Mustang ML52 Wheel Loader Service Manual (incl. Wiring)

Check oil level in the hydrostatic circuit first; low oil is the fastest diagnosis. Pull the troubleshooting chart on page 55 and verify the parking brake is fully released, fuses intact, and solenoid valves are energizing. If boost pressure nominal value is not reached, move to page 69: inspect the suction filter for restriction and check the boost pressure valve. Hydraulic oil must stay below 85°C during this test.

Shut down and let it cool before touching anything. Check coolant level and inspect the radiator fins for packed debris. The cooling package on these machines plugs fast in dusty conditions. Clean fins with compressed air from the inside out. Verify the fan motor is spinning at full speed and check the temperature switch and associated fuses per the electrical troubleshooting table on page 123. Thermostat minimum opening distance is 9 mm; a stuck-closed thermostat will cook the engine even with a clean radiator.

Verify hydraulic oil level in the 90-liter tank. Check for visible hose leaks and filter condition before assuming pump wear. Work hydraulics main pressure relief is set at 235 bar; if measured pressure falls significantly short, the relief valve may be leaking or maladjusted. Reference the hydraulic system diagrams starting on page 166 and the schematic on page 185. Tipping load for the 520 loader unit is 3,820 kg; if capacity has dropped noticeably, do a full pressure test before condemning the pump.

Measure battery voltage first: this machine runs a 12 V, 100 Ah battery and a 65 A alternator. Anything below 12.4 V at rest suggests a charging or battery problem. If voltage is good, work through page 122: check the main fuse, confirm the neutral position signal is present, and inspect ignition lock and cabling. If air has entered the fuel system after filter service, bleed it using the procedure on page 28. A clogged fuel filter is a frequent culprit after extended idle periods.

Start with the air filter: a choked filter robs power before anything else and is the cheapest fix. Check the fuel feed system diagram on page 33 and verify the lift pump is delivering clean fuel without restriction. Inspect valve tip clearance if power loss is accompanied by rough idle: inlet clearance is 0.20 mm and outlet is 0.45 mm, checked with the engine cold per the procedure on page 23. Contaminated or stale fuel in the 90-liter tank will produce identical symptoms; drain and refill if the machine sat unused.

Clean and retorque battery terminals before chasing wiring. Inspect the cab-to-frame plug and socket connections at the 21-pole interface, documented on page 143. Pull the fuse chart in the electrical diagrams on page 160 and test each circuit with a multimeter: use Ohm's law to confirm continuity rather than guessing. Corroded connectors at the wiring harness joints are the most common cause of intermittent faults on machines working in mud or standing water. Replace any terminal showing visible green corrosion.