Step 1: Engine operating condition inspection
The engine is the core component of a truck and also the most valuable part of a used truck. A good engine can run hundreds of thousands of kilometers, while a faulty engine may face major repairs as soon as you buy it. When checking the engine, it is best to start it when the vehicle is completely cooled down, and it is recommended to inspect the car in the morning. Normal startup should be crisp and clear, without any abnormal noise. After startup, the idle speed should be smooth, and the sound should be low and even. If there are difficulties in starting, metal impact sounds, or abnormal knocking sounds, extra attention should be paid.
It is also important to observe the smoke emitted from the exhaust pipe after idling the vehicle for five to ten minutes. A small amount of light white smoke belongs to normal water vapor, especially common in winter. But if thick white smoke is emitted, it indicates that the coolant may have entered the cylinder, which is a sign of cylinder gasket damage. Blue smoke emitted indicates burning of engine oil, usually caused by worn piston rings or aging valve seals. If black smoke is emitted, it indicates insufficient combustion, which may be related to the fuel injector or turbocharger. The issues of blue smoke and thick white smoke are quite serious and require careful consideration.
In addition, you can also check the turbocharger by removing the intake pipe and manually moving the turbine blades. If the blades rotate flexibly without obvious shaking, it indicates normal operation. If the blades are stuck or the axial clearance is too large, it indicates that the turbine has worn out, and the replacement cost is between 5000 and 15000 yuan. At the same time, it is necessary to inspect the appearance of the engine, check whether there are cracks or oil leakage marks on the cylinder block, and whether there are signs of screw tightening, which can help determine whether the engine has undergone major repairs. It is also worth checking whether the coolant is turbid. If there is engine oil entering, it indicates that the cylinder gasket has been damaged.
Step 2: Chassis and frame inspection
The chassis is the skeleton of a truck, and once the main beam deforms or cracks, the vehicle is basically useless. Many accident cars have been repaired well in appearance, but the chassis damage is difficult to fully recover. When inspecting the beam, stand in front of the front of the car and observe whether the beam is on the same straight line. The problem can usually be seen with the naked eye. Carefully inspect the surface of the main beam for any welding repair marks. The paint surface of the area that was re welded after the accident fracture will have significant differences from other areas. Whether the rivet is loose is also important, as it indicates that the vehicle has been subjected to severe impact. If there are wrinkles or dents on the main beam, it is structural damage and it is not recommended to purchase such a car.
The suspension system also needs to be carefully inspected. Whether the steel plate spring is broken or misaligned, and whether the gap between each piece is uniform. Is the saddle bolt loose and is the nut severely worn. The balance shaft can be pulled up and down to feel the wheel hub. If the gap is obvious, it indicates a problem. Regarding the axle, check for cracks and oil leakage marks on the axle housing. If you hear a buzzing sound while driving, it indicates that the gears have been worn. The flipping mechanism of the cab cannot be ignored. Whether the hydraulic lift pump leaks oil and whether the flipping locking mechanism is flexible and reliable are related to the convenience and safety of daily use.
Step 3: Verification of driving mileage and maintenance records
The numbers on the odometer can only be used as a reference, and odometer tuning is not uncommon in the second-hand truck industry. But through some details, you can determine the actual usage intensity of this car. The degree of wear on the leather of the steering wheel is a good reference indicator. The steering wheel at 100000 kilometers has only slight wear, while the steering wheel at 300000 kilometers or more will have obvious patina or even wear. The dust cover of the gear lever is also the same. It is basically intact after 100000 kilometers, but may be damaged after 300000 kilometers. The rubber on the clutch pedal and brake pedal, as well as the seat cushion, can help you determine the actual strength of use. If the instrument display shows only 80000 kilometers, but the steering wheel and gear lever are clearly worn, it can be basically confirmed that the gauge has been adjusted.
It is also important to request the seller to provide the original maintenance manual, check if the service station’s stamped records are continuous, and pay attention to whether the repair items in the records are reasonable. Some high-end car models’ on-board computers will record the total working hours of the engine, and you can ask the repair shop to read the ECU data. Multiplying the engine working hours by the average speed, long-distance transportation is generally calculated at 50 to 60 kilometers per hour to obtain the approximate actual mileage. The color of the inner wall of the exhaust pipe can also indicate a problem. Normal carbon deposits in gray black indicate a reasonable mileage, while burnt black and greasy indicate a high mileage or oil burning. If it is too clean and has been cleaned clearly, it may be suspicious and may be a cover up for the problem.
Step 4: Tire and Brake System Evaluation
Tires and brakes are the safety guarantee of trucks, directly related to driving safety. The cost of replacing a complete set of tires and brake pads on the car ranges from 20000 to 40000 yuan, which cannot be ignored when purchasing the car. When checking tires, the wear of tires on the same axle should be basically consistent. If one side of the tire is unevenly worn, it indicates that there is a problem with wheel alignment or axle deformation. Severe wear in the middle of the tread indicates excessive long-term inflation pressure, while severe wear on both sides of the tread indicates insufficient long-term inflation pressure.
The production date of the tire is also worth checking. There is a series of codes starting with DOT on the tire wall, with the last four digits representing the production date, such as 3522 indicating the 35th week of 2022. Tires with rubber over five years old will age, and it is recommended to replace them even if the tread is deep. If the production dates of all tires on the vehicle are inconsistent, it indicates that they were pieced together later. It is also necessary to check whether there are bulges on the sidewall, which means that the internal curtain is broken and may cause a tire blowout at any time. This is a safety hazard that cannot be ignored.
In terms of the braking system, the thickness of the brake pads should be observed from the gap between the wheel hubs, and any remaining thickness less than three millimeters needs to be replaced immediately. Check if the brake pads are unevenly worn, which indicates a problem with the brake cylinder or adjustment arm. Check for cracks and obvious grooves on the surface of the brake drum. If the groove depth exceeds 1.5 millimeters, the drum needs to be bored or replaced. Also, check all air and oil pipes for air and oil leaks, open the drain valve of the air storage cylinder, and check if there is a large amount of accumulated water or oil inside. If there is, it indicates that the air dryer has failed.
Step 5: Identification skills for accident vehicles
The biggest risk of an accident car is that there may still be structural hazards after repair, and once a secondary accident occurs, the safety performance will be significantly reduced. When inspecting the A-pillar and B-pillar of the cab, the original welding points should have uniform circular indentations. If the welding points are irregular or have polishing marks, it indicates that they have been cut and repaired before. Comparing the gaps on the left and right sides, the gap between the car door and the body should be basically the same on both sides, and the gap between the hood and the front panel should be uniform and symmetrical.
Checking the glass production date is also a practical method. The corners of the windshield and door glass have production date markings, usually a combination of numbers and dots. If the date of a certain piece of glass is significantly later than the vehicle’s manufacturing date, it indicates that the location has been damaged and replaced. The date of manufacture of the vehicle can be checked from the nameplate on the driver’s door frame or passenger seat. In terms of checking the car paint, a paint film gauge can be used to measure the thickness of each part of the paint surface. The original factory paint is generally between 80 and 120 microns. Visually inspecting adjacent panels for color differences, checking for paint residue on the window seals and lamp edges, are all clues to determine whether to repaint.
The interior of the cab should also be carefully inspected. Lift up the carpet to check for rust or mud at the bottom, which can help eliminate waterlogged vehicles. Pull out all seat belts and check for water stains and mold on the bottom. Whether there is rust inside the cigarette lighter holder often reflects the true experience of the vehicle.
