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Kubota M105S Troubleshooting

The Kubota M105S farm tractor was manufactured from 2005 to 2007. The tractor was designed in 2 versions: M105H (2WD, ROPS) and M105HD (4WD, ROPS). The Kubota M105S is powered by Kubota V3800-DI-TI 4-cylinder direct injection turbocharged diesel engine.

A 230 cubic inches (3.8 L) engine has a cylinder bore of 3.94" (100 mm), piston stroke of 4.72" (120 mm), and rated power of 105 hp (78.3 kW). The Kubota M105S tractor is fitted with 3 types of transmission. Type 1: 16x16 Swing Shift partially synchronized transmission. Type 2: 32x32 Swing Shift Plus Dual Speed partial powershift transmission. Type 3: 24x24 Swing Shift transmission with creeper. Max. forward speed - 21.4 mph (34.5 km/h), max. reverse speed - 21.4 mph (34.5 km/h).

The open center hydraulic system includes a gear pump with a flow rate of 17.2 gpm (65.1 lpm). The hydraulic pressure is 196 bar (2845 psi). The Kubota M105S was equipped with a hydrostatic power steering, hydraulic wet disc brakes, 10.00x16 (2WD) or 13.6x24 (4WD) front tires, and 18.4-34 rear tires. The wheelbase is 95.9 in (2430 mm).

Engine Troubleshooting
Engine will not start or starts up hard
Fuel filter is clogged - Service the filter
Closed fuel cock - Open fuel on-off cock to inject fuel
There is air in the fuel system - Bleed the system
Dirty or faulty injectors - Inspect fuel injectors and replace if necessary
Fuel injection pump is not operating properly - Change or repair the pump
Low engine compression - Check cylinder block and change worn components
Diesel stalls while running
Engine not warmed up - Normalize the temperature by warming up the engine
Air in fuel system - Air-bleed fuel system
Improper fuel injection - Fuel injection settings required
Fuel filter is clogged - Filter maintenance required
Dirty or damaged injectors - Test fuel injectors and change if necessary
Diesel engine stops after starting
Fuel injection pump timing is incorrect - Check and correct settings
Plugged fuel filter - Install new filter element
Fuel injector nozzles fault - Replace fuel injector nozzles
Damaged fuel injection pump - Replace or repair injection pump
Air cleaner element is clogged - Install new cleaner element or replace it
Engine stops while idling
Incorrect low idle speed adjustment - Need to adjust idle speed
Fuel injection pump malfunction - Replacement or repair required
Clogged or defective injector nozzles - Change injector nozzles
The valve clearance is not adjusted - Adjust to proper valve clearance
Engine overheating
Coolant level is low - Fill radiator to proper level. Check radiator and hoses for leaks
Cooling system components are defective or system is clogged - Service the cooling system or change faulty parts
Not enough engine oil - Check and refill engine oil
Incorrect fan belt tension or broken belt - Adjust correctly or install new belt
Defective or wrong type of thermostat - Test thermostat opening temperature, replace as required
Engine lacks power
Dirty or damaged injectors - Service or change fuel injectors
Fuel injection pressure is wrong - Repair or replace injection pump
Air filter element is dirty - Replace filter or install new filter element
Dirty oil filter element - Replace or clean engine oil filter element
Engine overloaded - Load reducing required
Improper valve clearance - Adjust to proper valve clearance
Incorrectly adjusted low idle speed - Adjustment required
Dirt in the fuel pipes or hoses - Clean fuel system hoses and pipes
Engine compression too low: Intake or exhaust valves are damaged - Have valves replaced
Abnormal engine noise or knocking
Fuel injection pump out of timing - Adjust injection timing
Dirty or defective injector nozzles - Service or replace nozzles if required
Low engine oil level - Need to add engine oil
Engine not warmed up - Warm up engine as required
Worn crankshaft or main bearings - Have bearings or crankshaft replaced
Broken or worn piston rings - Replace piston rings
Flywheel bolts are loose - Bolts need to be tightened
High oil consumption
Oil leaks: Gaskets or seals can be faulty - To repair leaks, replace worn parts
Incorrect oil viscosity - Fill up with the correct oil viscosity
Stuck or worn piston rings - Change piston rings
Damaged valve stems or valve guides - Replace the valves
Pistons or cylinder liners are damaged - Check pistons and liners, change as required

Electrical System Troubleshooting
Battery is not charging
Dead cell in battery - Replace the battery
Battery electrical wire harness failure - Inspect wires for defects, change or repair
Loose or corroded battery terminals and cables - Tighten or service cables and terminals
Belt is damaged or belt tension is incorrectly adjusted - Adjust belt tension properly or replace belt
Starter cranks slowly
Battery power is low - Charge the battery
Battery does not hold charge - Service or replace the battery
Bad battery wiring harness - Inspect wiring for malfunctions, replace or repair
Corroded or loose terminals and cables - Clean or tighten cables and terminals
Starter will not crank
Low battery voltage - Recharge the battery
Drained or worn battery - Charge or replace the battery
Damaged starter motor - Change or repair starter
Wiring harness is disconnected or improperly connected - Check wiring harness and reconnect properly

Transmission Troubleshooting
Difficult to shift gears
Clutch is not adjusted or faulty - Adjust or install new clutch
Gear shift linkage is loose or broken - Replace or repair the shift linkage
Worn or damaged shift forks - Shift forks need to be changed
Faulty gear shifting mechanism - Faulty parts must be changed
Low transmission fluid pressure
Insufficient oil supply - Checking transmission oil level and add if necessary
Transmission fluid filter element is dirty (if fitted) - Change or service the transmission fluid filter
Damaged relief valve - Replace the valve
Transmission noises
Broken or worn bearings - Replace faulty bearings
Not enough fluid in transmission - Fill up the transmission fluid
Contaminated transmission fluid - Transmission fluid must be changed
Damaged gears or improper backlash - Set backlash correctly or change the gears
Damaged or worn shift forks - Replace the shift forks
Transmission oil leaking
Gaskets or seals are defective Change defective seal or gaskets
Cracked transmission case - Install a new transmission case

Hydraulics Troubleshooting
Hydraulic system overheating
Improper hydraulic pressure adjustments - Adjust it correctly
Unadjusted or defective main relief valve - Replace or set up the relief valve
Hydraulic fluid contamination - Change hydraulic fluid
Air in hydraulic system - Inspect the suction line, pump seals, and fittings
Low hydraulic fluid pressure
Lack of hydraulic oil - Check oil level and add hydraulic oil as required
Hydraulic fluid filter element is dirty - Change the hydraulic filter element or service if required
Damaged hydraulic oil pump - Test pump flow rate and replace pump if required
Faulty or incorrect setting hydraulic spool valve - Adjust properly or change
Hydraulic cylinder is not working - Check cylinder parts for damage or wear and replace if necessary
Hydraulic piping leaks - Inspect hydraulic system for leaks and repair it
3-point hitch does not raise or raises very slowly
Hydraulic fluid level is insufficient - Check and refill the hydraulic fluid
Cold fluid in hydraulic system - Wait for fluid to warm up
Hydraulic fluid filter element is dirty - Hydraulic filter maintenance required
Hydraulic pump failure - Check pump flow and change pump if necessary
Main relief valve incorrect adjustment or failure - Adjust relief valve or change if required
Defective or not adjusted hydraulic control valve - Change or adjust correctly
Hydraulic cylinder failure - Inspect cylinder parts for wear or damage and replace if required
Suction line is damaged or disconnected - Connect or replace
Hitch won't lower or lowers slowly
Hydraulic spool valve is not set properly or defective - Replace or set properly
Hydraulic cylinder malfunction - Check the hydraulic cylinder parts for damage or wear and replace if necessary
Damaged hitch cross shaft - Replace the shaft
Internal mechanical malfunction with hitch - Replace worn or faulty hitch parts
Three-point hitch raises or lowers not smoothly
Hydraulic system sucks air - Check the pump seals, suction pipe, and fittings
Contaminated hydraulic oil - Change hydraulic oil
Hydraulic pump is defective - Check pump flow and change pump if necessary
Faulty or incorrect setting hydraulic spool valve - Adjust properly or change
Hydraulic cylinder is broken - Inspect the hydraulic cylinder parts for damage or wear and replace if required

Steering System Troubleshooting
Difficult steering
Defective or improperly assembled steering column - Reassemble properly or change steering column
Air in steering system - Bleed air from system
Improper toe-in - Adjust toe-in correctly
Deflated front tyres - Inflate tyres as needed
Faulty steering pump - Check the steering pump and replace if necessary
Damaged or worn hydrostatic steering unit - Repair or change the steering unit
Steering cylinder malfunction - Replace or repair hydraulic steering cylinder
Stuck or worn relief valve - Service or replace the relief valve
Low steering fluid level - Fill the steering system with fluid
Oil leakage in the steering system - Tighten connections of hydraulic hoses and pipes in steering system
Excessive play in steering
Steering column shaft or coupling has maximum wear - Replace faulty component
Hydrostatic steering unit has wear or malfunction - Inspect and change as required
Steering pump not working - Install a new hydraulic steering pump
Steering tie-rod ends or linkage are worn - Change damaged component
Tractor is pulling to left or right
Tires are incorrectly inflated - Inflate as required
Incorrect toe-in adjustment - Check and adjust toe-in
Worn or faulty steering linkage or tie-rod ends - Replace failed component
Defective or worn hydrostatic steering unit - Repair or replace the steering unit
Steering cylinder malfunction - Replace or repair hydraulic steering cylinder
Damaged or improperly adjusted or worn front hub bearings - Adjust properly or replace bearings



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