Piston Rings

Piston Rings

Every internal combustion engine has a specific number of cylinders, which is usually four or six, however, it may also count ten, twelve and even sixteen cylinders. Regardless of their quantity, all engines share a similar design with pistons moving up and down inside cylinders. Each piston features several grooves that go around its circumference and house special spring-loaded metal rings which serve several purposes. 

Piston rings seal pistons inside cylinders to prevent combustion gases from leaking down into the crankcase, which would lead to poor engine performance and increased fuel consumption. They also protect the pistons and cylinder walls from wearing away when the pistons move up and down. Besides, the last ring from the top of each piston scraps oil from the cylinder walls to prevent its burning in the combustion chamber. And last but not least, piston rings transfer the intense heat caused by the combustion process to the cylinder walls, so it can be absorbed by the engine cooling system.

Depending on the function that a piston ring performs, it has one of the following names:

Compression ring

The first and second rings from the top of a piston are called compression rings. As their name indicates, they seal the gap between a piston and the cylinder walls, preventing combustion gases from entering the crankcase. Without compression rings, your vehicle would not move forward since all the power its engine produces would escape from the cylinder.

Oil ring

An oil ring is the last ring from the top of a piston. Its job is to scrape engine oil from cylinder walls when the piston moves down, which prevents oil from burning during the power stroke. At the same time some oil remains on the cylinder walls, which is needed for proper lubrication. 

When should I replace my piston rings?

As a general rule, piston rings are made from softer materials than cylinder walls. This means piston rings are prone to wear and tear over time, which reduces their sealing capabilities. However, piston rings can wear out even faster due to a lack of service and improper maintenance. Here are the most common signs of faulty piston rings:

Increased oil consumption 

It’s natural that all engines consume some oil from one change to another. On the other hand, worn-out or damaged piston rings will allow too much oil to get into the combustion chamber, where it’s then burned along with fuel. If so, this will significantly increase your oil consumption and will cause you to top up its level on a regular basis. Your oil warning light may also come on if the oil level gets too low.

Abnormal smoke from the tailpipe

If you notice blue, gray or white smoke from your exhaust, most likely, your engine burns some oil together with an air/fuel mixture. This happens because of worn-out oil rings which can’t properly scrape oil from the cylinder walls, leaving an excessive oil film on them. Along with abnormal smoke, you’ll notice increased oil consumption.

Loss of power and poor performance

When your compression rings wear out, your engine loses compression and, therefore, its horsepower. The gaps between the cylinder walls and the pistons enlarge, allowing more and more combustion gases pass around pistons into the crankcase, contaminating your oil, which is called “blowby”. As a result, you will experience a lack of overall performance along with poor acceleration and hard engine starts. If you notice this symptom, your engine should be subjected to a compression test as soon as possible. 

Engine overheating

Driving with faulty piston rings for a long time can lead to engine overheating. As a lot of oil gets into the combustion chamber and then is burned with fuel, its level may reduce up to the red zone. The latter is synonymous with a lack of lubrication, increased friction and, therefore, excessive heat buildup in the cylinders. Due to the abnormal temperatures, the pistons and piston rings will quickly expand and begin to scrape the cylinder walls. In the worst case scenario, your piston rings and/or pistons can crack and even get blocked inside the cylinders, causing critical damage to the engine.

Can I drive a car with bad piston rings?

If the only problem caused by your poor piston rings is increased oil consumption, you can drive a car in case of emergency. Otherwise, you should not try your luck in order to save a couple of dollars. You should get in touch with your mechanic and have your vehicle fixed as soon as possible.

Is there any chance to fix bad piston rings?

The good news is that there is very small chance of fixing your engine without expensive repairs and labor. If your piston rings are not worn out, and the symptoms described above were caused by a sludge buildup, you can use one of special high-strength cleaners to clean the rings without having to take your motor apart.

In the event your faulty piston rings are the source of engine problems, the only way to restore your motor to its mint condition is to replace the rings and fix the damage they have caused. In most cases this means engine rebuild or replacement, which involves a lot of labor and a time-consuming repair process. 

Before taking your engine apart, your mechanic will provide a couple of tests to determine what damage to the engine has been already caused. The first one is a compression test, which allows for checking the piston rings for compression leaks past the pistons. The other one is a visual test with a bore score. It is inserted into each spark plug hole to see physical damage caused by bad piston rings.

When both tests confirm that the piston rings are the source of the problem, your mechanic will have to take the engine apart to access damaged areas. Then he or she will be able to calculate the final labor cost and will tell you what replacement parts need to be purchased. Depending on the repair cost, you may go one of the following ways:

If the car is covered under the manufacturer’s warranty and it’s quite new, you’re a lucky person since you’ll not have to pay for your engine rebuild or replacement. 

If your vehicle is not covered under the warranty, but it’s fairly new and you can afford the repair cost, you can restore the car to its original condition.

In case your vehicle has a lot of miles on it and it’s old, the labor along with replacement parts may cost more than the vehicle itself. If so, you should consider purchasing another car. 

Can I fix bad piston rings myself?

Unless you’re an experienced mechanic with sophisticated skills and special tools, you should let a professional do the trick. What you can do is to prevent problems caused by bad piston rings. To make this happen and prolong the service life of your engine, you must follow the manufacturer’s maintenance recommendations found in your owner’s manual. They’re quite simple and do not require special skills or tons of time.