Gehl 6635SXT Skid Steer Troubleshooting

The Gehl 6635SXT skid steer loader is powered by 187 cu.in (2.9L) Deutz BF4M1011F four-cylinder turbocharged diesel engine with a rated power of 75 hp (56 kW) at 2500 rpm. The Gehl 6635 SXT is equipped with a single-speed or two-speed hydrostatic transmission, radial-lift loader boom, 100H roller chains, and 12x16.5 or 33-15.5x16.5 tires. The hydraulic system has a pump with fluid flow rate of 23 gpm (87.1 lpm). The hydraulic pressure is 3000 psi (207 bar). The skid steer loader has a rated operating capacity of 2350 lbs (1065 kg) and tipping load of 4700 lbs (2130 kg). The max lift height is 122.7" (3120 mm) to hinge pin, and dump height is 93.7" (2380 mm).

Engine Troubleshooting

Engine hard to start or doesn't start

Air in fuel system - Bleed fuel system.
Fuel filter element is clogged - Replace filter element.
Fuel injection nozzles are faulty or clogged - Test injection nozzles and change if necessary.
Water in the fuel system - Change fuel and repair fuel system.
Incorrect valve clearance - Correct valve clearance needs to be set.
Fuel injection pump is defective - Replacement or repair required.

Engine starts and immediately shuts off

Air cleaner is dirty - Install new air cleaner element.
Fuel filter element is dirty - Change filter element.
Fuel injection pump has loose connections - Tighten the connections.
Defective or clogged fuel injectors - Replace fuel injectors.
Damaged fuel injection pump - Replacement or repair required.

Engine shuts off while running

Low coolant temperature - Warm up the engine.
Fuel filter element is dirty - Change filter element.
There is air in the fuel system - Bleed the system.
Clogged or burnt injection nozzle - Test injection nozzles and change if necessary.
Wrong setting of fuel injection pump timing - Adjust fuel injection pump as required.

Engine stalls when idle

Incorrectly set low idle speed - Adjustment required.
Fuel injection pump is not working correctly - Change pump or rebuild it.
Fuel injector fault - Replace or clean fuel injectors.
Valve out of adjustment - Correct valve clearance.

Engine power is insufficient

Plugged air cleaner - Install new air cleaner element.
Fuel injection nozzles fault - Check and replace nozzles if required.
Incorrect fuel injection pressure - Adjust pressure to proper level.
The valve clearance is incorrect - Have it adjusted.
Incorrectly adjusted low idle speed - Correct the settings.
Clogged fuel hoses or lines - Service fuel lines and hoses.
Cylinder head gasket defective - Gasket should be replaced.
Piston rings are worn or damaged - Piston rings replacement required.

Engine overheated

Insufficient coolant fluid - Refill to the correct level and inspect system for leaks.
Not enough engine oil - Checking oil level and add if necessary.
Radiator core is clogged or radiator cap is leaking - Clean radiator or change cap.
Fan belt is broken or worn - If necessary, replace the belt.
Engine is overloaded - Reduce load on the engine.

Insufficient oil pressure

Low crankcase oil level - Check oil level and add oil as required.
Oil filter clogging - Service or change engine oil filter element.
Improper type of engine oil - Fill up with the proper oil viscosity.
Crankshaft bearing oil clearance is excessive - Bearing replacement required.
Defective oil pump - Remove and inspect oil pump.

Abnormal engine noise or knocking

Engine oil level low - Check oil level and add oil as required.
Engine is not preheated - Warm up the engine to required temperature.
Incorrect adjustment of fuel injection pump timing - Set up as recommended.
Too low idle RPM - Adjust the low idle speed.
Fuel injector fault - Clean or replace fuel injectors.
Connecting rod is defective or misaligned - Replace or align connecting rod.
Worn or scored pistons - Replace the pistons.

Drive System Troubleshooting

Machine does not move forward or backward

Insufficient hydraulic oil - Checking hydraulic oil level and add if necessary.
Damaged drive chain - Inspect drive chain and replace defective components.
Faulty input drive shaft - Repair or replace drive shaft.
Relief valve defective or worn - Rebuild or install a new relief valve.
Suction line or hydraulic filter is plugged - Service suction line or change hydraulic filter.
Damaged or worn hand or foot controls - Check and repair as required.
Defective drive pump or motor - Change or repair faulty component.

Low power

Hydraulic oil filter is dirty - Check, clean, or change as necessary.
Relief valve is open or defective - Close or replace relief valve.
Transmission parts are faulty or damaged - Check and change defective components.
Input drive shaft failure - Replace drive shaft.
There is air in the hydraulic system - Air bleeding is required.

Drive system is overheated

Low hydraulic fluid level - Checking hydraulic fluid level and add if necessary.
Hydraulic fluid filter is clogged - Replace hydraulic filter.
Faulty relief valve - Repair or change.
Hydraulic motor or drive pump is worn - Repair or change faulty component.
Dirty oil cooler - Clean cooling fins as required.
Drive system overload - Load should be reduced.

Excessive noise

Incorrect oil viscosity - Use proper oil viscosity.
Air in the hydraulic system - Bleed air from system.
Hydraulic motor or drive pump is defective - Inspect and replace as necessary.
Worn or damaged mechanical components of drive system - Check the parts for defect or damage and change if required.

Hydraulics Troubleshooting

Hydraulic system is overheated

Incorrect hydraulic pressure setting - Adjust pressure correctly.
Unadjusted or defective main relief valve - Adjust or replace the relief valve.
Hydraulic oil is dirty - The oil must be changed.
Lack of hydraulic fluid - Check and refill the hydraulic fluid.
Defective hydraulic pump - Repair or replace pump if necessary.

Lift arm can't drop or lift

Lift controls are damaged - Repair or change.
Hydraulic pump not working - Install new pump or repair it.
Faulty hydraulic control valve - Repair or replace the valve.
Hydraulic cylinder malfunction - Replace or repair boom cylinder.
Insufficient hydraulic oil - Checking hydraulic oil level and add if necessary.

Bucket fails to tilt

Faulty bucket tilt controls - Repair or change.
Hydraulic pump is broken - Repair or install new hydraulic pump.
Hydraulic control valve failure - Repair or replace the valve.
Broken bucket cylinder - Change or repair cylinder.
Low hydraulic oil level - Fill the system to proper hydraulic oil level.

Boom or bucket is working slowly

Faulty hydraulic oil pump - Test the pump performance and change pump if required.
Oil leaks from hydraulic cylinder - Repair leak by replacing the seals.
Low hydraulic oil level - Checking hydraulic oil level and add if necessary.
Defective or not adjusted hydraulic control valve - Repair or adjust properly.
Hydraulic pressure loss - Hydraulic pressure must be set correctly.

Bucket or boom is working jerkily

Air in hydraulic system - Bleed air from hydraulic system.
Dirty hydraulic oil filter element - Change or clean oil filter.
Contaminated hydraulic fluid - The fluid must be changed.
Cylinder tube or rod scoring - Replace failed component.

Hydraulic pump is excessively noisy

Lack of oil or hydraulic leakage - Top up hydraulic oil or remedy leakage in system.
Hydraulic filter is dirty - Replace or clean the filter.
Suction line clogging - Need to service the suction line.
Air trapped in hydraulic pump - Need to bleed air.
Faulty pump components - Rebuild or replace hydraulic pump.

Electrical Troubleshooting

Battery is not charging

Loose or corroded electrical wiring connections - Tighten or service connections.
Defective battery terminal clamps - Change terminal clamps.
Battery failing - Install a new battery.
Defective or loose belt - Need to adjust belt tension or replace belt.

Starter turns slowly

Low battery capacity - Battery is drained, recharge it.
Battery won’t hold charge - Battery needs service or replacement.
Battery terminals are corroded or wires are disconnected - Connect wiring properly or install new terminals.

Starter will not crank

Battery is discharged or worn - Recharge or change battery.
Battery cables are disconnected or incorrectly connected - Check cables and connect as needed.
Battery capacity is low - Recharge the battery.
Starter motor is defective - Change or repair starter.