The diesel engine, as the core powertrain of commercial vehicles, features a compact structure and excellent power performance. However, its reliable operation is highly dependent on standardized maintenance and care. The following details the key points of professional maintenance, based on Euro VI emission technology requirements and original manufacturer service specifications, to help extend engine life and ensure the stability of power output.
Routine Maintenance for Diesel Engines
Daily Basic Inspection (Before Each Startup / After Shutdown)
Fluid System Inspection
Check that the engine oil level is between the upper and lower marks on the dipstick.
Use Weichai dedicated CJ-4 grade or higher oil, ensuring oil pressure is within the range of 100-250 kPa at idle and 350-550 kPa at rated operating conditions.
Coolant must be a long-life antifreeze type, with the level maintained between the marks on the expansion tank.
Check coolant lines for leaks to prevent abnormal water temperature due to water pump impeller corrosion or thermostat sticking.
Fuel System Check
Verify the tightness of fuel lines. Use diesel fuel compliant with Euro VI standards and allow it to settle and be filtered for 72 hours.
Check that the fuel filter has no clogging alarm, and that the low-pressure fuel circuit pressure is not less than 4 bar to prevent common rail system abnormalities due to insufficient fuel supply.
Intake and Electrical System Check
Clean the air filter dust cup. Replace the filter element promptly if the clogging indicator light illuminates; operation without an air filter is strictly prohibited.
Check intake pipes for looseness or air leaks, and ensure the intercooler fins are not blocked by debris.
Verify battery voltage and the tightness of wiring harness connections. Ensure the crankshaft position sensor gap is within the standard range of 0.8-1.5 mm.
Periodic Tiered Maintenance (Based on Operating Hours / Mileage)
Minor Service (Every 500 hours / 50,000 km)
Replace engine oil and oil filter, and clean the fuel filter element simultaneously. Check drive belt tension for any aging or cracking.
For the SCR aftertreatment system, clean the urea tank and filter, and top up with legitimate diesel exhaust fluid (DEF).
Avoid private mixing, which can reduce catalytic efficiency.
Major Service (Every 2,000 hours / 100,000 km)
In addition to minor service items, focus on valve clearance adjustment: adjust to (0.40±0.06) mm for intake valves and (0.60±0.06) mm for exhaust valves when cold.
Adjust EVB clearance to (0.40±0.06) mm. Adjust by barring the engine twice following the firing order (1-5-3-6-2-4).
Tighten lock nuts strictly to a torque of 45±5 N·m. Calibrate fuel injector leak-off quantity; replace any injector with a single leak-off rate exceeding 150 ml/min.
Use the original manufacturer calibration equipment for injector pressure calibration.
In-depth Maintenance (Every 3,000 hours / 150,000 km)
Clean carbon deposits from the EGR cooler and intake manifold using processes like walnut shell blasting to remove deposits.
Inspect turbocharger rotor shaft axial and radial clearance, ensuring no abnormal noise, and avoid disassembling or impacting precision components.
Check DPF regeneration status to prevent frequent regeneration caused by prolonged low-speed, high-load operation.
Key System-Specific Maintenance
Valvetrain Maintenance
Periodically check the contact condition between the four-valve mechanism’s valve bridges and adjustment screws.
Use dedicated feeler gauges (0.40mm, 0.60mm) during adjustment to ensure clearance precision, preventing power loss due to poor valve sealing.
Aftertreatment System Maintenance
Regularly clean the DOC catalyst and DPF. Read exhaust backpressure data via a diagnostic tool; perform high-temperature regeneration or professional cleaning if abnormally high.
Check the urea pump operation status to prevent filter clogging from affecting injection accuracy.
Electronic Control System Protection
Unauthorized disassembly of precision components such as the ECU and common rail pump is strictly prohibited.
Repairs must be performed by authorized Weichai service stations.
Use dedicated diagnostic tools to read key data streams like rail pressure and boost pressure, and promptly troubleshoot fault codes such as P2263.
Special Operating Conditions and Prohibitions
After a cold start, idle the engine for 3-5 minutes. Do not start moving until oil pressure exceeds 150 kPa and coolant temperature exceeds 60°C. After high-load operation, run at low speed for 5-10 minutes before shutdown to protect the turbocharger bearing lubrication.
Prohibit revving the engine in neutral and prolonged idling (not exceeding 3 minutes) to avoid DPF regeneration abnormalities. In winter, when the environment is below 0°C and no antifreeze is used, drain the coolant to prevent the engine block from freezing and cracking.
During repairs, use only Weichai genuine parts. Connecting rod bolts are one-time-use components and must be replaced after disassembly. Main bearing bolts must be tightened according to the specified torque and angle procedures.