What do you think of the engine of a used car?
When buying a used car, the status of the engine is a key factor in determining the performance and life of the vehicle. How to judge whether the engine of a used car is healthy? This article will provide you with a detailed guide from multiple dimensions such as appearance inspection, start-up testing, operation status, and maintenance records.
1. Engine appearance inspection
First, open the hood and observe the appearance of the engine. Here are some key checkpoints:
| Check items | Normal performance | Abnormal performance |
|---|---|---|
| Oil color | Transparent or light yellow | Black or milky white (coolant may be mixed) |
| Engine cabin cleanliness | No obvious oil stains or dust accumulation | Apparent oil stains and heavy dust |
| Belt status | No cracks, moderate tension | Prominent cracks, loose or too tight |
| Screws and seals | No disassembly marks, good seal | The screw has signs of twisting, and the sealant is overflowing |
2. Engine start test
When starting the engine, pay attention to the following behavior:
| Test items | Normal performance | Abnormal performance |
|---|---|---|
| Startup time | Start smoothly within 3 seconds | Startup delay or multiple attempts |
| Start the sound | Stable, no noise | Sharp noise or metal impact |
| Idle stability | The speed is stable at 600-900 rpm | The speed fluctuates greatly or suddenly stops |
3. Engine operation status check
The performance of the engine during operation can better reflect its health:
| Check items | Normal performance | Abnormal performance |
|---|---|---|
| Exhaust color | Colorless or light white (cold days) | Blue (burn oil) or black (inadequate burning) |
| Power Response | Accurate throttle, smooth acceleration | Inability to accelerate or feel strong in abruptcy |
| Engine vibration | Slight vibration without abnormal shaking | Violent jitter or intermittent vibration |
| Water temperature | Stay at around 90°C | Too high or heat up too fast |
4. Verification of maintenance and maintenance records
Through maintenance records, you can understand the historical status of the engine:
| Record Type | Ideal | Beware of the situation |
|---|---|---|
| Oil replacement frequency | Every 5000-10000 km or 6 months | Too long intervals or missing records |
| Overhaul record | No or reasonable instructions (such as timing belt replacement) | Engine cylinder opening or replacement of core components |
| Fault code history | None or resolved small issues | The same fault code frequently occurs |
5. Professional testing suggestions
For ordinary buyers, the following professional means can be used to further verify the engine status:
1.OBD Diagnostic Device Reads Fault Code: Connect to the OBD interface of the vehicle and check whether there are hidden fault codes.
2.Cylinder pressure test: The pressure of each cylinder should be measured through professional equipment, and the difference should not exceed 10%.
3.Engine oil analysis: Take samples and inspect, which can detect the content of metal debris and judge the internal wear.
4.Lift inspection: Check whether there are any oil leakage marks on the chassis, especially the junction of the crankshaft oil seal and the transmission.
Summarize
When purchasing a used car, the engine inspection requires a multi-faceted judgment of the appearance, operating status and historical records. It is recommended to give priority to maintaining vehicles with complete records and conduct professional inspections before transactions. Remember that a healthy engine should start quickly, run smoothly, respond sensitively, and have no abnormal noise or vibration. With the above methods, you can greatly reduce the risk of purchasing a problem engine.
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