I. Core Maintenance Philosophy: "Prevention First, Mandatory Maintenance"
Don't wait for a breakdown to repair. Instead, perform mandatory inspections, tightening, lubrication, and replacements based on mileage and time.

II. Daily Maintenance (Pre-trip & Post-trip)
This is the daily work drivers must do to identify potential issues promptly.

• Walk-around Check (360-degree inspection):

  • Exterior: Check for obvious damage, deformation, or cracks on the body, container, and side boards.

  • Lights: Ensure all lights (turn signals, brake lights, marker lights, reverse lights) are working correctly.

  • Tires: Check tire pressure (by tapping with a hammer to listen or using a gauge). Look for abnormal wear, cuts, bulges, and remove stones or debris lodged in the tread.

  • Leak Check: Look under the vehicle for signs of leaking fluids (engine oil, gear oil, brake fluid), air, or water on the ground.

• Key System Checks:

  • Brake System: Listen for air leaks (hissing sound). After starting, check if the air pressure gauge reaches the rated pressure (usually around 8-9 bar) within the specified time. Ensure the low air pressure warning light goes out normally.

  • Suspension System: Check leaf springs for breakage or misalignment. Check air suspension bags for leaks and cracks.

  • Connections: Check the fifth wheel (king pin / coupling plate), locking mechanism for wear and cracks. Inspect electrical and air line connections (7-pin plug, gladhand connectors) for security and integrity.

  • Fasteners: Check key components like wheel nuts/bolts, suspension connection nuts, container hinge bolts for tightness and signs of loosening.

• Post-trip: Clean the vehicle, especially headlights, taillights, and reflective markings to keep them highly visible.

III. Periodic Maintenance (By Mileage or Time)
This is systematic maintenance, best performed by professional mechanics using a lift or inspection pit.

• Monthly / Every 10,000 km

  • Complete Lubrication: Grease all lubrication points including: fifth wheel (king pin), landing gear, suspension system (leaf spring shackles, equalizer beam), etc. This is crucial for reducing wear.

  • Brake System Check: Check brake pad/brake shoe lining thickness. Replace if near wear limit (usually ~5mm remaining). Check brake drums for cracks, heat bluing, or wear grooves. Check brake chamber pushrod travel is within standard range and retracts properly.

  • Tire Maintenance: Rotate tires (recommended every 10-20,000 km) to ensure even wear. Check and correct wheel balance.

  • Tightening Check: Re-torque all wheel nuts to the specified torque using a torque wrench (Very Important!). Check and tighten all chassis bolts, especially U-bolts, torque rod bolts, etc.

• Quarterly / Every 30,000 km

  • Bearing Maintenance: Remove, clean, and lubricate wheel hub bearings. This is core maintenance to prevent "burned up bearings" leading to wheel-off. Replace the grease in the hub. Check bearings for pitting, scoring, wear; replace if damaged. Adjust bearing preload to ensure wheels rotate freely without play.

  • Comprehensive Inspection: Perform a deeper inspection of the frame rails and crossmembers for fatigue cracks. Check if side and rear underrun protection devices are secure and reliable.

• Annual / Every 100,000 km

  • Brake System Deep Maintenance: Replace the desiccant in the air dryer cartridge. Check or replace brake chamber diaphragms, seals in valves (relay valves, ABS valves). Thoroughly drain oil and water mixture from the air reservoirs.

  • Electrical System Check: Inspect all wiring harnesses for wear, aging, broken insulation, and check connectors for corrosion.

  • Body & Paint: Remove rust and touch up paint on corroded areas to prevent further spread.

IV. Key Assembly Specific Maintenance

1. Brake System (Safety Core!)

   • Air Dryer Cartridge: Must be replaced per the maintenance schedule (annually or 100,000 km). Otherwise, moisture will corrode the entire brake system.

   • ABS/EBS System: Periodically read fault codes with a diagnostic tool to ensure proper operation. Keep wheel speed sensors clean.

   • Valves: Investigate and repair relevant valves promptly if air leaks or abnormal braking are noticed.

2. Suspension System

   • Leaf Springs: Check for broken leaves and ensure the center bolt is tight.

   • Air Suspension: Check air bags for cracks, scratches, leaks. Observe if the trailer sags after sitting overnight.

   • Torque Rods / Linkages: Check bushings for cracking, aging, and check ball joints for looseness.

3. Axles & Tires

   • Axles: Maintain proper axle alignment to prevent irregular tire wear.

   • Tires: Use tires of the same size, type, tread pattern, and similar wear. Maintain consistent tire pressure.

4. Electrical System

   • Connectors: Keep the 7-pin socket dry and clean; apply a small amount of petroleum jelly to prevent oxidation.

   • Wiring Harnesses: Secure them properly to avoid chafing against metal parts.

5. Body & Cargo Securement

   • Box Trailer: Check door locks, hinges, and seals.

   • Flatbed / Sided Trailer: Check side board locking mechanisms and hinges.

   • Flatbed/Chassis: Check welds for cracks, focusing on the neck area.

V. Maintenance & Repair Notes

• Use Genuine Parts: Inferior parts, especially for brakes, suspension, and tires, pose significant safety risks.

• Follow Procedures: Tighten fasteners using a torque wrench to the specified torque and sequence (e.g., star pattern). Never use an impact wrench for final tightening without torque verification.

• Keep Records: Maintain detailed maintenance and repair records, noting date, mileage, tasks performed, and parts replaced for tracking and scheduling future maintenance.

• Leave it to Professionals: Have experienced professional technicians perform repairs on safety-critical systems (brakes, suspension, wheel hubs).

In summary: Semi-trailer maintenance emphasizes "frequent inspection, frequent lubrication, frequent tightening." Through daily diligence and regular professional maintenance, you can ensure it remains in optimal condition, operating safely and efficiently to create value.