bad piston rings

Piston Ring Symptoms & Replacement Cost

In Engine by Magnus Sellén1 Comment

piston rings symptomsAn engine is a complex machine. It contains a lot of small components which need to be in the perfect working condition for you to enjoy the full power of the engine.

One such part is the piston ring.

The piston rings help keep the combustion chamber –also 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 pressure in the combustion chamber, 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.

The piston ring is a small component and pretty cheap to buy – But when it comes to replacement cost, you have to take apart the whole engine and it can become very costly.

Signs of bad Piston Rings

bad piston ringsThe piston rings have a very important job to separate the combusted exhaust to not entering the crankcase and mixing with the engine oil. A small amount of combustion will always go through the piston rings into the crankcase – that’s why you have crankcase ventilation to vent out these gases out from the engine.

If the piston rings are bad, too much combustion will go through the piston rings down to the crankcase – and the crankcase ventilation may not be enough to pour these gases out.

This will create a high pressure inside of the engine which will push out oil from all engine sealings. 

Therefore, you should always consult a mechanic as soon as you see any or all of the symptoms mentioned below. Here are the major symptoms that arise when piston rings fail.

1. A Large Amount of Oil Disappears 

When the piston rings are failing they are not able to keep the oil from leaking through into the cylinder. As soon as the oil leaks through 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 levels. 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 inspect the engine’s valve seals and piston rings and advise to replace them if needed

2. Oil leaks

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 a lot of 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 to a small vacuum. If the oil cap just flies away together with a lot of smoke that pours out – you may have bad piston rings.

3. Weak Acceleration

When the piston rings get damaged, the engine’s combustion chamber loses pressure. This causes the engine to lose power since the piston is not able to 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, you will get higher compression and you will feel an immediate change in your vehicle’s power.

3. Blue Smoke Emitting from Exhaust 

Not only will wear 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 it 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 larger repair cost.

How to check the piston rings

The easiest way to test the piston rings is with a leak-down-tester. This tool will measure the amount of air that is leaking down from the combustion chamber into the crankcase.

If you do not have this tool, you can also check the combustion chamber easily by letting the engine run on idle and removing the oil cap. The engine should have a slightly to non-vacuum pressure if it’s healthy. If the oil cap flies away when you are just putting it on top of the valve cover together with pouring out a lot of smoke – it means that you have too high pressure in the engine.

This can be caused by 2 different things – either bad crankcase ventilation or too much leak-down from the combustion chamber. Check the crankcase ventilation and make sure the pipes are not clogged.

Replacement Cost

Piston rings are small but they are expensive to replace. It basically depends on the make and model of your car but on an average, you could expect to pay from $40 to $200 just for the piston rings. That doesn’t sound much but wait till 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 8 hours or more for the complete job. A certified mechanic will probably do it faster and more likely in the correct way.

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

You can expect a labor cost between 1000-3000$ for a correct piston ring replacement, depending on the engine.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

Comments
  1. Hi!
    My engine’s got low compresion on one of the cilinders.
    Dealership tells me to replce the engine, but i want to know if there is a way of fixing this problem without changing the entite engine.

    Thank you.!

  2. Due to a very high demand and high ammount of comments, you have to wait for some time for your car questions to get answered. If you want to get fast answers from a certified master technician you can ask your questions here:
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