Bobcat S850 Skid Steer Troubleshooting

The Bobcat S850 skid steer loader is powered by 230 cu.in (3.8L) Kubota V3800 4-cylinder direct injection turbocharged diesel engine with a rated power of 92 hp (68.6 kW) at 2400 rpm. The Bobcat S850 is equipped with a two-speed hydrostatic transmission, vertical-lift loader boom, 120 HSOC roller chains, and 14x17.5 tires. The hydraulic system has a pump with fluid flow rate of 23 gpm (87.1 lpm) or 36.5 gpm (138.2 lpm). The hydraulic pressure is 3550 psi (245 bar). The skid steer has a rated operating capacity of 3950 lbs (1792 kg) and tipping load of 7900 lbs (3584 kg). The boom lifting force is 6933 lbs (3145 kg), and bucket breakout force is 6975 lbs (3164 kg).

Engine Troubleshooting

Engine starts up hard or won't start

Air trapped in fuel system - Bleed air.
Fuel filter element is clogged - Change filter element.
Clogged or burnt injection nozzle - Clean or change injection nozzles.
Water or dirt in fuel system - Drain, flush, and service the system.
Valve clearance is wrong - Adjust valve clearance.
Fuel injection pump is defective - Repair or change injection pump.

Diesel starts and stalls immediately

Air filter is dirty - Service or replace the air filter.
Fuel filter element is clogged - Change filter element.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Fuel injectors are faulty or clogged - Inspect fuel injectors and change as required.
Fuel injection pump is defective - Change or repair the pump.

Diesel shuts off while driving

Engine is not preheated - Warm up engine as required.
Fuel filter element clogging - Change filter element.
Air in fuel tank - Bleed fuel tank.
Defective or clogged injection nozzle - Clean or replace injection nozzles.
Timing of fuel injection pump is incorrect - Adjust fuel injection pump as required.

Engine stops when idle

Incorrect low idle setting - Adjust the low idle speed.
Fuel injection pump is faulty - Rebuild or change fuel pump.
Fuel injector fault - Clean or replace fuel injectors.
Excessive valve clearance - Adjustment procedure required.

Engine loses power

Air filter is plugged - Clean or change filter.
Clogged or burnt injection nozzle - Inspect nozzles and replace if necessary.
Fuel injection pressure is incorrect - Correct the pressure settings.
The valve clearance is incorrect - Adjust valve clearance according to specifications.
Too low idle RPM - Adjust the low idle speed.
Fuel hoses or lines are dirty - Clean fuel system lines and hoses.
Cylinder head gasket is blown - Gasket should be replaced.
Leaking or damaged piston rings - Piston rings need to be replaced.

Engine overheating

Engine coolant is insufficient - Add coolant and check the components of cooling system.
Lack of engine oil - Add oil to the engine crankcase.
Dirty radiator core or faulty radiator cap - Install new cap or clean radiator.
Excessive wear of the fan belt - Install new fan belt.
Engine is overloaded - Reduce load on the engine.

Oil pressure is insufficient

Lack of oil - Check and refill the oil.
Oil filter element is dirty - Replace or service engine oil filter.
Oil grade or viscosity is wrong - Use oil of correct viscosity.
Crankshaft bearing has excessive oil clearance - Change bearings.
Defective oil pump - Inspect and change as required.

Engine noise or knocking

Low engine oil level - Check and refill engine oil.
Low coolant temperature - Warm up engine as required.
Improper setting of fuel injection pump timing - Use the correct fuel injection pump timing adjustment.
Incorrect low idle speed adjustment - Correct low idle settings.
Damaged or clogged injectors - Replace fuel injectors.
Connecting rod failure or misalignment - Connecting rod needs to be aligned or changed.
Pistons are scored or worn - Replace the pistons.

Drive System Troubleshooting

Drive system doesn't operate in one direction or either direction

Insufficient hydraulic fluid - Add fluid as required.
Drive chain is worn - Inspect drive chain and replace defective parts.
Input drive shaft malfunctioning - Rebuild or change.
Stuck relief valve - Relief valve need to be replaced or repair.
Plugged suction line or hydraulic filter - Clean suction line or change hydraulic filter.
Defective hand or foot controls - Repair or replace.
Worn drive motor or pump - Repair or replace faulty component.

Low power

Dirty hydraulic oil filter - Change hydraulic filter.
Relief valve is damaged or open - Replace or close relief valve.
Worn or faulty transmission components - Inspect and replace faulty parts.
Defective input drive shaft - Replace or service the drive shaft.
Air in hydraulic system - Bleed air from system.

Drive system is overheated

Insufficient hydraulic oil - Fill the system to proper hydraulic oil level.
Hydraulic fluid filter is clogged - Check, clean, or change as necessary.
Defective relief valve - Repair or install a new relief valve.
Drive pump or hydraulic motor is damaged - Repair or replace faulty component.
Plugged hydraulic oil cooler - Cooling fins need to be cleaned.
Drive system overloaded continuously - Reduce drive system load.

Excessive noise

Improper oil viscosity - Use the specified type of oil.
Hydraulic system is leaking air - Air bleeding is required.
Worn hydraulic motor or drive pump - Inspect and replace as necessary.
Mechanical parts of drive system are damaged or worn - Check the components for worn or defect and replace if necessary.

Hydraulics Troubleshooting

Hydraulic system has overheating

Hydraulic pressure is not correct - Adjust it correctly.
Main relief valve failure or improper setting - Adjust or change relief valve.
Hydraulic oil contamination - Hydraulic oil change required.
Not enough hydraulic oil in the system - Fill the hydraulic system with oil.
Defective hydraulic pump - Replace or repair pump if necessary.

Boom fails to lift or drop

Damaged lift controls - Replace or repair.
Hydraulic pump malfunction - Repair or change pump if required.
Hydraulic control valve is defective - Repair or change hydraulic valve.
Hydraulic cylinder malfunction - Replace or repair boom cylinder.
Hydraulic oil is insufficient - Fill the system to proper hydraulic oil level.

Bucket is not working

Bucket controls failure - Replace or repair.
Hydraulic pump failure - Change or repair hydraulic pump if required.
Hydraulic control valve failure - Repair or change hydraulic valve.
Bucket cylinder malfunction - Change or repair cylinder.
Low hydraulic oil level - Fill the system to proper hydraulic oil level.

Slow boom or bucket operation

Worn hydraulic oil pump - Check pump capacity and change if necessary.
Leaking hydraulic cylinder - Cylinder seals need to be replaced.
Low hydraulic oil level - Checking hydraulic oil level and add if necessary.
Defective or not adjusted hydraulic control valve - Set properly or repair.
Hydraulic pressure has dropped - Correct adjustment is required.

Bucket or boom is moving jerkily

Air in the hydraulic system - Need to bleed air.
Clogged hydraulic oil filter element - Service or change the hydraulic filter.
Hydraulic fluid is contaminated - Fill up with fresh hydraulic fluid.
Scored cylinder tube or rod - Replace failed component.

Hydraulic pump is excessively noisy

Hydraulic leaks or low oil level - Remedy hydraulic leakage or refill oil as necessary.
Hydraulic filter is clogged - Replace or clean the filter.
Plugged suction line - Service the suction line.
Air trapped in hydraulic pump - Remove air from hydraulics.
Pump parts are worn out - Change or rebuild pump.

Electrical Troubleshooting

Battery won’t charge

Corroded or loose cable connections - Service or tighten connections.
Electrical terminal connectors are defective - Replace terminal connectors.
Battery is defective - Change the battery.
Damaged or loose belt - Change belt or adjust belt tension.

Starter motor cranks slow

Battery capacity is low - Recharge the battery.
Battery drains quickly - Battery needs to be serviced or replaced.
Disconnected wires or corroded battery terminals - Connect wiring correctly or install new terminals.

Starter will not crank

Battery is discharged or worn - Charge or change the battery.
Wiring harness is disconnected or improperly connected - Check wiring harness and connect as required.
Battery voltage is low - Charge the battery.
Defective starter motor - Repair or change starter.