4 Symptoms of a Bad Piston Ring (& Replacement Cost)

The piston rings ensure that no oil reaches the combustion chamber and keeps the compression in the chamber. Here's how to tell if your piston rings are bad.

piston rings

Pistons rings are something that most people have heard about before but really never seen.

This is mostly because these rings are integrated deeply into all the parts of a car engine.

But what happens if one of these piston rings is going bad? Let’s find out!

This article will explain the common signs of a bad piston ring, function, location, and replacement cost if you need to replace them. First, we will look at the signs:

The most common symptom of bad piston rings is high oil consumption. You will probably notice signs like blue smoke coming from the exhaust during acceleration, and you will probably feel a loss of power in your car.

Because of the piston rings’ vital role, there are some major symptoms you should look out for. Here is a more detailed list of the 4 most common symptoms of bad piston rings.

Bad Piston Ring Symptoms

1. A Large Amount of Oil Disappears 

bad oil consumption

When the piston rings fail, they cannot keep the oil from leaking into the cylinder; as soon as the oil leaks, it will get mixed up in the combustion process.

Slowly and gradually, all your engine oil will leak into the cylinder, and you will witness a drop in your car’s engine oil level. You would need to get an oil refill more frequently.

If you were changing the oil every 5000 miles, you might feel your car needs oil by 3000 miles. If you witness such a phenomenon, you should not waste any time and book an appointment with your auto mechanic. A professional will diagnose the engine’s valve seals and piston rings and advise to replace them if needed

2. Oil leaks

car oil leak

When the piston rings are bad, you will get a high pressure inside of the crankcase. This makes the sealings of the engine to fail and starts leaking oil. If you see many different oil leaks, you should absolutely check the pressure in the crankcase.

You can do this by letting the engine stand on idle and carefully open the oil cap. There should be no pressure at all, but a small vacuum. If the oil cap flies away together with a lot of smoke that pours out – you may have bad piston rings.

3. Weak Acceleration

slow acceleration car

When the piston rings get damaged, the engine’s combustion chamber loses pressure. This causes the engine to lose power since the piston cannot completely compress the fuel and air mixture. As a result, the engine creates less power in each cycle.

You could be slamming the throttle to its limit and still not be feeling your vehicle speed up as it used to before. Loss of acceleration may mean you would have to get your piston rings replaced.

Once you replace the old ones with the new ones, you will get higher compression, and you will feel an immediate change in your vehicle’s power.

4. Blue Smoke Emitting from Exhaust 

oil smoke car e1609805071325

Not only will weared out piston rings cause a loss in performance, but they will also cause your car’s exhaust to emit blue smoke. When the oil gets mixed up with the fuel & air mixture and burns, a thick blue cloud of smoke comes out of the exhaust. This is usually the first symptom you will notice since it is almost immediate.

You should consult a mechanic at the earliest if such a problem presents itself. The longer you ignore the problem, the more advanced it will become. Ultimately, other engine parts will get damaged, leading to a higher repair cost.

Piston Rings Function

piston ring location

The piston rings help keep the combustion chamber known as the area inside each cylinder – pressurized, which makes it easy for combustion to happen. 

The piston rings are the seal between the piston and the cylinder walls to keep the combustion chamber’s pressure and oil in the crankcase. If they deteriorate or fail, your car’s engine will start losing power, and literally, hundreds of other problems may arise if they are not dealt with quickly.

Piston Rings Location

piston ring function

The piston rings are located inside of the engine block, inside the cylinder wrapped around the pistons.

Therefore they are impossible to see without taking the whole engine apart, so to diagnose these, you have to check them with a leak-down-tester or a compression tester.

Piston Rings Replacement Cost

Piston ring replacement cost is between $1000 and $5000, depending on the car model and labor costs. The piston rings cost $40 to $200 depending on how many cylinders your car has. The labor work is between $1000 and $4000.

Piston rings are small, but they are expensive to replace. It basically depends on your car’s make and model, but on average, you could expect to pay from $40 to $200 just for the piston rings. That doesn’t sound much but wait until you add the labor cost to the total.

Since the piston rings are located deep in an engine, the mechanic has to disassemble the engine and reach in to remove the old piston rings and replace them with new ones. This whole process takes time and requires precision.

Once the new piston rings have been put in place, the engine has to be reassembled and fitted back in its position. It would take your mechanic 16 hours or more for the complete job. A certified mechanic will probably do it faster and more likely in the correct way.

To install the piston rings correctly – you have to measure the ring cap and fit them in the right order. You also have to check and measure the cylinder walls for wear before installing the new piston rings. 

You can expect a labor cost between $1000-4000 for a correct piston ring replacement, depending on the engine.

If you know how to replace them yourself, you can do it pretty cheap, though. But be prepared for a big job which you need a lot of knowledge for.

Additionally, you may need to replace other parts while taking the engine apart, and you may even have to redo the engine block.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.