Product Technology

Why Do Car Engines Suffer from Cylinder Scoring? Veteran Mechanics Reveal Major Causes

Posted on by Daisy
18
Nov

What Does “Cylinder Scoring” Mean?

“Cylinder Scoring” is damage caused by friction between the piston and the cylinder wall, resulting in scuffs or scratches on the cylinder wall. This phenomenon is usually caused by poor lubrication, overheating, or foreign objects inside the engine.

Five major signs of engine “Cylinder Scoring” symptoms?

  • During a routine maintenance session, only the piston rings for the first and third cylinders were replaced. A few days later, the engine exhibited reduced power compared to its performance before the maintenance, accompanied by increased oil consumption.
  • Engine Noise: Cylinder Scoring leads to increased friction between the piston and cylinder wall, which can cause metal scraping or knocking sounds. These noises are usually more noticeable during cold starts or at high RPMs.
  • Due to damage to the cylinder wall, piston movement becomes obstructed, leading to a drop in the compression ratio. This results in significantly reduced engine output, manifesting as poor acceleration and difficulty climbing slopes.
  • Cylinder scuffing compromises the sealing of the cylinder wall, allowing oil to leak into the combustion chamber. This results in incomplete combustion and abnormal exhaust emissions, such as:Blue Smoke: Oil burning in the combustion chamber.Black Smoke: Incomplete combustion of the air-fuel mixture.White Smoke: Coolant entering the combustion chamber.
  • Preliminary Inspection of Four Sets of Pistons and Cylinder Liners: The top of the pistons shows severe burn marks. The first and second piston rings have seized in their grooves. Metallic residues from the burned pistons have adhered to the cylinder wall at the top dead center of the cylinder. The cylinder wall displays severe blue scuff marks. No abnormalities are observed in the other pistons and cylinder liners.

What causes an engine suffer from it ?

  • Engine Oil Failure:

    Using counterfeit engine oil during maintenance or neglecting regular maintenance can lead to oil failure. Since engine lubrication and sealing entirely rely on oil, a lack of proper lubrication will result in damage to the camshaft, piston rings, and cylinders.

  • High Engine Temperature:

    Particularly in older vehicles, poor engine cooling can cause high temperatures, leading to piston expansion. As the piston expands, the clearance between the piston and cylinder narrows, eventually causing the piston to seize in the cylinder, resulting in scuffing. If the engine’s high-temperature warning light turns on, it is crucial to stop and inspect the vehicle. Regularly replacing coolant and cleaning the radiator can help prevent this issue.

  • Frequent Engine Knocking or Detonation:

    Engine knocking or detonation refers to abnormal combustion inside the engine. During detonation, the cylinder operates chaotically, with energy colliding and the cylinder swaying side to side, producing knocking sounds. Over time, this can lead to cylinder scuffing.

  • Prolonged High-Speed Engine Operation:

    High-speed operation, such as running the engine at 5000 RPM or higher, can pose a scuffing risk if the oil viscosity is low, the oil film is too thin, or the increased RPM leads to a rise in engine temperature. Insufficient lubrication under these conditions can result in cylinder damage.

  • Severe Engine Lugging:

    Engine lugging occurs when the gear is too high, and the engine’s current power output is insufficient to drive the vehicle. This situation causes the engine to shake violently, increases noise levels, and can lead to damage to the cylinder walls.

  • Foreign Objects Entering the Cylinder:

    Since the clearance between the piston and cylinder wall is minimal, any foreign object entering the cylinder can become lodged between the piston and cylinder wall, scratching and damaging the cylinder wall.

  • Carbon Buildup on the Piston Rings:

    The piston rings seal the piston and cyHigh Engine Temperaturelinder wall. During engine operation, the piston rings directly contact the cylinder wall and create friction. Under normal circumstances, piston rings and pistons are relatively independent and can move freely. Severe carbon buildup on the piston rings can cause them to seize and lose their ability to self-adjust, leading to cylinder wall damage.

  • Oil Film Breakdown on Cylinder Walls:

    During normal engine operation, a continuous lubricating oil film forms on the cylinder walls to reduce friction and prevent direct contact between the piston rings, pistons, and cylinder walls. If this oil film breaks down, direct metal-to-metal contact occurs, causing severe wear and scuffing of the cylinder wall.

Do I have to replace the engine if it is “Cylinder Scoring” ?

Cylinder scuffing doesn’t always require a full engine replacement. Depending on the severity of the damage, different repair methods can be applied. Here are the common approaches to repairing cylinder scuffing:

Minor Cylinder Scuffing: Surface Repair

If the scuffing is minor and only involves superficial scratches on the cylinder wall, the following methods may suffice:

  1. Polishing
    Use specialized tools (e.g., cylinder honing machines) to smooth out the scratches and restore the cylinder wall’s surface.
  2. Replacing Piston Rings
    If the scuffing has worn down the piston rings, replacing them and adjusting the gaps can resolve the issue.
  3. Using Repair Agents
    In cases of light scuffing, adding metal repair agents (e.g., cylinder wall restorers) can help improve micro-level wear.

Moderate Cylinder Scuffing: Boring + Oversized Pistons

For more severe damage where the cylinder wall is heavily scratched but structurally intact, boring the cylinder is a common solution:

  1. Boring
    Use a cylinder boring machine to enlarge the cylinder diameter and remove the damaged surface.
  2. Oversized Pistons
    Install oversized pistons and piston rings that match the new cylinder dimensions.
  3. Additional Adjustments
    Inspect related components such as connecting rods and crankshafts to ensure proper coordination.

Severe Cylinder Scuffing: Cylinder Liner Repair

If the cylinder wall damage is beyond direct repair, the following methods are available:

  1. Cylinder Liner Installation
    Bore out the damaged cylinder wall and insert a durable liner (cylinder sleeve) to restore the cylinder’s dimensions.
  2. Replacing Related Components
    After installing the liner, replace pistons, rings, and other parts to ensure compatibility.

Irreparable Damage: Engine Replacement

In the following scenarios, replacing the entire engine assembly may be the most economical and reliable choice:

  1. Multiple Cylinders Scuffed
    When multiple cylinders are severely damaged, the repair cost can be too high.
  2. Cylinder Wall Cracked
    If the cylinder wall is completely broken, repair is risky and impractical.
  3. Engine Nearing End of Life
    If the engine is old and scuffing is just one of many issues, replacing the engine may be more cost-effective.

How to avoid and maintain it?

1. During vehicle maintenance, it is important to choose engine oil with a viscosity appropriate for the current seasonal temperature. For example, in northeastern regions, can use 15W-40 oil in summer, while 10W-30 oil in winter. The lower viscosity oil offers good low-temperature fluidity, ensuring proper lubrication for the engine.

2. In daily driving, always refuel with high-quality diesel from reputable gas stations to avoid inferior diesel. Additionally, regularly replace the diesel filter and ensure you purchase genuine filters. Make sure to regularly drain water from the system to provide the engine with clean diesel. If the fuel injectors are affected, seek professional repairs from authorized service centers.

3. Inspect the engine’s air intake system for proper operation, especially on vehicles equipped with intercoolers. Check whether the intercooler radiator is clogged with debris, which could reduce its cooling efficiency. If the clogging is severe, disassemble and clean the intercooler to restore its cooling capacity and lower the engine’s intake temperature.

Symptoms of engine cylinder scuffing: how many does your car have? After reading this article, we hope you can clearly assess your vehicle’s condition. Timely maintenance and part replacement can help prevent more serious issues from developing.

You may also want to know.

How to Remove Carbon Deposits from Your Engine?

Choosing The Right Engine Oil For Your Car

Daisy

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