Valve seals and piston rings are essential parts of your engine. They keep the pressure in and the motor oil out.
If the valve seals or the piston rings become defective, they will require replacement.
You’ll immediately notice some obvious symptoms: low power and increased oil consumption.
In this simple guide, I will explain what to watch out for.
So without any additional ado, let’s get into it.
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What Are Valve Seals?
Within an engine, valves open and close. Intake valves allow the air (or air/fuel mixture, depending on the engine type) into the chamber. Exhaust valves permit the used gases out through your exhaust pipe.
Cylinders typically have one or two valves inlet and exhaust valves each.
Valve stem seals are made from durable rubber.
Their main jobs are:
- They sit around the valve stem and prevent pressure from escaping.
- They stop oil from entering the combustion chamber through the cylinder head.
Valve seals are like any other typical rubber seal, but they’re quite tiny – about the size of your fingertip.
What Are Piston Rings?
The pistons rise up and down within the motor cylinders. Piston rings surround each one of them.
Most pistons have three piston rings. The top two rings are responsible for sealing compression in the combustion chamber. The bottom one’s main function is to be an oil seal.
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- They prevent pressure from escaping the chamber.
- They stop oil from splashing into the chamber and being burned.
- They stabilize the piston as it rises and falls within the cylinder.
- They help regulate temperature, distributing heat from the piston to the cylinder walls. From there, it moves into the coolant and dissipates into the atmosphere.
Symptoms Of Bad Valve Seals And Piston Rings
Defective valve seals and piston rings seal the top and bottom of the combustion chamber. As mentioned above, they keep pressure in and oil out.
Unsurprisingly, you’ll notice compression- and oil-related indicators when they deteriorate or break.
Here are some of the main symptoms you’ll notice when valve seals or piston rings wear or break.
- Increased oil consumption
- Reduced engine power
Increased Oil Consumption
If the valve seals or piston rings become inadequate, oil can go into the combustion chamber.
As a result, your car’s oil consumption will significantly increase. You’ll notice the following:
- Gray/blue smoke from your exhaust pipe. When oil burns, it creates a film. That’s what you see in the smoke.
- Low oil pressure warning lights or messages.
- Coolant overheating on the engine temperature gauge.
- Noticeably low oil levels at the manual dipstick or electronic sensor.
When your car suffers from extreme oil consumption, the leak could be anywhere in the system. Other potential causes include a blown head gasket or a faulty oil filter.
However, it could be occurring due to a defective valve seal.
Reduced Engine Power
When the piston rings or valve seals go faulty, the pressure within the chamber leaks out.
When the spark plug ignites the air and fuel, this blast is the energy that propels the piston down. If there’s somewhere for these gases – this force – to escape, there isn’t as much pressure pushing the piston downward.
With deteriorated or broken valve seals or faulty piston rings, that’s just what’s happening.
As a result, your engine’s performance will take a significant hit. You’ll notice the following:
- Sluggish under acceleration
- Difficulty reaching higher speeds
- Rough idle
- Stalling
- Shaking and shuddering from the imbalanced engine
The optimal way to check this is a pressure test, also known as a vacuum test. This uses basic air pressure and connects via the spark plug seat.
Severe pressure loss is more likely caused by broken piston rings than valve seals. They have a more substantial, more influential job.
Other spots within your cylinder could be causing this pressure leak. The cylinder wall could be fractured, for example. However, piston rings and valve seals are an excellent place to start.
How To Know Whether The Problem Is Piston Rings Or Valve Seals
Piston rings are more prone to fail than valve seals.
If your pressure test fails, you will likely find issues with the piston rings.
If the pressure test leaks its vacuum gradually, it’s more likely to be the valve gaskets
One of the most obvious symptoms of bad valve seals is significant signs of oil residue on the spark plug. It could also mean defective piston rings, but valve seals are more probable if there’s a lot of oil on the top of the plug itself.
What is the optimal way for a mechanic to see whether the problem is valve seals? They need to remove the cylinder head to look for themselves.
Oil in the cylinder head isn’t a sign of faulty valve stem seals, contrary to what you might have heard. Oil is supposed to be there. When you turn the engine off, it naturally accumulates in particular spots.
The valve seals’ functions aren’t to prevent oil from getting into the cylinder head. They’re to stop oil leaking from the head into the combustion chamber.
Replacement Cost For Bad Valve Seals And Piston Rings
If the valve stem seals are intact and in adequate condition, but the cylinder still isn’t holding pressure, you’ll need an engine rebuild. The mechanic should first rule out a blown head gasket, of course.
You should only use a skilled, reliable mechanic for this job. Unless you know your way around cars, this isn’t something you should attempt yourself.
The sole conclusive way to know whether the piston rings or something else is the primary issue is to disassemble your engine.
An engine rebuild is the only way to replace the piston rings. Reconstructing an engine isn’t a cheap job. In most cases, you’re looking at at least $3,000. The larger and rarer your motor, the greater the impact on your wallet.
Replacing the valve seals means removing the cylinder head from the block. The camshaft(s) (if overhead), rocker arms and pushrods (if you have an older engine), and spark plugs need to come out. Technicians will then switch out the seals. Expect to pay $1,000 to $1,500 for this expensive job.
Conclusion
You have a significant problem if you notice low power combined with falling oil levels. It could stem from piston rings or valve seals, although other causes are possible.
Get your engine examined and repaired as soon as possible. The longer it’s left, the more harm will be done to other components.
It’s expensive, but that’s unfortunately inevitable.
