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Bobcat S66 Troubleshooting

The Bobcat S66 skid steer loader driveline system components: a 146.5 cu.in (2.4L) Bobcat Doosan D24 4-cylinder turbocharged diesel engine with a rated power of 74 hp (55.2 kW), and 2-speed hydrostatic transmission. The hydraulic system has a pump with a rated capacity of 17.6 gal/min (66.5 l/min). The system relief pressure is 3500 psi (241 bar). The Bobcat S66 is equipped with a vertical-lift loader boom, 120 HSOC roller chains, and 10x16.5 or 31-12x16.5 tires. The skid steer has a max lift height of 120" (3050 mm) to hinge pin and dump height of 94.3" (2395 mm). The rated operating capacity is 2400 lbs (1090 kg), and tipping load is 4800 lbs (2180 kg).

Engine Troubleshooting

Engine starts up hard or won't start
There is air in the fuel system - Bleed the system.
Fuel filter element clogging - Filter maintenance required.
Fuel injection nozzles are faulty or clogged - Replace injection nozzles.
Water in the fuel system - Change fuel and repair fuel system.
The valve clearance is incorrect - Have it adjusted.
Fuel injection pump malfunctioning - Repair or replace injection pump.

Engine starts but immediately stalls
Air filter is plugged - Service or replace the air filter.
Fuel filter element is dirty - Replace the filter element.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Fuel injectors are dirty or defective - Test and replace fuel injectors if necessary.
Fuel injection pump is not operating properly - Repair or replace injection pump.

Engine stops suddenly during operation
Engine not warmed up - Warm up engine as required.
Fuel filter plugging - Change filter element.
Air in fuel tank - Bleed fuel tank.
Fuel injection nozzles are faulty or clogged - Replace injection nozzles.
Improper setting of fuel injection pump timing - Use the correct fuel injection pump timing adjustment.

Engine stops when idle
Wrong adjustment of low idle speed - Adjust low idle speed.
Fuel injection pump is damaged - Repair or install a new fuel pump.
Fuel injector fault - Clean fuel injectors or change it.
Excessive valve clearance - Correct valve clearance needs to be set.

Engine power is too low
Plugged air cleaner - Clean or change cleaner.
Defective or clogged injection nozzle - Test injection nozzles and change if necessary.
Improper fuel injection pressure - Adjust to proper pressure.
Valve out of adjustment - Adjust valve clearance according to specifications.
Wrong adjustment of low idle speed - Adjust low idle speed.
Fuel hoses or lines clogging - Clean fuel hoses and lines.
Cylinder head gasket is worn - Change cylinder head gasket.
Damaged or leaking piston rings - Install new piston rings.

Engine overheating
Low coolant level - The cooling system needs to be refilled and checked for faults.
Engine oil level is low - Need to add engine oil.
Radiator fins are clogged or radiator cap is faulty - Change cap or clean radiator.
Fan belt is loose or defective - Replace as required.
Engine is under excessive load - Reduce load on the engine.

Low oil pressure
Not enough oil in the engine - Fill up the engine oil.
Clogged oil filter element - Service or change engine oil filter element.
Oil grade or viscosity is wrong - Use correct viscosity oil.
Incorrect oil clearance in main bearing - Bearing needs to be changed.
Worn oil pump - Repair or change.

Engine noises or knocks
Lack of engine oil - Fill up the oil to required level.
Engine is cold - Engine is not warmed up to required temperature.
Timing of fuel injection pump is incorrect - Adjust fuel injection pump as required.
Low idle speed adjustment is incorrect - Need to adjust idle speed.
Fuel injectors are dirty or defective - Replace fuel injectors.
Connecting rod is defective or misaligned - Connecting rod must be aligned or replaced.
Pistons are worn or broken - Replace the pistons.

Drive System Troubleshooting

Machine is not moving forward or backward
Insufficient hydraulic fluid - Add fluid as required.
Worn drive chain - Inspect drive chain and replace faulty parts.
Input drive shaft is defective - Repair or replace drive shaft.
Relief valve worn or defective - Rebuild or install a new relief valve.
Suction line or hydraulic filter is clogged - Clean suction line or change hydraulic filter.
Worn or defective hand or foot controls - Change or repair.
Defective drive pump or motor - Inspect and change as required.

Power is too low
Plugged hydraulic oil filter - Change or service hydraulic filter.
Relief valve is worn or opened - Change or close relief valve.
Transmission components are faulty or damaged - Check and change defective components.
Worn input drive shaft - Repair or replace faulty drive shaft.
There is air in the hydraulic system - Bleed air from system.

Drive system keeps overheating
Hydraulic fluid level low - Fill the system to proper hydraulic fluid level.
Clogged hydraulic fluid filter - Replace hydraulic filter.
Stuck relief valve - Service or change relief valve.
Worn hydraulic motor or drive pump - Repair or replace faulty component.
Clogged hydraulic oil cooler - Clean the cooling fins.
Overloaded drive system - Reduce the load.

Drive system is noisy
Oil viscosity is too heavy - Use the specified type of oil.
Air in hydraulic system - Air bleeding is required.
Drive pump or hydraulic motor is damaged - Inspect and change as required.
Worn or defective mechanical parts of drive system - Inspect the parts for worn or defect and repair as needed.

Hydraulics Troubleshooting

Hydraulic system overheats
Hydraulic pressure is not adjusted correctly - Set pressure correctly.
Unadjusted or defective main relief valve - Replace or set up the relief valve.
Hydraulic oil contamination - Change hydraulic oil.
Hydraulic fluid level is insufficient - Need to add fluid.
Faulty hydraulic oil pump - Repair or install new hydraulic pump.

Lift arm cannot be raised or lowered
Lift controls are damaged - Repair or change.
Hydraulic pump malfunction - Repair or replace pump if necessary.
Hydraulic control valve failure - Repair or change hydraulic valve.
Hydraulic cylinder is broken - Install a new boom cylinder or repair it.
Hydraulic fluid level low - Fill up the hydraulic fluid.

Bucket won't move
Bucket controls are faulty - Repair or change.
Damaged hydraulic oil pump - Repair or change pump if required.
Hydraulic control valve malfunction - Repair or change hydraulic valve.
Hydraulic bucket cylinder not working - Replace or repair cylinder.
Hydraulic fluid is insufficient - Fill the system to proper hydraulic fluid level.

Boom or bucket runs slowly
Hydraulic pump is faulty - Check the pump performance and replace it if required.
Leaking hydraulic cylinder - Cylinder seals need to be replaced.
Insufficient hydraulic fluid - Add fluid as required.
Defective or not adjusted hydraulic control valve - Repair or set properly.
Hydraulic pressure loss - Correct setting is required.

Lift arm or bucket movements are jerky
There is air in the hydraulic system - Air bleeding is required.
Hydraulic oil filter clogging - Clean or install new filter.
Hydraulic oil contamination - Change hydraulic oil.
Cylinder rod or tube is scuffed - Change worn component.

Hydraulic pump makes excessive noise
Hydraulic leaks or low oil level - Remedy hydraulic leakage or refill oil as necessary.
Plugged hydraulic filter - Clean or replace the filter.
Suction line is clogged - Suction line needs to be cleaned.
Air enters the pump - Need to bleed air.
Pump parts are worn out - Replace or rebuild the pump.

Electrical Troubleshooting

Battery will not charge
Corroded or loose cable connections - Clean or tighten wiring connections.
Defective electrical terminal connectors - Change terminal connectors.
Battery is worn - Battery replacement required.
Belt is damaged or loose - Belt needs to be adjusted or replaced.

Starter cranks slow
Battery power is low - Battery needs to be recharged.
Battery won’t hold charge - Service charging system or change battery.
Battery terminals are corroded or wires are disconnected - Check cables and clean or change terminals.

Starter motor is not working
Battery is drained or defective - Change or recharge battery.
Wiring is improperly connected or disconnected - Check wiring and connect properly.
Low battery output voltage - Recharge the battery.
Damaged starter motor - Starter needs to be changed.