What Does Cylinder Scoring Mean?
4 Answers
Cylinder scoring refers to the formation of deep grooves on the inner wall of the cylinder, causing the piston, piston rings, and cylinder wall to lose their sealing ability during friction. This results in reduced cylinder compression pressure and loss of power, making it one of the common faults in automotive engines. The following are the causes of cylinder scoring: 1. The clearance between the piston and cylinder is too small. 2. The fit between the cylinder sleeve outer diameter and the bore is either too tight or too loose; the cylinder sleeve quality does not meet requirements; or the cylinder sleeve hardness is too low, leading to piston scoring. 3. The piston itself does not meet quality requirements, or the piston pin and piston pin bore assembly are too tight, causing axial deformation of the piston, resulting in the piston skirt roundness not meeting specifications. 4. During assembly, the piston and cylinder were not thoroughly cleaned, leaving sand particles trapped in the piston or its ring grooves, or the intake passages were not cleaned properly. 5. The air filter is faulty or was not installed during testing. 6. The lubricating oil is of poor quality, contains excessive impurities, or does not meet the required specifications. 7. The piston rings are broken or the piston ring end gap is too small.
Cylinder scoring means there's a problem inside the engine, where the piston scratches the cylinder wall during movement. Sounds scary, right? There are many causes, the most common being insufficient lubrication, delayed oil changes with degraded oil, or engine overheating. The symptoms are quite obvious too - the car makes strange creaking noises when driving, has noticeably weaker acceleration, and fuel consumption is significantly higher than usual. In severe cases, the engine may even smoke or stall. I've experienced this firsthand - a friend's car used cheap low-grade oil to save money, resulting in cylinder scoring repairs costing tens of thousands. So don't be careless when driving, especially check the oil and cooling system before long trips. Maintaining normal operating temperature can effectively prevent this trouble.
To prevent cylinder scuffing, engine oil is key and must be changed on schedule. It is recommended to use full synthetic oil to protect the engine. When the engine operates at high temperatures, it is prone to insufficient lubrication, increasing friction between the cylinder walls and pistons, leading to scuffing. Develop the habit of regularly checking the coolant level, avoid continuous long-distance driving in summer, and let the car rest for a while after parking. If you notice abnormal engine noises or a drop in power, visit a repair shop immediately. Having driven multiple cars, I know that repairing cylinder scuffing requires engine disassembly for cleaning or part replacement, which is costly. Routine maintenance, such as checking the oil condition every 5,000 kilometers, can reduce the risk.
On a technical level, cylinder scoring refers to scratches on the cylinder wall caused by piston friction, often due to oil film breakdown or contamination. Smooth cylinder walls are crucial for engine operation; once damaged, power output becomes unbalanced, resulting in vibrations and noise. Repairs are labor-intensive, typically requiring engine disassembly to measure scratch depth—light cases may need polishing, while severe ones require cylinder boring or sleeve replacement. Repair costs vary by model, starting from several thousand for ordinary cars. Although modern electronically controlled engines are advanced, mechanical wear issues still rely on quality oil maintenance and regular air filter changes to prevent foreign objects from entering the cylinders.
