns over, doesn't start | Fuel not flowing: dirt or water in tank/filter | Drain the tank, replace the fuel filter, clean the glass bowl and O-ring |
| Starts briefly and stalls | Air in the fuel system (after filter change or running the tank empty) | Bleed at the filter and lift pump; check lines, unions and clamps for leaks on the suction side |
| Slower cranking in frost | Oil too thick and/or weakened battery | Winter oil 10W-30, charge the battery; observe pre-glow time (up to 10 s at −15 °C) |
| Glow indicator light doesn't glow | Often not faulty glow plugs but corroded contacts on the glow plug rail, or the glow relay/fuse | Clean the contacts, measure continuity per plug; only then replace the glow plugs |
| Starter motor does nothing | Corroded battery terminals/ground strap, starter safety switch (seat/clutch), ignition switch | Clean and tighten connections, test switches |
From practice: never let the injection pump run dry by running the tank empty — the pump is lubricated by the fuel and will otherwise wear out prematurely. A worn diaphragm in the lift pump causes the same symptoms as a dirty filter; the lift pump for the D905/D1005/D1105 (SKU-56001, € 49.50) is available. Glow plugs for these engines: SKU-55209 (M10 version, € 13.50) — check the thread size of your old plug, as M8 and M10 variants exist.
Kubota GB lacks power, smokes or stalls
| Symptom | Likely cause | Solution |
|---|---|---|
| Loss of power | Fuel shortage or supply issue, clogged air filter | Clean/replace filter(s), check the fuel system for air |
| Black smoke | Poor fuel quality, oil level too high, clogged air filter | Fresh fuel, correct oil level, clean air filter |
| White-blue smoke after starting | Moisture/unburned diesel in the muffler after prolonged idling; otherwise injectors | Warm up under load; avoid prolonged idling; have the injectors tested |
| Sudden stalling | Out of fuel, blocked filter, or air in the system | Refuel, replace the filter, bleed the system; also check the fuel cap vent |
Kubota GB overheats
If the temperature gauge points toward the red zone (coolant ± 125 °C), check in this order: coolant level and leaks, V-belt tension (± 7 mm at 10 kgf — a slack belt is also the cause of a poorly charging battery), and dirt buildup on the grille and radiator screen. From practice, there are two additional deceptive causes: a radiator that looks clean from the outside but is scaled up or clogged internally, and a lower radiator hose that collapses internally while looking fine on the outside. Coolant that keeps being pushed into the overflow tank indicates a leaking head gasket. The water pump (SKU-40905, € 69.50) and thermostat 82 °C (SKU-45101, € 29.50) are both available for the entire series.
Kubota GB electrical problems: battery not charging
If the charge indicator light stays on or the battery keeps running flat, the combination of flywheel alternator + rectifier/regulator is suspect on this generation. Test sequence from practice: measure the alternator's AC voltage at full speed (tens of volts AC = alternator is fine); if no charging voltage then comes out of the regulator, the regulator is faulty. Don't forget the simple causes: rusty ground points and corroded connectors cause identical symptoms. Regulator part numbers differ per version — always verify by serial number.
Kubota GB clutch, lift and axles
Clutch seized: the classic ailment of machines that have been idle for a long time. Pressing the pedal does nothing anymore: the plate is rusted onto the flywheel. Sometimes it can be freed (high gear, brakes locked, start the engine and "jerk" it), otherwise the tractor must be split. New clutch plate GB13–GB15 (SKU-3016014, € 98.50), pressure plate assembly (SKU-75035) and clutch kit GB16–GB20 (VAR-0064, € 174.50) are available from stock. Prevention: store the machine with the pedal pressed in and locked, and regularly drain the clutch housing.
Lift sinks or responds slowly: almost always dirty/old oil, a saturated hydraulic filter or a clogged suction strainer; foaming oil indicates air being drawn in on the suction side. Keep in mind that the lift doesn't sink without an implement attached — that's not a fault. See the hydraulics guide.
Oil leakage at the front axle or PTO: worn seals. For the PTO, first check the shaft stub for wear grooves or burrs and polish them, otherwise the new seal will leak again within no time. Seals for front axle GB13–GB15 (SKU-96036) and stub shaft GB16–GB20 (SKU-96068) are available.
If you can't figure it out, note the serial number and engine code and contact us — the part numbers mentioned are for reference, and you should always verify by serial number, especially with grey imports.
Preventing a fault is cheaper than repairing one
By far most of the complaints above start with old filter material and old oil. An annual service with the filter kit (SKU-10050, € 34.50) and fresh oil prevents nine out of ten faults.
