Problems of Piston Rings

Loss of Compression

If the piston rings are not seated properly in their grooves or if they become too worn, they can allow the gas-and-air mixture that burns in the combustion chamber above the piston to leak between the piston and cylinder. When this happens, the engine loses power because the expanding gases can escape --- for example, the car might hesitate when you step on the gas pedal, or it might lose power when you are climbing hills. There will always be a little leakage because no seal can be perfect, but worn rings allow so much leakage (called 'blow-by gases') that engine performance is adversely affected.

Burning Oil

Engine oil forms a thin layer between the piston and cylinder to minimize friction and let the engine work more easily. The piston rings are involved in both spreading oil on the cylinder walls and scraping excess oil off of them. When the rings get too worn, they stop doing their job, and the excess oil is burned during the combustion process. They can also scratch -- or 'score' -- the cylinder walls and allow extra oil to seep into the combustion chamber. Not only does the engine begin burning up oil, the exhaust becomes smoky. In addition, the burnt oil creates excess carbon which deposits itself on the valves, pistons and cylinder walls; this also contributes to the engine's loss of performance.

Overheating

You may not have known that piston rings help control heat buildup in the engine. With so much heat being created during combustion, those thin rings siphon off much of the heat and transfer it to the oil on the cylinder walls. The oil is then scraped off and cycled through the system, giving it a chance to cool, and fresh oil is spread along the cylinder walls to help keep them cooler. If the rings are not doing their job, so much heat can build up that the piston will expand and 'seize up' the engine, or it might just melt. If the rings allow 'blow-by gases,' the hot gases can carry that heat deep into the engine and cause damage in the crankcase; they can also contaminate the oil so it will not do its job.