Troubleshoot Engine

Is It Bad To Drive With Bad Valve Seals?

Can you drive with bad valve seals

Bad valve seals in a car will cause a variety of engine problems like decreased performance, oil leaks, and increased emissions. But can you do any long term damage if you continue to run a car with bad valve seals?

The answer is yes, driving with bad valve seals will cause further damage to your engine and other components such as the spark plugs, pistons, catalytic converter and oxygen sensors and this will most likely lead to costly repairs in the future.

While it may be tempting to continue driving with bad valve seals to avoid the cost of repairing them, it is important to address the issue as soon as possible to prevent further damage to your vehicle.

In the following sections, we will explore the symptoms of bad valve seals, the potential consequences of driving with them, and the best ways to address the issue.

Can You Drive with Bad Valve Seals?

Driving with bad valve seals is not generally a good idea, but most engines will continue to run even if the valves are leaking and are not making a tight seal with the engine block.

Valve stem seals are small seals that are found on the intake and exhaust valves of an engine. They are designed to prevent oil from entering the engine cylinder from the cylinder head.

Valve stem seals are usually made of rubber or a similar material and are located at the top of the valve stem, where it enters the valve guide. The valve stem seal sits on the valve stem and forms a tight seal with the valve guide.

They allow the valve to be lubricated and operated by the engine oil without the oil passing the valve and getting into the engine combustion chamber.

Valve seals on valves
Valve seals allow valves to form a tight seal when closed

Valve stem seals are important because if they fail, they can allow oil to be burned along with the fuel. This can cause a number of problems, including increased emissions, reduced engine performance, and increased oil consumption.

Additionally, if oil is allowed to build up in the combustion chamber, it can cause deposits to form on the valves heads and spark plugs, which can lead to further engine problems.

Valve stem seals can wear out over time due to exposure to heat and engine oil, and may need to be replaced.

One of the most common symptoms of bad valve seals is blue or gray smoke coming from the exhaust. This is caused by oil burning in the combustion chamber and being expelled through the exhaust system.

If left unchecked, this can lead to further damage to the engine, including clogged catalytic converters and damaged spark plugs.

So, while it is possible to drive with bad valve seals, it is not recommended. The longer you drive with bad valve seals, the more damage can be caused to the engine.

What Causes Bad Valve Seals?

Over time, valve seals tend to wear out or become damaged, leaving them unable to form a tight seal when the valve is closed

One of the main causes of bad valve seals is actually normal wear and tear. As an engine ages, the seals can become brittle and lose their ability to seal properly. This can allow oil to seep into the combustion chamber, leading to excessive smoke and oil consumption.

Another common cause of bad valve seals is overheating. When an engine overheats, it can cause the seals to become brittle and crack. This can cause a variety of problems, including reduced engine performance and increased emissions.

In some cases, bad valve seals can also be caused by improper installation. If the seals are not installed correctly or if they are damaged during installation, they may not be able to seal properly, leading to oil leaks and other issues.

It’s also important to properly maintain the seals through regular engine servicing. If an engine is not properly maintained, it can lead to a variety of problems, including worn out seals. Regular oil changes and other routine maintenance can help prevent these issues and prolong the life of the valve seals and the engine.

Can Low Tire Pressure Cause Damage to Valve Seals While Driving?

Low tire pressure can potentially cause damage to valve seals while driving. It’s crucial to check and maintain proper tire pressure to prevent potential issues. Following safety and performance tips will ensure your vehicle’s overall health and safety on the road.

Symptoms of Bad Valve Seals

When valve seals start to fail, they usually cause several telltale symptoms that can affect the engine’s performance and lifespan.

Here are some of the most common symptoms of bad valve seals:

Symptom 1. Blue smoke from the exhaust pipe

One of the most common symptoms of bad valve seals is blue smoke coming from the exhaust pipe.

When valve stem seals are worn, they can allow oil to seep into the combustion chamber and mix with the fuel. This oil and fuel mixture then burns and produces blue smoke that is visible when it leaves the engine via the exhaust pipe.

The blue smoke is typically most noticeable when the engine is started or when the throttle is first opened after idling for a period of time.

This is because engine valves operate under oil pressure. So when the engine is off or idling, the oil collects in the combustion chamber, and then burns off when the engine is started or the throttle is opened.

Symptoms 2. Oil On The Spark Plugs

Another sign of bad valve seals is oil on the spark plugs.

Worn valve stem seals can let oil seep into the engine cylinder and this can collect on the spark plugs. This oil can cause the spark plugs to become fouled, which can reduce engine performance and cause misfires.

It’s worth noting that oil on spark plugs can also be caused by other engine problems, such as worn piston rings or a faulty cylinder head gasket. Whatever the cause, if you notice oil on your spark plugs it is important to figure out the cause to prevent further damage to the engine.

Symptom 3. Increased oil consumption

If you notice that your car is burning more oil than usual, this could also be a sign of bad valve seals.

If the valve stem seals are worn and leaking, they can allow oil to seep into the combustion chamber and this will be burned along with the fuel. This can cause the engine to burn more oil than it normally would, leading to increased oil consumption.

Worn valve stem seals can also cause oil to collect inside the engine cylinder on the spark plugs and around the piston crown. This can lead to fouling of the spark plugs, localised damage to the pistons reduced engine performance, and increased oil consumption.

Symptom 4. Rough Engine Idling

Another common symptom of bad valve seals is rough engine idling. This can be felt as vibrations or shaking when the car is stopped.

The rough idling occurs because the oil that has seeped into the combustion chamber and has mixed with the fuel. This oil and fuel mixture can cause the engine to run poorly, leading to rough idling.

Also, as explained earlier, worn valve stem seals can cause oil to collect in the combustion chamber and on the spark plugs. This can lead to fouling of the spark plugs, reduced engine performance, and rough idling.

One final way that bad valve stem seals can cause rough engine idling is by causing a vacuum leak. When valve stem seals are worn, they can allow air to enter the sealed engine cylinder, which can cause a vacuum leak and a subsequent loss of pressure. This can lead to rough idling and other engine performance issues.

Symptom 5. Poor acceleration

You may also notice a lack of power or slower acceleration when driving with bad valve seals. Oil leaking into the engine cylinder will mix with the fuel and will contaminate the inside of the cylinder. The oily fuel mixture will not burn as efficiently as it should and this will affect the engine performance.

If there is damage to the spark plugs or if there is a vacuum leak, this will further compound the problem and will also result in poor acceleration.

What Happens If You Drive With Bad Valve Seals?

Driving with bad valve seals will usually have a lead to a range of consequences, some of which can be quite serious for your engine.

  1. Increased Oil Consumption: One of the most common symptoms of bad valve seals is increased oil consumption. This is because the seals are no longer able to prevent oil from seeping into the combustion chamber, where it is burned along with fuel. Over time, this can lead to a significant drop in oil levels, which can cause engine damage if not addressed.
  2. Poor Engine Performance: When oil is burned along with fuel, it can create a range of issues that can negatively impact engine performance. For example, it can cause misfires, reduce power output, and make the engine run rough or stall altogether.
  3. Damage to the Catalytic Converter: If left untreated, bad valve seals can cause oil to accumulate in the catalytic converter, where it can clog the system and cause significant damage. This can be an expensive problem to fix, as catalytic converters can cost upwards of $1,000 to replace.
  4. Increased Emissions: Burning oil can also increase the amount of harmful emissions that your vehicle produces. This can cause your car to fail emissions tests and can also be harmful to the environment.
  5. Engine Damage: In severe cases, driving with bad valve seals can cause significant engine damage. For example, if oil levels drop too low, the engine may overheat, which can cause the pistons to seize and the engine to fail.

What Next – How to Diagnose and Fix Bad Valve Seals

When it comes to diagnosing bad valve seals, there are a few signs to look out for. The most common symptom is blue smoke coming from the exhaust pipe after idling or when first accelerating.

Its important to determine when the blue smoke is coming from the exhaust, as continuous blue smoke when driving can indicate worn piston rings instead.

Damaged piston rings
Damaged piston rings can also cause blue smoke

With worn valve seals you may also notice oil on the spark plugs when you inspect them. Here are a few other things to check before you dismantle the engine entirely.

  1. Check for blue smoke from the exhaust: One of the most common symptoms of bad valve stem seals is blue smoke coming from the exhaust. This is caused by oil leaking into the combustion chamber and being burned along with the fuel. If you notice blue smoke coming from your exhaust, it is a strong indication that your valve stem seals may be worn.
  2. Check for oil consumption: Another symptom of bad valve stem seals is increased oil consumption. If you notice that your vehicle is burning more oil than usual or you have to add oil more frequently than before, it is possible that your valve stem seals are worn.
  3. Carry out a compression test: A compression test can help determine if your valve stem seals are leaking. This test measures the pressure in each cylinder when the engine is turned over. If there is a significant difference in pressure between cylinders, it may indicate that the valve stem seals are leaking.
  4. Inspect the spark plugs: Worn valve stem seals can cause oil to collect on the spark plugs, leading to fouling and reduced engine performance. If you notice oil on your spark plugs, it may be an indication that your valve stem seals are worn.
  5. Listen for unusual engine sounds: Worn valve stem seals can cause the engine to run poorly and make unusual sounds, such as ticking or tapping noises. If you notice any unusual sounds coming from your engine, it is possible that your valve stem seals are worn.

If you suspect the problem is in fact worn valve seals then the best way to permanently fix the problem is to replace them altogether.

This will require removing the cylinder head and valve train, which can be a time-consuming and difficult process if you don’t have the right tools and experience. It is usually a good idea to leave this sort of job to a professional, but bear in mind it is an expensive fix.

If you want a temporary fix then you can try a high-quality oil additive that can help to soften and condition the seals. This can sometimes help to reduce oil consumption and improve engine performance in the short term.

Another option is to use a thicker oil. This can help to reduce the amount of oil that leaks past the valve seals and into the combustion chamber. However, it’s important to note that using thicker oil can also reduce engine performance and fuel efficiency.

Some more expensive synthetic engine oils have additives that can help to improve worn valve seals. Check with your user handbook to see if there is a different engine oil that you can try as it may help to reduce valve leaks temporarily.

About the author

The Motor Guy

The Motor Guy is a passionate car enthusiast with a love for troubleshooting and diagnosing all sorts of vehicle problems.

With years of experience in OBD diagnostics, he has become an expert in identifying and solving complex automotive issues.

Through TheMotorGuy.com, he shares his knowledge and expertise with others, providing valuable insights and tips on how to keep your vehicle running smoothly.

Qualifications:
- 12 years experience in the automotive industry
- ASE Master Automobile Technician
- A Series: Automobile and Light Truck Certification, A9 Light Vehicle Diesel Engine Certification
- Bachelor's Degree in Information Systems

2 Comments

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  • Is it safe to drive my car to the mechanic if I’m noticing blue smoke from the exhaust, or should I get it towed instead?

  • I’ve noticed my car burning more oil than usual and there’s been blue smoke from the exhaust when I start it. Could this indicate that the valve seals in my engine might be bad, and if so, what are the first steps I should take to address it?