Symptoms of Bad Piston Rings | Autance

Is it just us, or does everything important that you own happen to break at the exact same time? Maybe…

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Symptoms of Bad Piston Rings | Autance © Symptoms of Bad Piston Rings | Autance

Is it just us, or does everything important that you own happen to break at the exact same time? Maybe we’re just superstitious, but each of us every so often experience ‘one of those weeks’ where everything, from the washing machine to our favorite jumper, happens to break at once. Yet what turns one of these notorious ‘bad weeks’ into an ‘awful week’ is if something goes wrong with our cars.

Unfortunately, piston rings are one of those obscure yet costly components that our cars need to operate. By keeping our car in prime condition throughout its life, piston damage can be prevented. Yet if you’re noticing several worrying changes occurring in your car, read on to ensure its not a pricier problem than you initially anticipated.

Why are Piston Rings Useful?

Engines need piston rings to operate like human bodies require food to survive. Typically made from cast iron or steel, piston rings are split rings which fit into a groove on the outer diameter of a piston (a moving cylinder of metal which effectively operates an engine). Their main task is to ensure that by applying the correct pressure on the cylinder wall or liner, a consistent layer of oil is maintained. Other ways in which piston rings are useful are by preventing any excessive heat building up inside the piston by transferring heat from the piston crown to the cylinder.

Different Types of Piston Rings

What many of us don’t know is that two different kinds of piston rings exist inside your engine – compression rings and oil control rings. The compression rings are located in the first grooves of the piston, with their primary function being to seal the combustion gases and transfer heat from the piston to the piston walls. There usually exists both a top and an intermediate compression ring to ensure the maximum power output that your engine can offer is obtained. A piston wouldn’t be complete if it wasn’t for control rings; their task being to regulate the amount of lubricating oil passing along the cylinder walls. Control rings keep all gases and lubricants where they’re meant to be by prohibiting oil from sneaking into other engine chambers. Having all three piston rings working harmoniously is crucial for preserving the internal workings of your vehicle.

What Is Blow-By And Why Do I Want To Prevent It From Occurring?

As previously alluded to, one of the main functions of piston rings within an internal combustion engine is to maintain gas compression between the piston and the cylinder wall by sealing the cylinder. Why would this be important? This is because we want to prevent blow-by – known as the unwanted leakage of gas under pressure – as much as we possibly can.

There are two main ways in which blow-by will occur. When an engine gets older, the cylinder walls will wear out due to constant piston and piston ring scraping. This will encourage the cylinder bore to become bigger and form a gap behind the piston and the cylinder. On the exhaust stroke when the piston is moving up, the piston rings will be pressed down, giving the exhaust fumes and gases a chance to sneak around that gap. On your intake stroke which occurs after your exhaust stroke, the pistons will then move up. As they rise and hit the top of the piston, harmful gases can now pass underneath them and travel down, eventually making their way into the crank case.

Another way in which blow-by can occur is by the gases passing through the piston ring gap itself. When analyzing a piston ring on a piston, there should be a gap on the ring which exists so that the piston ring can act like a spring. This encourages sealed compression; which can be ensured due to the ring expanding and contracting with the heat and meeting up with the cylinder walls so that the chamber will be sealed. Unfortunately, over time, the constant scraping of the piston rings wears them down and sealed compression doesn’t occur as naturally. The gaps will allow for other combustion gases to sneak through the backside of the ring and inevitably get down within the crank case.

Symptoms of Bad Piston Rings

‘Your piston rings are damaged’ are the five words any driver dreads to hear from a mechanic. What are the signs that your piston rings may be worse for wear? Read on to see if your piston rings are on their way out.

  • Gray or White Smoke Coming Out from the Car Exhaust

I mean… this one is a pretty obvious sign that something isn’t right with your vehicle. When we see any sort of smoke rising from an exhaust, this won’t be your car telling you that everything is fine and dandy. When piston rings are damaged then engine oil will start to leak into the combustion chamber, causing the oil to burn and emit thick gray and white smoke from the engine. Not a good situation to be in.

Top Tip: Pay attention to the color of the smoke emitting from your vehicle. Black smoke usually indicates problems with fuel consumption with blue smoke suggests there is something awry with oil levels in the combustion chamber. On the other hand, white smoke implies that there’s something wrong with either the injectors, damaged values, or piston rings in the engine of your car.

  • Increase in the Amount of Oil Consumed

Does it recently feel like your car is guzzling through oil at twice the speed it used to? This excessive oil consumption that you’ve became aware of could be a sign of bad piston rings. As mentioned previously, oil from the engine will leak into the combustion chamber if the piston rings are worn out. This means less oil will be present in the car’s engine. If you’re having to add oil before the standard 3,000 to 5,000-mile mark then this is usually indicative of additional problems.

  • Difficulty Accelerating

Having trouble accelerating? Engine power will decrease along due to the reduced compression which occurs when the piston rings are damaged. We beg of you, do not wait until this gets worse!  The need for speed will be the least of your worries if you decide to struggle on with low acceleration power. In the worst of cases, a driver can lose all engine power and your vehicle won’t be able to accelerate at all. We suggest avoiding the embarrassment and cost of hiring a tow truck in front of all the neighbors to haul your vehicle to the nearest mechanic and drive there yourself.

Replacing Piston Rings – Will This Be Costly?

As you’ve probably guessed, replacing piston rings will not be cheap. On average, mechanics charge from $1500 up to around $2500 for this kind of job. Many customers tend to hear a figure within this price and believe they’re getting ripped off. We assure you, this is not the case. This job is a very complicated and daunting task as the car engine must be completely dismantled, the cylinders reconditioned and, the car completely reassembled at the end of the process.

If you enjoy a little DIY, replacing your own piston rings is no easy task. If you’re unsure about tackling this daunting task by yourself this is more than fair – the large majority of drivers take their vehicle to a garage to be serviced. After all, any mistake made would be incredibly costly!

One common debate ubiquitous within the automotive world is if pistons can be reused. Although a piston may look like they’re in excellent condition, they often have worn upper ring lands and have loosened with time. We’d recommend almost always purchasing a new piston but if you’re adamant that yours is in good condition, measure each section carefully and check the fit of the wrist pin before inserting.

How to Prevent Worn Out Piston Rings

Want to avoid having to deal with bad piston rings for the foreseeable future? The trick is simple: ensure that the rest of your car is working efficiently.

  • Engine Coolant – Do you have enough engine coolant inside your vehicle? Double check by opening up the radiator cap when the engine is cold or by looking at the water in the coolant reservoir.
  • Spark Plugs – When were your spark plugs last changed? Pistons can be damaged when subjected to extremely high combustion temperatures and by reading the spark plug, you’ll be able to tell heat is too high if the electrodes are melted or damaged.
  • Antifreeze – What color is your water? By maintaining the correct level of antifreeze, temperature is kept optimal and your engine protected.

By maintaining other parts of your vehicle regularly, we hope you won’t have to refer back to this article in the foreseeable future. Remember, happy piston rings make for a happy car!

Related Post: Antifreeze in Oil: What You Should Do


  1. Piston ring – Wikipedia
  2. How to Replace Piston Rings – DoItYourself
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