Car piston rings

How to detect the piston rings failure

The cylinder-piston group inspection is performed in various ways. Measurement of compression inside the cylinders is the most common method. In vehicles with a gasoline engine, you need to unscrew the spark plugs, fill 30-50 ml of oil into each hole and cover them with a dry cloth: it will absorb excess lubricant. Then you have to rotate the engine by 3-4 turns with a starter and measure the compression. If it has raised to 0.9-1.2 mPa, the piston rings are worn out. In diesel engines the lubricant is filled in the same amount, but you need to install the glow plugs back, and then try to start the engine. If at positive ambient temperature and with non-working plugs it has started, then the piston rings are most likely to require replacement.

A more comprehensive inspection can be done at a service station. Typically it is performed using compressed air or vacuum method, it is quite time consuming, but at the same time provides more reliable results.

You may identify that the piston rings need to be examined by the following symptoms:

• loss of engine power;
• increased oil consumption;
• noticeable increase in the fuel consumption, especially at city driving;
• change of exhaust gas color;
• soot deposit on spark plugs;
• oil leakage from under the seals;
• increased pressure of crankcase gases.

Causes of piston ring faults

Piston rings have a limited useful life: 150,000-300,000 km. Neglecting the advised replacement intervals may result in expensive engine repairs.

Piston rings operate in an aggressive environment and are continuously exposed to extremely high temperatures, oil, and exhaust gases. That is why if you install low-quality spare parts, the need to repair the cylinder-piston group can arise sooner than usual.

Premature failure of the piston rings is caused by delayed air filter or oil replacement, its poor quality or non-compliance with the vehicle specifications. Contamination increases the parts abrasive wear, increasing the risk of their warping and fracture. Besides, mechanical damage can occur due to entering of fragments of broken connecting rod, valves, crankshaft into friction pairs.

Damage to the components is frequently caused by usage of low quality fuel. Low octane gasoline causes detonation of the engine. Due to the increase of pressure inside the cylinders, hot gases blow by the piston rings with greater than usual force, destructing them.

Adverse operating conditions, such as short trips, especially in cold seasons, can also reduce the life of the piston rings: the components of the engine not warmed up to operating temperature are insufficiently lubricated, and thus they are highly exposed to abrasion.

The lack of oil in the system leads to the piston jamming and the destruction of its rings. The same faults can result from the power unit overheating.

Many malfunctions of the components occur due to improper installation of them, or as a result of unqualified engine repair, when, after the cylinders boring, an unsuitable piston ring kit was chosen. The lack of the unit surface final polishing may result in accelerated wear of the ring edges, and improperly adjusted clearance of the piston ring locks may lead to the pistons jamming.

Replacement of the piston rings

The piston rings replacement, as well as any other works related to engine repair, has to be performed at a service station, as it will require the engine removal and disassembling, and then precise adjustment of the clearances. It is advised to replace the pistons together with the new components installation, as well as to bore and hone the engine cylinders. Otherwise, the new rings can be destroyed very soon.