The piston rings have three functions: they isolate the combustion chamber from the crankcase, limit the engine oil consumption and remove the heat generated in the combustion process. There are three types of piston engine rings: sealing rings, scrapper rings and scrapper-compression rings. They are fitted in grooves located on the inner side of the piston surface. Their failure results mainly from wear or cracking. If this is the case, the cylinder compression ability deteriorates, the engine wear accelerates and the fuel consumption increases.
What are piston rings?
Piston rings seal the engine pistons inside the cylinders. They are shaped like metal rings and placed in special grooves on the outer surface of each piston.
There are three types of piston rings. Sealing rings, also referred to as compression rings, are fitted closer to the piston bottom. They seal the combustion chamber and prevent it from being penetrated by spent gases. Sealing / scrapper rings are fitted under the compression rings. They are responsible for the further sealing of the combustion chamber and for preventing oil from being sucked out of the crankcase and into the combustion chamber during a combustion stroke. Scrapper rings are fitted below the other two ring types. Their task is to scrape the oil film off of the cylinder walls as the piston moves downward. They have special grooves allowing them to drip the excess oil scraped off of the cylinder walls back into the sump.
When should piston rings be replaced?
A piston ring failure results in deteriorated compression and too much oil being used by the engine. In extreme cases, pistons may bend and, consequently, wear faster, causing a specific noise at the idle speed.
How are piston rings replaced?
Replacing piston rings requires removing the pistons. To this effect, the cylinder head must be removed from the engine block, followed by the sump. After unscrewing the connecting rod ends, the pistons and the connecting rods can be removed from the top through the cylinder openings.
When fitting new rings, have the pistons inspected and ensure that each piston ring is properly locked. Fitting the pistons equipped with new rings in the cylinders requires using a special tool called the piston ring compressor. When screwing the connecting rod to the crankshaft you should have the pans located there inspected.
What else to keep in mind?
A new gasket must be used when fitting the head. In addition, the engine oil, filter and timing belt should be replaced."