Why Do Piston Rings Go Bad? (Top 5 Reasons Explained!)

Motorcycle Piston

Piston ring damage is a big headache since it involves removing the engine cylinder head and then the piston itself. A costly affair for sure!

So, why do piston rings go bad? Here are the main reasons why pistons rings go bad:

  1. Engine oil is low or of poor quality
  2. Air filter is letting in dust
  3. Oil filter is not working right
  4. Engine blowby
  5. Fuel flooding in carburetted engines

Without further ado, let’s deep dive into each of these causes and their solutions.

What Causes Piston Rings To Go Bad

The piston rings close the gap between the cylinder walls and the piston and ensure that the fuel mixture does not enter the crankcase. Here is our guide on piston rings that discusses their function in depth.

If the piston rings go bad, you need to remove the engine to replace them. That’s a labor-intensive as well as costly process.

Let’s discuss each of the causes leading to engine piston rings going bad, getting damaged or worn-out.

#1: Engine Oil Is Low Or Of Poor Quality

The first and foremost reason for piston ring wear and damage is low or poor quality engine oil.

Engine oil is vital for lubricating the engine components. And piston rings need to form a thick film so that there won’t be metal-to-metal friction with the cylinder walls.

Now, if the engine oil levels are low or the oil is of poor quality, there won’t be sufficient lubrication when the piston rings rub the cylinder walls during the to-and-fro movement of the piston.

As a result, the strong metal to metal contact between the rings and the cylinder’s inner walls results in the wear and damage of the piston rings and even the damage of inner walls of the cylinder.

#2: Air Filter Is Letting In Dust

If the air filter is not working properly and filtering the dust from air particles, there can be damage to the piston rings.

When the dust enters the engine, since air filters are not filtering them, these particles start getting accumulating on the cylinder walls. And bit by bit, slowly and steadily, they start to ear out both the piston rings and the cylinder inner walls.

Of course, this is not sudden damage to either piston rings or the cylinder walls. But, it is a slow process and it eventually gets so bad that you need to remove the piston rings and replace them, and for the cylinder walls, you have to re-bore the cylinder for further usage.

#3: Oil Filter Is Not Filtering Right

Another source of contamination is the oil filter not filtering right.

When the engine oil has lots of contaminants and grit, it again starts accumulating and over time, damages both the piston rings and the cylinder walls.

Eventually, the only solution remains that one needs to replace the piston rings and re-bore the cylinder to get a clean inner cylinder wall.

In a way, the oil filter problem is much more serious than that of the air filter problem. This is because the oil film needs to be continuously present between the piston rings and the cylinder walls to avoid metal to metal friction.

And the oil contaminants and grit accumulating there worsens the situation by gradually damaging both the piston rings and the cylinder walls.

#4: Engine Blowby

Engine blowby happens when the fuel mixture in the combustion chamber trickles down along the gaps between the piston and the piston rings.

As a result of this tricking down of the fuel mixture, the fuel which is getting burnt will also burn the piston rings, engine oil along the piston walls as well as the piston grooves.

Although the main effect of engine blowby is low compression and loss of power in the engine, it also results in the damage of piston rings – mainly the compression ring.

To know more, here is our explainer on engine blowby’s cause and symptoms.

#5: Fuel Flooding In Carburetted Engines

Fuel flooding occurs when a rich mixture enters the engine and is unable to detonate completely. As a result, traces of unburnt fuel remains inside the engine.

Now what this unburnt fuel does is it starts accumulating and replacing the thick oil film along the cylinder walls.

If the lubricating oil has not formed a thick layer, the unburnt fuel will easily replace them.

As soon as the fuel replaces the oil, the piston rings and the cylinder walls will start to have close metal to metal contact since there is no more oil lubricating them.

As a result, continuous metal to metal friction will start between the rings and the inner cylinder walls until the fuel has been removed from the engine through exhaust ports.

If this cycle of fuel flooding keeps on continuing, then the metal to metal friction will increase dramatically, resulting in damaged piston rings.

Symptoms Of Bad Piston Rings

So, once these piston rings go bad, how would you know that these piston rings are damaged or worn out?

What are the signs of bad piston rings?

Here are the symptoms of bad or worn-out piston rings:

  1. Excessive engine oil consumption
  2. White smoke from exhaust
  3. Low compression in the engine
  4. Decreased power and acceleration
  5. Piston slapping

For more details, here is our post on signs of bad piston rings.

How To Prevent Piston Rings Damage

In order to prevent your piston rings from going bad, you need to ensure all the above mentioned causes for piston ring damage do not happen.

Firstly, use good quality engine oil and ensure that the oil levels are not low. This is one of the primary things to be taken care of since it not only affects the piston rings but almost all the engine components.

Second, make sure the air filter and the oil filter are clean. If these filters allow dust and contaminants to flow through them, then these contaminants will start accumulating and will result in damaged piston rings. So, ensure that these filters are maintained properly.

Next, make sure the piston rings are fitted properly so as to avoid engine blowby. Engine blowby, along with damaging piston rings will also impact engine power and performance.

And lastly, ensure there won’t be fuel flooding of the engine. Tune the carburetor for the right air-fuel mixture so that the engine does not receive an extremely rich fuel mixture for combustion.

These preventive measures should easily help in piston rings’ maintenance and will ensure that the piston rings last long without much damage.