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Home / Wheel Loaders / Caterpillar Wheel Loaders / Cat 938K

Caterpillar 938K Troubleshooting

The Cat 938K wheel loader is powered by 402.8 cu.in (6.6L) Caterpillar C6.6 ACERT 6-cylinder turbocharged aftercooled diesel engine with a rated power of 169 hp (126 kW) at 1800 rpm. The Caterpillar 938K is equipped with a 4-range hydrostatic transmission, power steering system, wet disc brakes, and 20.5R25 standard tires. The hydraulic system has a pump with fluid flow rate of 50 gpm (190 lpm). The hydraulic pressure is 4060 psi (280 bar). The wheel loader has a rated operating capacity of 10500 lbs (4765 kg) and tipping load of 21000 lbs (9530 kg). The max lift height is 156.3 inches (3970 mm) to hinge pin, and boom breakout force is 28500 lbs (12955 kg).

Engine Troubleshooting

Engine difficult to start or will not start
Air in fuel system - Bleed fuel system.
Dirty fuel filter - Filter maintenance required.
Fuel injection nozzles are faulty or clogged - Test injection nozzles and change if necessary.
Water or dirt in fuel system - Drain, flush, and service the system.
Valve out of adjustment - Adjust valve clearance.
Damaged fuel injection pump - Replace or rebuild injection pump.

Engine starts but then stops
Air cleaner is dirty - Install new air cleaner element.
Fuel filter element is dirty - Clean the filter or install new filter element.
Fuel injection pump leakage - Check the fuel injection pump for leaks and fix it.
Clogged or defective injectors - Replace or clean fuel injectors.
Fuel injection pump is not operating properly - Replacement or repair required.

Engine stalls while running
Coolant temperature is low - Normalize the temperature by warming up the engine.
Fuel filter element is dirty - Change filter element.
Air trapped in fuel system - Bleed air.
Clogged or defective injection nozzles - Change fuel injection nozzles.
Incorrect adjustment of fuel injection pump timing - Adjust according to specifications.

Engine stops at idle
Incorrect low idle speed adjustment - Correct low idle adjustment.
Fuel injection pump is not operating properly - Replace or rebuild injection pump.
Fuel injector fault - Test and replace fuel injectors if necessary.
Valve clearance is not correct - Adjustment procedure required.

Diesel engine loses power
Plugged air filter - Install new air filter element.
Clogged or burnt injection nozzle - Check and replace nozzles if required.
Fuel injection pressure is wrong - Adjust to correct pressure.
Excessive valve clearance - Correct valve clearance.
Wrong adjustment of low idle speed - Correct low idle adjustment.
Restricted fuel hoses or lines - Clean fuel lines and hoses.
Defective cylinder head gasket - Replace the gasket as required.
Worn or broken piston rings - Install new piston rings.

Engine is overheated
Low coolant level - The cooling system needs to be refilled and checked for faults.
Engine oil level is insufficient - Fill the crankcase with engine oil.
Clogged radiator fins or damaged radiator cap - Clean radiator or install new cap.
Fan belt is worn or faulty - The fan belt needs to be replaced.
Engine is under excessive load - Load reducing required.

Oil pressure too low
Oil level is insufficient - Add oil as required.
Oil filter is clogged - Change or clean engine oil filter element.
Incorrect oil viscosity - Fill up with the correct oil viscosity.
Excessive main bearing oil clearance - Replace bearings.
Defective oil pump - Remove and inspect oil pump.

Engine noises or knocks
Engine oil level is low - Check and refill engine oil.
Engine not warmed up - Normalize the temperature by warming up the engine.
Improper setting of fuel injection pump timing - Check the fuel injection pump timing adjustment.
Wrong adjustment of low idle speed - Need to adjust idle speed.
Dirty or defective injectors - Clean or replace fuel injectors.
Connecting rod is defective or misaligned - Replace or align connecting rod.
Pistons are worn or broken - Pistons need to be replaced.

Hydrostatic Transmission Troubleshooting

Excessive hydrostatic transmission noise
Contaminated transmission fluid or low fluid level - Pour fresh fluid or add transmission fluid to proper level.
Worn or out of adjustment speed control linkage - Replace or adjust linkage.
Relief valve malfunction - Change the valve.
Transmission is under excessive load - Reduce transmission load.
Transmission components are damaged or worn - Check internal transmission parts for damage or wear and replace if required.

Loss of power
Low oil level - Check transmission oil level and add oil as required.
Relief valve is stuck - Install a new valve.
Speed control pedal linkage is bent or not adjusted - Replace or adjust linkage.

Transmission oil overheats
Transmission fluid level is low - Check and refill the transmission fluid.
Transmission fluid filter element clogging - Clean or change transmission fluid filter.
Cooling components are defective or plugged - Inspect all cooling components and replace or clean if necessary.
Transmission overloaded - Reduce the load is required.

Transmission fluid leaks
Broken seals or gaskets - Change defective seal or gaskets.
High internal transmission case pressure - Change defective parts.
Oil drain pipe is plugged - Check pipe and service if necessary.

Hydraulics Troubleshooting

Hydraulic system overheated
Incorrect hydraulic pressure setting - Hydraulic pressure must be set correctly.
Main relief valve failure or improper setting - Adjust the valve or replace if necessary.
Contaminated hydraulic fluid - The fluid must be changed.
Not enough hydraulic fluid in the system - Add fluid to the hydraulic system.
Defective hydraulic pump - Change or repair hydraulic pump if required.

Boom cannot be lowered or raised
Damaged lift controls - Change or repair.
Hydraulic pump not working - Install new pump or repair it.
Hydraulic control valve is defective - Repair or replace hydraulic valve.
Hydraulic cylinder not working - Replace or repair boom cylinder.
Low hydraulic oil level - Checking hydraulic oil level and add if necessary.

Bucket fails to tilt
Bucket tilt controls malfunction - Replace or repair.
Defective hydraulic pump - Replace or repair pump if necessary.
Damaged hydraulic control valve - Repair or replace the valve.
Damaged bucket cylinder - Repair or replace cylinder.
Hydraulic fluid level low - Fill up the hydraulic fluid.

Slow boom or bucket action
Hydraulic pump is faulty - Check the pump capacity and replace pump if required.
Oil leaks from hydraulic cylinder - Correct leakage by changing the seals.
Hydraulic fluid level low - Fill the system to proper hydraulic fluid level.
Hydraulic control valve is not set properly or defective - Adjust properly or repair.
Hydraulic pressure has dropped - Set pressure correctly.

Lift arm or bucket jerks when working
Air in hydraulic system - Need to bleed air.
Plugged hydraulic oil filter - Service or change the hydraulic filter.
Contaminated hydraulic fluid - Hydraulic fluid change required.
Cylinder tube or rod is scored - Replace worn component.

Hydraulic pump makes excessive noise
Low oil level or hydraulic leaks - Refill hydraulic oil or repair leaks in system.
Hydraulic filter clogging - Change or clean oil filter.
Dirty suction line - Clean suction line as required.
Air in hydraulic pump - Bleed air from hydraulics.
Pump components are faulty - Install new hydraulic pump or rebuild it.

Electrical Troubleshooting

Battery does not charge
Corroded or loose cable connections - Service or tighten cable connections.
Battery terminal clamps are defective - Install new terminal clamps.
Worn-out battery - Battery replacement required.
Belt is defective or loose - Belt needs to be adjusted or changed.

Starter turning slow
Battery voltage is low - Battery is drained, recharge it.
Battery is not holding charge - Service charging system or replace battery.
Bad terminals or disconnected battery cables - Connect wires correctly or change terminals.

Starter motor is not working
Battery is discharged or defective - Charge or replace the battery.
Battery cables are disconnected or improperly connected - Inspect cables and connect properly.
Low battery output - Battery is drained, charge it.
Faulty starter motor - Starter needs to be replaced.

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WHEEL LOADERS SPECIFICATIONS

Wheel Loaders, Skid Steers, and Compact Track Loaders