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Bobcat T66 Troubleshooting

The Bobcat T66 compact track loader driveline system components: a 146.5 cu.in (2.4L) Bobcat Doosan D24 4-cylinder turbo diesel engine with a rated power of 74 hp (55.2 kW), and 1-speed or 2-speed hydrostatic transmission. The hydraulic system has a pump with a rated flow of 17.6 gpm (66.5 lpm). The system pressure is 3550 psi (245 bar). The Bobcat T66 is equipped with a vertical-lift loader boom, solid-mounted or torsion suspension undercarriage, and rubber tracks. The loader 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 2450 lbs (1110 kg), and tipping load is 7000 lbs (3175 kg).

Engine Troubleshooting

Engine starts up hard or won't start
Air trapped in fuel system - Bleed air.
Fuel filter plugging - Change filter element.
Fuel injection nozzles are clogged or faulty - Install a new kit of correctly balanced nozzles.
Water in the fuel system - Change fuel and repair fuel system.
Valve out of adjustment - Correct valve clearance.
Faulty fuel injection pump - Install a new pump or rebuild.

Engine stalls after starting
Air filter is dirty - Service or replace the air filter.
Fuel filter plugged - Clean or change the filter.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Fuel injectors are dirty or defective - Change or clean fuel injectors.
Fuel injection pump malfunctioning - Repair or replace injection pump.

Engine stalls after running
Low coolant temperature - Normalize the temperature by warming up the engine.
Fuel filter element is dirty - Change the filter element.
Air trapped in fuel system - Bleed air.
Fuel injection nozzles are damaged or dirty - Clean or replace injection nozzles.
Fuel injection pump timing is wrong - Adjust as recommended.

Engine stalls at low idle speed
Incorrect low idle speed adjustment - Need to adjust idle speed.
Damaged fuel injection pump - Install a new fuel pump or repair.
Defective fuel injectors - Replace fuel injectors.
Improper valve clearance - Need to adjust valve clearance.

Loss of engine power
Dirty air cleaner - Clean or replace element.
Fuel injection nozzles are faulty or clogged - Check and replace nozzles if required.
Incorrect fuel injection pressure - Check the fuel injection pressure and adjust if necessary.
Excessive valve clearance - Check and adjust as required.
Wrong adjustment of low idle speed - Correct the settings.
Dirt in the fuel lines or hoses - Fuel hoses and lines must be clean.
Damaged cylinder-head gasket - Replace the gasket as required.
Damaged or leaking piston rings - Piston rings replacement required.

Engine overheats
Coolant level is low - Add coolant and check the components of cooling system.
Low engine oil level - Fill up the oil to required level.
Defective radiator cap or clogged radiator core - Install new cap or clean radiator.
Fan belt is broken or worn - Belt change is required.
Engine overload - Reduce engine load.

Oil pressure is low
Oil level is insufficient - Add oil as required.
Plugged engine oil filter - Service or change engine oil filter element.
Incorrect engine oil Use proper viscosity oil.
Excessive main bearing oil clearance - Change bearings.
Oil pump is damaged - Repair or replace.

Engine noise or knocking
Engine oil level low - Checking oil level and add if necessary.
Low coolant temperature - Warm up the engine.
Fuel injection pump timing is not adjusted - Adjust according to specifications.
Incorrect low idle setting - Adjust the low idle speed.
Fuel injector fault - Replace fuel injectors.
Connecting rod is defective or not aligned - Align or change connecting rod.
Pistons are worn or broken - Have pistons replaced.

Drive System Troubleshooting

Drive system doesn't work in either direction
Low hydraulic oil level - Check and refill the hydraulic oil.
Damaged or jammed undercarriage tracks - Repair or remove jamming.
Faulty relief valve - Repair or change.
Hydraulic filter or suction line is clogged - Clean suction line or replace hydraulic filter.
Faulty hand or foot controls - Repair or change.
Damaged drive pump or motor - Inspect and change as required.

Machine will not move straight or moves jerkily
Damaged or jammed undercarriage tracks - Repair or remedy jamming.
Worn or loose tracks - Adjust track tension properly or repair tracks.
Debris, dirt, or foreign objects stuck in undercarriage track frame - Clean undercarriage track frame, remove foreign objects and debris.

Loss of power
Hydraulic oil filter is dirty - Replace or clean hydraulic filter.
Relief valve is damaged or open - Change or close relief valve.
Transmission parts are worn or defective - Inspect and replace defective parts.
Defective input drive shaft - Repair or install a new drive shaft.
Air leaks in hydraulic system - Bleed air from hydraulic system.

Drive system overheating
Low hydraulic fluid level - Checking hydraulic fluid level and add if necessary.
Hydraulic fluid filter is dirty - Change or clean hydraulic filter.
Relief valve failure - Rebuild or install a new relief valve.
Hydraulic motor or drive pump is defective - Inspect and replace as necessary.
Clogged hydraulic oil cooler - Cooling fins need to be cleaned.
Drive system is overloaded - Reduce loading.

Excessive noise
Oil viscosity is incorrect - Drain and refill with proper oil.
Air in hydraulic system - Need to bleed air.
Worn hydraulic motor or drive pump - Inspect and replace as necessary.
Worn or defective mechanical components of drive system - Inspect the components for defect or damage and repair as needed.

Hydraulics Troubleshooting

Hydraulic system has overheating
Hydraulic pressure is incorrect - Adjust it correctly.
Misadjusted or defective main relief valve - Adjust or replace the relief valve.
Hydraulic oil is dirty - Change hydraulic oil.
Lack of hydraulic oil - Add oil to the hydraulic system.
Defective hydraulic pump - Change or repair hydraulic pump if required.

Boom does not raise or lower
Damaged lift controls - Change or repair.
Damaged hydraulic oil pump - Repair or change pump if required.
Hydraulic control valve is defective - Repair or change hydraulic valve.
Hydraulic cylinder not working - Repair or change hydraulic cylinder.
Insufficient hydraulic fluid - Add fluid as required.

Bucket won't move
Faulty bucket tilt controls - Check and repair as required.
Defective hydraulic pump - Repair or install new hydraulic pump.
Defective hydraulic control valve - Replace or repair the valve.
Hydraulic bucket cylinder is defective - Replace or repair cylinder.
Insufficient hydraulic fluid - Add fluid as required.

Slow boom or bucket operation
Hydraulic pump is defective - Check pump capacity and change if necessary.
Leaking hydraulic cylinder - Repair leak by replacing the seals.
Insufficient hydraulic fluid - Fill up the hydraulic fluid.
Hydraulic control valve is defective or set improper - Adjust properly or repair.
Hydraulic pressure is low - Set pressure correctly.

Bucket or boom movements are jerky
Air in hydraulic system - Air bleeding is required.
Dirty hydraulic oil filter element - Clean or change the filter.
Hydraulic fluid contamination - Hydraulic fluid change required.
Cylinder rod or tube is scuffed - Replace damaged component.

Excessive hydraulic pump noise
Hydraulic leakage or lack of oil - Add hydraulic oil or correct system leaks.
Plugged hydraulic filter - Service or change hydraulic filter.
Plugged suction line - Need to service the suction line.
Pump is sucking air - Air bleeding is required.
Faulty pump components - Rebuild or change hydraulic pump.

Electrical Troubleshooting

Battery will not charge
Electrical cable connections are loose or corroded - Tighten or clean connections.
Defective battery terminal clamps - Replace terminal clamps.
Battery failing - Change the battery.
Loose or defective belt - Adjust belt tension or change the belt.

Starter turns slowly
Low battery power - Charge the battery.
Battery is not holding charge - Service charging system or change battery.
Bad battery terminals or disconnected wiring - Check cable connections and replace or service terminals.

Starter is not cranking
Battery is low or faulty - Change or recharge battery.
Wiring is incorrectly connected or disconnected - Inspect wiring and connect correctly.
Low battery voltage - Recharge the battery.
Defective starter motor - Repair or change starter.