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Home / Wheel Loaders / Caterpillar Wheel Loaders / Cat 938M

Caterpillar 938M Troubleshooting

The Caterpillar 938M wheel loader is powered by 427.7 cu.in (7.1L) Caterpillar C7.1 ACERT 6-cylinder turbocharged diesel engine with a rated power of 182 hp (136 kW) at 1800 rpm. The Cat 938M is equipped with a hydrostatic transmission, power steering system, hydraulic 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 11075 lbs (5025 kg) and tipping load of 22150 lbs (10050 kg). The max lift height is 156.3 inches (3970 mm) to hinge pin, and boom breakout force is 29035 lbs (13170 kg).

Engine Troubleshooting

Engine starts hard or doesn't start
Air in the fuel pipes - Bleed the fuel pipes.
Fuel filter plugged - Change filter element.
Fuel injection nozzles are dirty or defective - If necessary, replace with a new nozzle.
Water or dirt in fuel system - Drain, flush, and service the system.
Valve clearance is out of adjustment - Have it adjusted.
Fuel injection pump damage - Change or repair the pump.

Diesel starts but immediately shuts off
Air filter is dirty - Service or replace the air filter.
Fuel filter plugged - Change or clean the filter element.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Defective or clogged fuel injectors - Replace fuel injectors.
Fuel injection pump is damaged - Rebuild or install a new injection pump.

Engine stalls after running
Engine is cold - Warm up to required temperature.
Fuel filter element is clogged - Install new filter element.
Air in fuel system - Bleed fuel system.
Fuel injection nozzles are damaged - Clean or replace injection nozzles.
Fuel injection pump timing is wrong - Adjust as recommended.

Engine stalls when idle
Low idle speed setting is incorrect - Need to adjust idle speed.
Fuel injection pump is defective - Change or repair the pump.
Damaged or clogged injectors - Inspect fuel injectors and change as required.
Valve out of adjustment - Correct valve clearance needs to be set.

Engine power is too low
Clogged air filter - Replace or clean air filter element.
Fuel injection nozzles are faulty or clogged - Clean or replace injection nozzles.
Uneven fuel injection pressure - Adjust to proper pressure.
Incorrect valve clearance - Adjust valve clearance.
Low idle speed setting is incorrect - Adjust the low idle speed.
Fuel lines or hoses are dirty - Service fuel lines and hoses.
Cylinder-head gasket is broken - Cylinder-head gasket replacement required.
Piston rings are broken or leaking - Change piston rings.

Engine is overheated
Lack of engine coolant - The cooling system needs to be refilled and checked for faults.
Lack of engine oil - Check and refill engine oil.
Clogged radiator fins or leaking radiator cap - Clean radiator or replace cap.
Fan belt is broken or worn - If necessary, replace the belt.
Diesel engine overloaded - Load reducing required.

Oil pressure is insufficient
Engine oil insufficient - Fill up the engine oil.
Oil filter element is dirty - Change or clean engine oil filter element.
Oil grade or viscosity is wrong - Drain crankcase and refill with correct oil.
Crankshaft bearing oil clearance is incorrect - Replace bearings.
Worn oil pump - Check and replace if necessary.

Engine noise or knocking
Lack of engine oil - Fill the crankcase with engine oil.
Engine is not warmed up to required temperature - Warm up the engine.
Fuel injection pump timing is not adjusted - Adjust the pump as required.
Incorrectly adjusted low idle speed - Correct the settings.
Clogged or defective injectors - Replace or clean fuel injectors.
Connecting rod is defective or not aligned - Need to change or align the connecting rod.
Worn or broken pistons - Pistons need to be replaced.

Hydrostatic Transmission Troubleshooting

HST transmission noise
Dirty transmission fluid or insufficient fluid level - Pour fresh fluid or add transmission fluid to proper level.
Worn or unadjusted speed control linkage - Adjust or repair linkage.
Relief valve is stuck - Replace relief valve as required.
Excessive transmission load - Reduce the load is required.
Worn or defective transmission components - Change or repair defective parts.

Power is insufficient
Low fluid level - Add fluid to the transmission housing.
Relief valve is stuck - Change the valve.
Speed control pedal linkage is damaged or out of adjustment - Repair or adjust linkage.

Transmission oil overheating
Insufficient transmission fluid - Checking transmission fluid level and add if necessary.
Plugged transmission oil filter - Service or replace the transmission oil filter.
Cooling components are plugged or defective - Check all cooling components and clean or replace if required.
Transmission overload - Reduce transmission load.

Transmission oil leakage
Broken seals or gaskets - Install new gaskets or seal.
Internal transmission housing pressure is too high - Repair or replace damaged components.
Oil return tube is plugged - Clean or replace the tube.

Hydraulics Troubleshooting

Hydraulic system has overheating
Hydraulic pressure is not correct - Correct adjustment is required.
Misadjusted or defective main relief valve - Set up or change the relief valve.
Hydraulic oil is dirty - The oil must be changed.
Hydraulic oil level is low - Fill up the hydraulic oil.
Hydraulic pump is faulty - Change or repair hydraulic pump if required.

Lift arm won't raise or lower
Faulty lift controls - Repair or change.
Hydraulic pump malfunction - Replace or repair pump if necessary.
Hydraulic control valve is faulty - Repair or replace the valve.
Hydraulic cylinder is defective - Install a new boom cylinder or repair it.
Insufficient hydraulic fluid - Add fluid as required.

Bucket tilt does not work
Bucket tilt controls malfunction - Repair or change.
Hydraulic pump is broken - Repair or replace pump if necessary.
Hydraulic control valve is defective - Repair or change hydraulic valve.
Hydraulic bucket cylinder not working - Repair or replace cylinder.
Low hydraulic oil level - Check and refill the hydraulic oil.

Boom or bucket runs slowly
Defective hydraulic pump - Flow-rate pump and change pump if necessary.
Leaking hydraulic cylinder - Cylinder seals need to be replaced.
Hydraulic oil level low - Check and refill the hydraulic oil.
Hydraulic control valve is unadjusted or worn - Set correctly or repair.
Hydraulic pressure loss - Correct adjustment is required.

Bucket or boom is jerky
Hydraulic system is leaking air - Air bleeding is required.
Hydraulic oil filter clogging - Clean or replace the filter.
Dirty hydraulic oil - Hydraulic oil change required.
Scored cylinder tube or rod - Change worn component.

Hydraulic pump is noisy
Insufficient oil level or leaking hydraulic system - Add hydraulic oil or correct system leaks.
Dirty hydraulic filter - Service or change hydraulic filter.
Suction line is dirty - Clean suction line as required.
Pump is sucking air - Air bleeding is required.
Pump parts are worn out - Replace or rebuild the pump.

Electrical Troubleshooting

Battery is not charging
Electrical cable connections are corroded or loose - Tighten or service connections.
Faulty battery terminal clamps - Replace terminal clamps.
Battery is worn - Battery replacement required.
Belt is worn or loose - Belt needs to be adjusted or replaced.

Starter turns slowly
Low battery voltage - Battery needs to be recharged.
Battery is not holding charge - Service battery or change it.
Disconnected battery cables or bad terminals - Connect cables correctly or replace terminals.

Starter will not crank
Battery is low or faulty - Change or recharge battery.
Disconnected or incorrectly connected wires - Inspect battery wires and connect correctly.
Low battery power - Battery needs to be recharged.
Starter motor failure - Starter should be changed.

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WHEEL LOADERS SPECIFICATIONS

Wheel Loaders, Skid Steers, and Compact Track Loaders