Valve seals and piston rings can have little significance, but the failure of these last barriers causes oil burning, compression loss, and issues.
Learn how to tell the symptoms of bad valve seals and piston rings before the real damage occurs to the engine, but don’t be too shocked when you hit the Replacement Cost sections below. It could still be worse.
Functions of Piston Rings
Piston rings are installed between the piston and cylinder and complete four different tasks:
- Compression Seal: The ring produces a seal that stops combustion gases from leaking from the chamber. Leakage will greatly reduce engine power.
- Heat transfer: Each time there is a combustion event, heat rapidly rises in the chamber. High temperatures can cause serious problems, and a piston ring helps transfer the remaining heat from the piston head to the cylinder to lessen the threat of heat problems.
- Lubrication Control: Keeping the piston lubricated uses a film of oil. The piston ring is crucial in controlling how much oil becomes available to the piston.
- Piston Support: Since the piston rides on a crank, it could easily slam into the cylinder wall if not for the padded piston support of the piston ring.
Piston rings do wear out, so you will eventually have to replace them.
The Function of Valve Stem Seals
As the valves control how much of the fuel mixture gets to the cylinder, of course, the valve itself has a seal( and many times a protective sleeve), which helps reduce leakage of combustion gases and helps the oil not leak down into the engine from the main engine area.
The seals are made from a super-strength rubber material and can be installed in small collars, which are the and most upper part of the valve stem.
As these valve seals begin to wear out, you’ll start to see some major symptoms that are specific to this failure.
Symptoms of Bad Valve Seals and Piston Rings
Piston rings and valve seal symptoms are quite similar to each other. In fact, when one fails, the performance of the vehicle will diminish, and other symptoms will also appear. Below are some symptoms of the warning signs of these components failing.
#1. Blue-Gray Exhaust Smoke.
When you see blue-gray or light-gray exhaust smoke, it usually means your car is burning oil.
This smoke means that it is leaking into the combustible chamber in your engine. This oil leak could be caused by various issues, including bad valve seals or worn piston rings, a leaking valve cover gasket, among many others.
You will usually notice a stronger amount of this smoke when you start your car after sitting for a while (like, after a long night), or when you are accelerating hard.
#2. Too Much Oil Being Used.
If your piston rings wear out or your valve seals shear off, oil can leak into a space in your engine where it should not belong, like your combustion chamber. Then your engine will use its oil much faster than it normally does!
You may notice that you have to add oil more often in between oil changes, or that the oil in your engine drops quickly over the next few weeks. Remember – some oil consumption is normal, especially if your vehicle is older or high mileage.
But if you are adding a quart or more of oil, in between scheduled oil changes, you might want to have your engine checked.
Also know that there’s no such rule that only one component may be leaking oil at any one time, so if you replace a seal or gasket somewhere and you’re still losing oil, start checking for additional sources of oil loss.
#3. Poor Acceleration.
If the piston rings and valve seals sustain damage, they will lose compression, and this will cause you to lose engine power. Therefore, you will be unable to accelerate as you would normally do when you press the gas pedal.
While bad valve seals and damaged piston rings have similar symptoms, the difference in time and cost to repair them is immense. Figuring out exactly which one is bad by yourself will save you both time and money when you take it to the mechanic for repair.
Both valve seals and piston rings can become damaged and cause a loss of engine compression. Loss of compression means that you’re losing engine power, which you’ll probably feel more distinctly when you try to accelerate.
When you press the gas pedal, your car may feel sluggish or unresponsive, as it takes longer to reach its higher speeds and struggles more on inclines. Power loss can be a slow process, so you may not see it immediately.
#4. Increased Oil Spots Under Vehicle.
Bad valve seals and piston rings can cause oil to leak into places it’s not supposed to go, which can lead to leaking externally to the outside surfaces of the engine. Consequently, you may notice more oil spots on your driveway or parking space when you haven’t moved your car for a while.
These oil spots may start small but can become larger in extent. Although it is normal for older cars to leak from time to time, a noticeable increase in oil spots can indicate that there are internal issues with the engine and may imply greater issues ahead.
#5. Rough Idle or Misfires.
When the valve seals or piston rings fail, they let the oil seep into the combustion chamber when the engine is cold. When oil has developed in the combustion chamber, it will not allow the spark plugs to do their job effectively, which can cause a rough idle or misfires.
This means that you may notice that your car shakes or vibrates more than usual when it is stationary (easily identified when you have just started the car, particularly in the morning).
It can also result in the engine stumbling or hesitating when it is trying to accelerate. It’s common for these issues to diminish as the engine warms up, but don’t ignore them.
#6. Less Fuel Efficiency.
Damaged valve seals or piston rings will not maintain proper compression in the combustion chamber. If compression is lost, the engine needs to work harder to do the same amount of work and make the same power, leading to heavier fuel consumption.
This loss of fuel efficiency can happen slowly, so you may want to track your fuel consumption over time to slowly identify patterns when you’re driving.
If you notice a loss of efficiency and fuel consumption suddenly drops without changes in your driving habits, you likely have an internal engine issue inconsistent with maintenance or repairs needed, and it may be due to your piston rings or valve seals.
Cost of Replacing Piston Rings
The cost for replacing piston rings will vary by several factors, including the make and model of your vehicle. You should have in mind the type of engine in your vehicle and the condition of your engine.
The cost for a mechanic to perform this job will typically be a minimum of $1,500 and be upwards of $2,500.
The cost for this replacement job is so high since it is extremely complicated. The engine will have to be fully disassembled, and the cylinders must be reconditioned.
Then the car will have to be fully reassembled. Only an experienced and skilled mechanic will be able to complete the disassembly and reassembly in a reasonable time. This task will take several hours.
Cost of Replacing Valve Seals
If you know the valve seals are damaged, then have a certified auto mechanic replace the oil seals. Depending on the make and model of the vehicle, the cost will be between $900 to $1,800.
When the valve seals are replaced, the engine will have to be disassembled until you can access the valve spring.
Remove the rocker arms, pushrods, the spark plugs, and the cylinder head cover. The time this takes depends mostly on the make and model of the vehicle.
Sometimes the auto mechanic will need to disassemble and remove the cylinder head, and rebuild it with a cylinder kit that has a cylinder head gasket.
Compression Test Diagnostic
A compression test is a useful diagnostic measuring tool to find problems with valve seals and piston rings. A compression test measures the pressure in each cylinder at the point the piston is during the compression stroke of the engine cycle.