For used tractor units (prime movers for container or semi-trailers), initial basic maintenance directly determines future refurbishment costs and vehicle uptime. Since the previous owner's actual usage history is unknown, it is recommended to follow a "replace-rather-than-inspect" approach for comprehensive servicing.
Key maintenance tasks fall into the following five core areas:
1. Powertrain Maintenance (Top Priority)
Replace engine oil and filter: Regardless of when the previous owner claimed to have changed them, immediately replace them with genuine, heavy-duty oil and filters that meet National VI or National V standards upon acquiring the vehicle.
Replace diesel filters: Both the primary filter (with water-fuel separation) and the secondary filter must be replaced to prevent low-quality diesel from damaging the expensive high-pressure common-rail system.
Inspect and clean the air filter: Check the air filter element; replace it immediately if it is excessively dirty, and clean out any accumulated dust from the intake ducting.
Check coolant: If the freezing point is inadequate or the fluid appears cloudy, perform a complete flush and replacement immediately to prevent engine overheating or cylinder liner cavitation.
2. Chassis and Drivetrain
Replace gear oil: Inspect and replace the gear oil in the transmission and rear axle (differential). These areas are often overlooked in used vehicles; neglect can lead to severe gear damage.
Comprehensive lubrication (greasing): Apply fresh grease to key friction points—such as driveshaft universal joints, leaf spring pins, steering tie-rod ends, and the fifth wheel (coupling)—until the old grease is purged out.
Inspect clutch and brakes: Check the air dryer cartridge (to prevent brake lines from freezing in winter), inspect brake shoe thickness, and check brake actuators for air leaks.
3. Electrical and Air Systems
Check battery status: Used tractor units often suffer from aging batteries with poor charge retention; use a tester to check battery health and replace if necessary.
Troubleshoot dashboard warning lights: Clear historical fault codes and closely monitor warning lights for the engine, ABS, and exhaust after-treatment system.
4. Tires and Steering
Check for abnormal tire wear: Inspect for signs of uneven wear or "tire eating" (misalignment-induced wear). Used tractor units are highly susceptible to uneven tire wear caused by chassis deformation or incorrect wheel alignment.
Perform four-wheel alignment: It is recommended to carry out a full vehicle alignment and adjust the toe-in to ensure the vehicle does not pull to one side or experience uneven tire wear during high-speed driving.
5. Specialized Inspections
Inspect the fifth wheel (tractor coupling): Check the wear on the wear plate and ensure the locking mechanism is not loose; this is critical for safety, as a failure could lead to the trailer detaching.
Inspect the urea system: For China V/VI compliant models, check the urea pump and nozzle for crystallization or blockages.