The piston ring is a kind of ring found in combustion engines. Its role is to seal the engine, but also to ensure the smooth running of combustion. The piston ring is mainly found within the engine, but it can also be found in the various pumps or even in the gearbox.
What is a piston ring used for?
The piston ring is a part that ensures the proper functioning of the engine. Indeed, the piston ring is located between the wall of the cylinder and the pistons and ensures the sealing of the latter. The pistons are parts found in the cylinders and whose role is to compress the air/fuel mixture to cause combustion in the engine.
To work well, the pistons must be perfectly sealed, hence the presence of piston rings. They come in the form of an incomplete ring that fits into the groove of the piston. In order to be resistant and waterproof, the piston rings are made of bronze, steel, cast iron or even stainless steel.
Most modern cars are equipped with a 4-stroke engine. There are then 3 piston rings per cylinder: The fire segment: its role is to stop the gases produced during combustion and to cool the piston;
The sealing segment: it is responsible for sealing the combustion and comes in addition to the fire segment. It is also called compression segment;
The scraper segment: as its name suggests, it is used to scrape the oil on the cylinder so that it does not burn. It is also used to prevent the oil from going back into the combustion chamber.
What are the symptoms of a faulty piston ring?
When the piston rings are out of order, the combustion of the engine cannot take place under good conditions. As a result, the entire operation of the engine is disturbed, which can cause serious problems. So, the signs of a malfunctioning piston rings are as follows:
The ignition of the engine light which indicates an engine problem;
Loss of vehicle power due to poor engine combustion;
An increase in engine oil consumption due to a possible leak;
The presence of blue smoke from the exhaust due to burnt oil.
Although piston rings are not wearing parts, they are subjected to high pressure and temperature stresses which can damage them. If in doubt, do not hesitate to have your engine examined by a mechanic.
How to measure a piston ring?
When piston rings are damaged and need to be replaced, they must first be measured in order to install pistons compatible with the vehicle. To correctly take the measurement of the piston rings, you must have a tool called a caliper.
Once you have the caliper, the measurement of the piston rings is done in the following order: Measure the cylinder bore: this is the measurement of the diameter of the pistons. The measurement must be taken perpendicular to the axis of the piston;
Measure the thickness of the piston ring: to measure it, use the caliper;
Observe the shape of the piston ring: depending on the engine, the shape of the piston rings may be different. The segment can be L-shaped, eagle’s beak, rectangular or even semi-trapezoidal.
The difficulty is that the measurement of the piston rings can only be done by passing through the engine block. Thus, if you do not have mechanical knowledge, it is better to entrust the measurement of piston rings to a professional.
The other solution is to consult the vehicle’s maintenance booklet, which lists all the parts compatible with the vehicle and the manufacturer’s recommendations with regard to parts and vehicle maintenance.
What are the risks if a defective piston ring is not replaced?
If the rings are badly worn or broken, this can lead to various consequences. In the best case, only the oil consumption increases. The situation becomes more costly when, due to incomplete combustion of the oil, oil carbon accumulates and settles in the cylinder.
This can ultimately lead to leaking valves, injectors that no longer work properly, and piston rings sticking in the piston grooves. This can damage the cylinder mating surface further reducing engine power, if only due to reduced compression.
In the worst case, there may be a break in the oil film and an increase in friction. This can go so far as to cause what is called friction welding between the piston and the cylinder. The piston and cylinder are then firmly linked in a fraction of a second and the engine stops almost instantly.
This is the classic piston seizure. The repair of the engine is then complex and expensive. An early replacement of defective piston rings is in any case more advantageous.
