Piston rings are important elements of an engine. They serve to maintain compression in the combustion chambers. They ensure dissipation of heat from the pistons to the cylinder sleeve walls, preventing overheating. The piston rings adjust the thickness of the oil film. They are installed with a small gap into special grooves on the outer surface of the piston.

Types

By designation:

• Compression: these rings ensure leak-tightness of the combustion chambers. They are mounted above the oil control rings. They can be flat, twisted or with an L-shaped area, and have tapered edges.
• Oil control: these scrape oil from the cylinder sleeve walls and pistons, leaving an oil film of optimal thickness on their surfaces. They can be one-piece or multi-piece.

By production material:

• Cast iron: these are cheaper, and bed in quickly and easily. They are installed with a new sleeve in order to prevent scoring.
• Steel: these can be stainless steel. Usually, such parts are more expensive, but can withstand higher temperatures. They are suitable for installation in a sleeve with a run-in surface.

An additional coating, molybdenum for instance, can be applied on the surface of piston ringsto improve the operating characteristics and working lifespan.

Operating tips

After replacing piston rings you need to run in the engine in order to let the parts bed in. The procedure is sometimes specified by the car manufacturer in the vehicle technical documentation. In most cases it is performed in several steps. The engine is warmed up to 80°C, then cooled down to 40°C. This step is repeated 8–9 times. Then the engine bay is checked for leaks, and any found are fixed. During the first 1,500 kilometres it’s important to avoid traffic jams, descents and ascents, and keep the engine rotation speed below 2,500 rpm. The first run should be at least 300 kilometres. The rest of the distance can be travelled at intervals convenient for the driver. The oil and oil filter are changed once the run-in is complete.

In addition, it is recommended to use only high-quality oil in order to make piston ringslast. The oil should be of the viscosity recommended by the carmaker. You shouldn’t overload the engine; avoid overheating at all costs. It’s also important to prevent a blown head gasket. If this part is damaged, you need to replace it immediately. Replacing the air filter on time and monitoring the integrity of the intake system can also extend the working lifespan of the parts. If problems have already occurred, engine flushing can be a short-term solution. This is carried out using special products.

Signs of malfunction

Sticking of piston rings is one of the most common defects. This problem lies in immobility of the parts, which leads to leakage in the gap between the piston and the cylinder and ingress of a large amount of oil into the combustion chambers. Sometimes the rings get damaged or burn out, which has the same consequences. There is low compression in the cylinders, and problems starting the engine. Acceleration is slower. Consumption of oil and fuel increases. Blueish smoke comes from the exhaust pipe. A black oily deposits form on the spark plugs.

Causes of malfunction

In most cases sticking of piston rings is caused by the use of oil of an inappropriate viscosity or class, or failure to replace the oil on time. Contaminants getting into the engine due to tearing of the filtering element or a leak in the intake system is also dangerous. Foreign particles in the engine lead to scratching on the surfaces of the parts. Engine overheating, caused, for instance, by malfunctions in the mixture forming process, can lead to burnout of components.

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