3 Symptoms of Bad Valve Seals and Piston Rings and Replacement Cost

Last Updated on October 19, 2021

In this article, we’re going to discuss the symptoms of bad valve seals and piston rings, as well as their basic functions and common replacement costs. Valve seals and piston rings are crucial for your engine to function.

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If you learn to recognize the warning signs for these components, you’ll be able to replace them before any serious damage is done to your engine.

Functions of Piston Rings

Piston rings are located between the piston and cylinder and provide four different functions:

  1. Compression Seal:  The ring creates a seal, preventing combustion gasses from leaking out of the chamber. Leaks can drastically reduce engine performance.
  2. Heat Transfer:  Every time combustion occurs, the internal temperature of the chamber spikes. These high temperatures can cause serious damage. A piston ring helps transfer this excess heat from the piston head to the cylinder, reducing the risk of heat damage.
  3. Lubrication Control:  A film of oil is necessary to keep the piston lubricated. The piston ring helps regulate the amount of oil that reaches the piston.
  4. Piston Support: The piston works on a crank and could easily bang into the cylinder wall if not for the piston ring’s padded support.

It is important to note that piston rings wear out, which means you’ll likely need to have them replaced at some point.

Functions of Valve Stem Seals

Valves regulate how much of the fuel mixture enters the cylinder. The valve itself has a seal (and sometimes a protective sleeve) to help prevent leakage of combustion gasses and prevent oil from leaking into the main engine area.

These seals are commonly constructed out of a super strength rubber material and they’re placed into a small collar of the valve stem’s top area. Once these valve seals start to wear out, you’ll begin to notice some major symptoms that are unique to this problem.

Symptoms of Bad Valve Seals and Piston Rings

Bad valve seal or piston ring symptoms are quite similar. Whenever either fails, the performance of the vehicle will drop,  and other symptoms will manifest. Let’s take a look at some warning signs that these components are going bad:

#1 – Exhaust Smoke

If you notice thick smoke that’s blue-gray or light-gray, this is a good indication your car is burning oil. It’s a sign that oil is leaking into the combustion chamber of your engine.

See Also: 4 Symptoms of a Valve Cover Gasket Leak

#2 – Too Much Oil Being Consumed

check engine oil

As mentioned above, if the piston rings are worn out or the valve seal is broken, oil will begin to leak into the combustion chamber. This causes your engine to use up its oil supply much quicker.

#3 – Not Enough Accelerating Power

reasons and causes of car not accelerating

When there is damage to the piston rings and valve seals, compression will be reduced. This causes you to lose engine power. As a result, you won’t be able to accelerate like normal when you put your foot on the gas pedal.

Although bad valve seals and piston rings have similar symptoms, the time and costs of repairing them are quite different. Learning to pinpoint which one is bad by yourself will help save both time and money when taking it to a mechanic for repair.

You can do a compression test to help pinpoint the problem. Remove the EFI fuse and crank the engine. Then check the results on the compression gauge.

In the event your compression test results appear to be average or higher, the valve seals are likely the problem. However, low compression usually indicates that the piston rings are your problem.

To further confirm worn piston rings are the problem, do a wet compression test. Here you open the spark plug and inject a bit of oil (about a tablespoon) into the cylinder. If the compression increases, your piston rings are bad.

Piston Rings Replacement Cost

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piston ring replacement cost

When replacing piston rings, the cost will be determined by several factors. The make and model of your vehicle is one example. You also have to consider the type of engine that’s in your car and its condition.

Most mechanics will charge around $1,500 minimum for this task, up to about $2,500.

The reason this replacement job is so expensive is because it can be quite complicated. The engine must be completely disassembled and the cylinders reconditioned.

After that, the car is reassembled. Only an experienced mechanic can perform this task efficiently, requiring several hours to do so.

See Also: Piston Damage From LSPI

Valve Seals Replacement Cost

valve seal replacement cost

If you have discovered there is damage to your valve seals, then have an auto technician install new oil seals. The cost of this replacement job will be between $900 and $1,800, depending on the make and model of your vehicle.

The process of replacing valve seals involves disassembling the entire engine until you can reach the valve spring.

Remove the cylinder head cover, the spark plugs, pushrods, and rocker arms. How long this will take depends primarily on the make and model of your vehicle.

Sometimes the technician will have to dismantle and remove the cylinder head, then use a cylinder kit which contains a cylinder head gasket to replace it.

Read Also: Rear Main Seal Replacement Cost


68 thoughts on “3 Symptoms of Bad Valve Seals and Piston Rings and Replacement Cost”

  1. Hello there. Great article, very helpful.

    With regards to symptom no. 1 below – are you talking about smoke just during startup after a long period (overnight) and then smoke clears? Or smoke while engine and vehicle is running? I have a 2008 Land Cruiser that emits kinda thick white-grayish smoke during startup in the morning and clears after 2-3 minutes.

    #1 – Exhaust Smoke
    If you notice thick smoke that’s blue-gray or light-gray, this is a good indication your car is burning oil. It’s a sign that oil is leaking into the combustion chamber of your engine.



    • I would put money on your valve guide seals with the condition you described. Especially if the smoke billows out upon a cold start up and then goes away after a few minutes of driving. What happens is the oil settles inside the valve train area of the cylinder head after shut down of the engine and starts drooling downward, past the valve guide seals, running down the shaft of the valve and eventually into the combustion chamber and collects there until the engine is started again, which is why it smokes so much in the morning.. hope this helps.

      Jason Martini
      ASE Certified Technician
      Portland, OR

  2. I have a 1995 GMC picku 1/2 ton 350.engine 156000 miles one times it will have a engine rattle and smoke at the same time the clears up. No rattle no smoke. It may go 15 mile or so then does it again. No heat changes or oil pressure changes. It does use a little oil. Maybe a quart between changes. Any ideas.

  3. Hello, So my truck broke down on me ( it started lurching/choking) on my way home and so i brought it into a shop and the guy off top told me i needed to replace the motor that it was going to seize up any mile now and that was going to be like $6,000 or more, I had drive it about 10miles (from it breakingdown) before i brought it in . i cant afford a motor so i just took it home about 3miles.
    Got some other possibilitys from a couple mobile mechanics and ending up bringing it back to the repair shop. i asked them to have my heads checked instead of replacing the motor .
    when i returned they showed me a broken valve spring said that was my problem. and it would be about $1,500 to fix, they finally finish it about 2 months later and give me a bill for almost $4,000 dollars. ?!?

    but in the repairs there is nothing about a valve spring being replaced?
    it just says remove and replace left cylinder head x’s 2 and a head test and a bunch of parts and fluid changes ??

    Idk i dont know anything about this but it just seems way super high? if someone could give me some in site on what my invoice would look like to replace a left valve spring? I have a 2009 GMC Denali sierra with a 6.2 engine

    • to replace a valve spring is a relatively easy job.its just removing your rocker cover and then swapping the bad spring for a new one.i could do it and i’m not a mechanic.you’ve been conned,is there not an ombudsman or office of fair trading/consumer protection organisation you can have review your bill?we have them in the United Kingdom.
      all the best,

  4. Thanks so much for this helpful article. I have a Hyundai Santafe 2007 which consumes engine oil so fast that the engine oil level drops to “low” at 2,372 Km after service.
    Any info specific to Hyundai would be highly appreciated. Best regards

    • Nothing Hyundai specific, but you’ll want to check to make sure the vehicle isn’t leaking any oil. If you pop the hood, is there a strong oil smell? Common leak points that are not model specific are the valve cover gasket, oil pan, cam seals, and main seals.

      If you are consuming oil this quickly and haven’t noticed a leak, it may be entering the combustion chamber. When you start the car, see if any blue smoke comes out of the exhaust. Blue smoke indicates burning oil.

      You may want to have the radiator checked for hydrocarbons. This may indicate a head gasket failure. A failed head gasket could allow oil to leak into the cooling system, but would likely also be accompanied with overheating issues.

    • I have a Daewoo cielo with G15MF Engine,I noticed the vehicle was lacking power when I engage in gear,it was found that two plugs where being submerged in oil,can this be the problem?

      • It could be, yes. You might want to change plugs, but figure out where that leak is coming from. You may need a new valve cover gasket or something like that.

  5. Nice article very informative about cars and common engine troubleshooting that car owners face once a while… I’m Victor from Nigeria, I drive a ’94 VW Golf MK3 . Its a small yet tough automobile. Anyway, I had it “ringed” couple days back yet it still emits a light ashy colored smoke and the new oil I replaced is all dark on the dipstick and its shorts oil, finally all the pistons except cylinder 2 which is deeply soaked have oil residues on the cylinder heads and the car jerks when in motion prbly cuz of low pressure.

  6. My 2012 Chevy Equinox is using a lot of oil & is involved in a recall that I was unaware of. I’ve passed the 120,000 mile limit on the recall so trying to decide what to do. Can I just keep putting oil in the car to make sure it never runs low or is there any other possible cause for this besides expensive repairs of possible bad valve seals/piston rings? Im going to sell the car soon & it has 121,944 miles on it.

    • There are many possible causes of burning or leaking oil, including bad valve guide seals, bad piston rings, bad front or rear main seals, bad camshaft seals, head gasket leaks, and incorrect oil viscosity, to name a few. It’s impossible to say exactly what is burning oil until you have your vehicle diagnosed at a shop, though.

      Do keep putting oil in it so you don’t ruin the engine, but I’d get the burning oil issue addressed as soon as possible. All that burnt oil is not good for the environment and you may fail a smog test if it persists.

  7. My isuzu elf truck 2007 model 4jj1 engine smokes after idling when you press the petrol pedal and some engine oil leaks around the tarpet cover


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