A car’s piston rings regulate engine oil consumption and oil pressure. Therefore, when the piston rings fail, the car will experience a myriad of problems that may ultimately damage the entire engine.
Although piston rings are some of the least expensive parts of a car engine, they are essential to the effective operation of the vehicle. Several symptoms of bad piston rings can let you know when you need to replace them to avoid critical engine damage.
What Is a Piston Ring?
A piston ring is a metal ring that fits around an engine’s piston, sealing the piston and cylinder wall together. Piston rings are crucial because they:
- Support engine efficiency and power: Since it seals the piston and cylinder wall together, a piston ring prevents combustion gases from leaking into the oil sump. That connection helps maintain the engine’s power and efficient operation.
- Protect components from friction and wear: Piston rings apply pressure to cylinder walls, providing a consistent oil film for lubrication. This film protects the cylinder’s working surfaces from friction to prevent or reduce wear.
- Maintain proper temperatures: A piston ring helps transfer heat from the piston to the engine’s cylinder wall, where it transfers to the system’s coolant. They are essential for preventing overheating and maintaining piston stability.
- Control oil and emissions: Piston rings help remove excess oil from the engine’s combustion chamber. They help regulate oil consumption, which reduces emissions.
Different Types of Piston Rings
Modern vehicles are commonly installed with three piston rings per cylinder. Two rings to hold back combustion fumes and the other holds and direct engine oil where it should go in the vehicle. Here are the different piston ring types and their functions in the engine.
#1. Pressure Compression Rings.
Compression rings prevent gas leakage by sealing the top of the piston. These rings are commonly on the primary piston grooves but different car models can have them located differently.
These rings also transfer heat to the piston walls from the piston. The compression rings shear the oil layer left by the oil ring.
#2. Wiper Rings.
Wiper rings provide a backup to the pressure compression rings. They are below the compression rings and are responsible for cleaning the excess oil from the liner surface. They also help the compression rings to stoop any possible gas leakages.
Wiper rings are tapper angle faced directed towards the bottom to adequately wipe oil simultaneously with piston and crankshaft motion.
Improper positioning of the wiper rings causes excessive oil consumption because the rings wipe off more oil at the combustion chamber.
#3. Scrapper Oil Control Rings.
According to their name, oil control rings regulate the lubrication oil amount that moves through the cylinder walls. The rings evenly distribute the oil around the liner circumference.
Scrapper rings scrub off the oil splashed on the cylinder walls. They disburse this scrapped oil back to the crankcase. They also prevent oil from passing the narrow space between the ring and the cylinder.
Piston Rings Location
The piston rings are located inside 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.
Common Symptoms of Bad Piston Rings
Several things can help you identify if your piston rings are wearing out. The most common symptoms are listed below.
#1. An Increase in Exhaust Smoke.
One of the obvious symptoms of bad piston rings is having too much smoke coming out of the exhaust of your car.
In addition to an increase in the amount of exhaust smoke, this smoke will have a somehow burning smell and will appear darker than usual.
It has a dark grey appearance because engine oil is leaking to the combustion chamber because the piston rings have failed to seal efficiently.
#2. Excess Oil Consumption.
The moment your check engine light turns on because of excess oil consumption, it is highly likely that your piston rings need replacement.
Worn-out piston rings will lead to oil leaks in the combustion chamber which automatically will manifest themselves as more oil consumption by the vehicle. So check the Engine oil Level Regularly.
Therefore, your car will require you to regularly add oil more frequently than the average 4000 miles before refill. Immediately inspect your piston rings when your car begins consuming more than the regular amount of oil.
#3. Decreased Acceleration.
Piston rings regulate compression and lubrication. Therefore, when your piston rings wear out and you lose compression and you have inadequate lubrication, the vehicle will lose its acceleration power.
The car will struggle to accelerate when you step on the gas pedal and the engine will take longer to respond and speed up your maneuver.
Decreased acceleration can also be due to spoilt valve seals. Therefore perform a compression test to distinguish whether you have bad piston rings or valve seals.
Higher compressions are symptoms of bad valve seals while low compression means your piston rings are damaged.
#4. Poor Engine Performance.
As mentioned above, loss of compression delays acceleration due to inefficient engine rotation which leads to engine stall.
In extreme cases, you may lose all engine power and you may need to tow your vehicle when the engine malfunctions on the road due to bad piston rings. Minor cases only lead to poor engine performance.
Complete engine stall will only occur if you ignore the early symptoms of bad piston rings and continue to use the car without taking it to the mechanic for inspection.
#5. Dirty Air Filters.
An increase in the oil intake is often because of blow-by when the air-oil mixture in the combustion chamber leaks past the installed piston rings to create more pressure in the engine crankcase.
When pressure vents from the positive crankcase ventilation (PCV) hose back to the crankcase then there will be a large amount of blow-by and the air intake will be very oily. Oily intake will also result in increased oil consumption.
What Causes Piston Ring Failure?
Piston rings don’t last forever, and when they start to fail, it can have serious consequences for your engine. Before undergoing any repair or replacement measures, you first need to identify the underlying cause.
#1. Wear and tear.
Piston rings are subjected to constant friction and high temperatures generated during engine operation. Over time, this wear and heat can gradually erode the rings’ surfaces.
As the rings wear down, they lose their ability to create an effective seal against the cylinder walls.
This means that the gap between the rings and cylinder walls widens, allowing gasses to escape past the rings during the compression and combustion strokes.
This escape of gasses results in reduced engine efficiency and power, as well as increased oil consumption.
#2. Cylinder scoring.
Cylinder scoring refers to the presence of abrasions or scratches on the inner walls of the engine cylinders.
These abrasions can occur due to contaminants present in the engine oil, such as dirt or metallic particles, or as a result of inadequate lubrication.
When piston rings travel over these damaged areas, it exacerbates the problem. The damaged cylinder walls cause accelerated wear on the rings, leading to a compromised seal.
This diminished sealing performance further contributes to reduced compression, engine power, and increased oil consumption.
#3. Overheating.
Elevated engine temperatures can result in the distortion of piston rings. This occurs when the rings, which are typically made of metal, lose their intended shape and elasticity due to excessive heat exposure.
Various factors can lead to engine overheating, including a malfunctioning cooling system, continuous operation under heavy loads, or excessive engine overheating due to factors like insufficient coolant levels or a malfunctioning thermostat.
Distorted piston rings are less effective at maintaining a tight seal, which can lead to compression loss and poor engine performance.
#4. Poor maintenance.
Neglecting routine engine maintenance can significantly impact piston ring longevity.
When maintenance practices such as skipping or extending oil change intervals, using an inappropriate oil viscosity, or operating with low oil levels are observed, the consequences can be detrimental.
Insufficient or contaminated oil can increase friction between the rings and cylinder walls, accelerating wear. This leads to premature ring deterioration, compromised sealing, and a shorter service life.
#5. Detonation and pre-Ignition.
Detonation and pre-ignition are abnormal combustion processes that generate high-pressure shockwaves within the combustion chamber.
These shockwaves can exert significant stress on the piston rings, potentially causing them to deform or lose their seal integrity. This results in compression loss, poor engine performance, and increased wear on the rings.
#6. Incorrect installation.
Incorrect installation of piston rings can have detrimental effects on their performance. If the rings are not positioned correctly, such as being oriented in the wrong direction or not properly seated in their grooves, they may fail to create an effective seal.
This misalignment can result in rapid wear and reduced sealing capability, leading to compression loss.
#7. Excessive carbon deposits.
Carbon deposits can accumulate on the piston rings over time, particularly when oil is not of high quality or when the engine operates under conditions that promote carbon buildup.
These deposits can cause the rings to become sticky or hinder their free movement within their grooves.
When piston rings do not move freely, they cannot effectively seal against the cylinder walls, contributing to compression loss and increased oil consumption.
When Should You Replace Piston Rings?
Knowing when to replace a piston ring helps prevent costly engine damage. Here are the key situations when piston rings should be replaced:
#1. When Oil Consumption Increases Abnormally.
If you find yourself topping up engine oil more often despite no visible leaks, worn piston rings may be allowing oil to enter the combustion chamber.
#2. When the Engine Loses Compression.
Reduced compression causes difficulty starting, low power, poor mileage, and weak acceleration. A compression or leak-down test usually confirms ring wear.
#3. When the Engine Feels Weak or Underpowered.
If your engine struggles to accelerate or feels sluggish, worn rings may be failing to seal the combustion chamber properly.
Repairing and Replacing Bad Piston Rings
When you suspect that your piston rings are bad, quick action can prevent more costly damage to your engine. Here, we’ll briefly cover how you can repair or replace bad piston rings.
Tools and Supplies Needed
For this job, you’ll need a range of tools and supplies, such as:
- A piston ring compressor
- A torque wrench
- Gasket sealant
- New piston rings
- A set of socket wrenches
- Feeler gauges for checking gaps
- Engine oil
Step 1: Preparing the Engine.
The first step in the repair or replacement process is to prepare the engine for disassembly. This usually involves draining the oil and coolant, disconnecting the battery, and removing various engine components like the intake manifold, exhaust manifold, and cylinder head. Depending on the vehicle, you might also need to remove the engine from the car.
Step 2: Removing the Old Piston Rings.
You’ll have to detach the connecting rod caps to free the pistons. Then, use a piston ring expander or a pair of needle-nose pliers to remove the worn rings carefully.
Step 3: Installing New Piston Rings.
Installing new piston rings involves multiple steps. Here’s a quick step-by-step guide:
- Check the fit of each new ring in the cylinder using a feeler gauge.
- Apply a small amount of engine oil to the new rings and piston.
- Use a piston ring compressor to squeeze the new rings onto the piston.
- Gently lower the piston back into the cylinder, ensuring the ring gaps are properly aligned.
- Reattach the connecting rod caps and torque to manufacturer specifications.
Step 4: Engine Reassembly and Testing.
After installing the new rings, you’ll need to reassemble the engine, following the reverse order of the disassembly process.
Once reassembled, fill the engine with fresh oil and coolant, then run a series of tests to ensure that the new piston rings are functioning as they should.
How to Prevent Piston Ring Failure?
Below are the most effective ways to prevent piston ring failure and improve the overall life of your engine:
#1. Strict maintenance schedule.
Adhering to a meticulous maintenance schedule is pivotal in preserving the integrity of piston rings and overall engine health.
Routine oil and filter changes
Regular oil and filter changes are fundamental for minimizing wear on piston rings. Engine oil serves as a lubricant for various engine components, including the rings.
Over time, oil degrades and accumulates contaminants, leading to increased friction and wear.
Changing the car oil and filter at recommended intervals, usually every 3,000 to 5,000 miles depending on the vehicle and oil type, ensures that the engine remains properly lubricated.
Use of manufacturer-recommended oil grade
It’s imperative to use the oil grade specified by the vehicle manufacturer. Different engines require specific oil viscosities and formulations to operate optimally.
Using the recommended oil grade helps maintain proper lubrication, preventing premature wear and damage to the piston rings.
#2. Avoiding overheating.
Malfunctions in components like the thermostat, radiator, or water pump can disrupt the engine’s cooling capacity.
Additionally, flush and replace coolant to prevent overheating and cylinder scoring, which can damage piston rings.
#3. Timely repairs.
Addressing engine performance issues promptly is crucial to prevent further harm to the piston rings:
- Fixing ignition problems: Misfires or a malfunctioning spark plug system may cause irregular combustion and increased stress on the rings.
- Addressing fuel system issues: Fuel system problems, such as clogged injectors or a failing fuel pump, can affect combustion efficiency.
- Resolving exhaust system malfunctions: Malfunctions in the exhaust system, including issues with the catalytic converter or oxygen sensors, can lead to abnormal combustion and potential piston ring stress.
#4. Engine break-in.
During an engine rebuild or piston ring replacement, follow manufacturer-recommended break-in procedures. This typically involves gradually increasing engine load and avoiding high RPMs during the initial break-in period.
These procedures allow the new rings to seat correctly and form a proper seal against the cylinder walls, ensuring optimal performance and longevity.
FAQs.
Most people ask, how long can I drive with bad piston rings? It all depends on the extent of their damage. However, here are the answers to the most frequently asked questions by car owners with piston ring problems.
Q: Can you just replace piston rings?
After performing piston ring failure analysis, ideally, you should replace piston rings together with the ring spacer.
That is because bad piston rings hone and de-glaze the cylinder leaving the grooves damaged. Remove the top ring ridge on the bore to avoid the ring smashing with the ridge.
Since you already have the engine out, you can also check and replace bearing shells and check for lapping in the valves.
Q: What does a broken piston sound like?
A broken piston causes a rattling and knocking sound when running. The rattling sound of a broken piston is difficult to miss. Bad piston rings sound will be accompanied by misfiring and engine knocking.
Q: Is it cheaper to rebuild an engine or replace it?
Depending on the kind and extent of the problem on your hands, it is unlikely that rebuilding an engine can be less expensive than replacing it. Most engine parts are quite costly and require you to purchase other parts simultaneously when they malfunction.
You can avoid having to replace or rebuild your engine by regularly servicing your vehicle to fix what causes piston rings to fail before waiting for them to wear out.
Q: Can bad piston rings cause a misfire?
When you have bad piston rings or the valves, cylinder walls, or a head gasket leak, the vehicle engine will stall causing misfiring.
You will notice white smoke from the engine that means that the worn-out and damaged piston rings can no longer seal the cylinder adequately.
Final Words
Piston rings are crucial parts of a vehicle’s engine. They may easily be ignored but can cause major damage to the vehicle because the engine will lose the compression necessary for avoiding oil leaks.
You will notice failing piston rings by the increase in oil consumption by the car and the increase and change in smoke color.
Ensure you visit a mechanic regularly to check and replace your piston rings as soon as you sight any of the symptoms of bad piston rings, motorcycle, or car as soon as possible.