Burnt Valve 101: Inspect Symptoms, Causes & Fix (With Cost)

By September 24, 2022Common Questions

Valves may get burnt in high-temperature conditions. Symptoms of burnt valves include poor power, engine misfiring, increased fuel consumption, and rough idling. Your car’s valve is a core part of the engine’s working process. It helps regulate airflow into and out of the cylinder, which is critical to ignition. 

Personally, I have experienced burnt valves, and the first thing I noticed was that my engine power dropped unexpectedly. It was followed by a clicking sound from the engine system, difficulty in starting, and engine misfiring. At that point, I knew something was wrong and immediately got the valves replaced. 


7 Common Symptoms Of Burnt Valves

1. Engine Misfire

Burnt valves cause engine misfire.

When your engine has a burnt seal, the engine will misfire because the air and fuel compression will escape quickly. One of the significant duties of the valve is to seal the engine cylinder properly to allow the engine to adequately mix fuel and air and create the needed compression for the engine, which will then be converted into the power to drive the car.

Once the valve is burnt, the engine will not have the right amount of air-fuel mixture, which makes ignition very difficult. The engine’s combustion area will begin to underperform, and your engine will not get the power it needs to run the car. 

2. Difficulty in Starting Engine

Burnt valves can cause difficulty in starting engine.

Another common symptom of a burnt valve is a bad engine start. It will take several cranking to get your engine to start. The engine depends significantly on the compression created by the mixture of air and fuel. Once the compression escapes, it will be difficult for the engine system to create an ignition. The engine will require more fuel and air mixture to replace the escaping ones before ignition can happen. 

3. Rough Idling 

The valve also serves as a secure medium for the engine, as it contains a safety plunger. This safety plunger protects the engine from a backfire that can get into the crankcase. Once there is a bad or burnt valve, the valve plunger can get damaged and serve as obstruction of airflow.  If the burnt valve is not replaced fast enough, oil vapor and other forms of dirt can build up in the valve, which can drastically reduce airflow and cause your engine to have a rough idle. 

4. Increased Fuel Consumption

Burnt valves cause increased fuel consumption.

Fuel consumption is eminent when you have an engine with a bad or burnt valve. A bad valve means a leaking compression. The engine needs to make up for the compression leaking through the valve. It then releases more fuel into the engine combustion system to compensate for the escaping compression. In situations like this, your engine will have bad fuel consumption. 

5. Triggered Engine Light 

Burnt valves can cause check engine light.

The engine light means that the Powertrain Control Module (PCM) has spotted a problem with the engine system. When your engine’s valve is bad, something is wrong with the engine system, and the PCM can detect it. The PCM can detect these problems by using various sensors in the engine system; these sensors communicate with the PCM and notify it when something is wrong.  The PCM could also easily pick up other symptoms caused by faulty valves, like engine misfire, which could trigger the check engine light. 

6. Reduce Power 

A burnt valve can reduce the power the engine can generate for the use of the vehicle. Once the valve gets damaged, it can not hold in enough compression to be used by the engine. The amount of compression or pressure present in the engine will determine the amount of power the engine will be able to create.  A burnt valve will drop the compression drastically by allowing it to escape. Once the compression escapes, then the engine will not be able to generate much power. 

7. Noise from Valve 

A burnt or damaged valve will make noises because it no longer functions well. Although other causes like low oil level can cause noise from the valve, sound from the valve is a common way to know that your valve is bad. The noise could be a ticking or a clicking sound. 


How Do You Inspect an Engine Valve?

There are two major ways to inspect the valve of your engine, and it may require that you either remove the valves or not. Removing the valve from your engine could be tedious and require professional assistance, which will cost you more.

To inspect your valve without removing it, you will need some essential tools to get started. Below are the tools that you will be needing:

  1. Wrench and Ratchet 
  2. Socket 
  3. Spark Plug Socket 
  4. Compressor tester

Below is a step-by-step guide to getting the inspection done by removing the valve. 

  1. Before you start the process, it is vital to ensure that the engine does not start during the procedure. You can do this by disconnecting the spark plug wires. 
  2. Also, proceed to remove the spark plug. 
  3. Connect the compressor tester to the position your spark or glow plug used to be using an adapter or socket. 
  4. You will have to crank your engine to start the procedure, and a friend can do this while you perform the inspection. 
  5. Proceed to accelerate a couple of times 
  6. If the compressor tester reads individual lower figures or multiple lower figures, your engine has low compression, which could result from a burnt valve.

You will need more heavy-duty tools to inspect the valve by taking it off. To perform this procedure, you will have to disassemble the cylinder head to be able to get to the valve. Once the valve has been taken out, then you can examine the valve for burns, cracks, or any other form of damage. 

Common Causes Of Burnt (Or Damaged) Valves

There are a lot of factors that could cause your valve to get damaged. Some of them include the working temperature of your engine, poorly seated valve, and poor air or fuel mixture in the engine combustion system. Generally, the cause of your burnt valve could be traced to the condition in which the engine is being used and maintained. 

Below are some of the common causes of burnt valves.

1. High Working Temperature 

The most common cause of burnt valves is the high temperature in the engine system. High temperature can be caused by many factors, including a failing cooling system. The cooling system is the aspect of the engine that ensures that the engine’s temperature is regulated. 

The coolant system includes the coolant fluid and water pump. Once the engine is low on coolants or water, then there is a high probability that your engine’s valve could get burnt. You must check the coolants and water level regularly to avoid a burnt valve or other damage to the engine. 

2. Poorly installed valve 

Another common cause of a burnt valve is one that is not sitting well on the valve seat. It could be caused by poor installation of the valve and rusted valve seat, among others. A valve not sitting right could cause hot air to escape through the valve and cause it to burn. 

3. Engine Running Lean 

When your engine is running lean, it means the mixture of air and fuel in the engine is inaccurate. The engine may receive more fuel than air and could be the other way around. Condition like this can cause the engine to run at a very high temperature which could cause the engine’s valve to burn.  A significant cause of this problem is issues with the fuel pump or oxygen sensor. Once these parts are damaged, it could affect the air and fuel ratio. 


What Happens When Engine Valves Burnt & Fail?

When the engine valve gets burnt and fails, your engine’s cylinder will no longer function properly, and compression will easily escape. It will ultimately lead to a loss of power coupled with other symptoms. A valve is a crucial tool in the engine’s internal combustion system. What the valve does is that it controls the level of compression in the engine system. This compression is what the engine converts into needed power for the vehicle. 

When the valve gets burnt, then the compression in the engine will no longer be regulated. The valve will also no longer be able to seal the compression properly. The compression will then escape through the cylinder area. Once this happens, the engine power will drop, and the engine will not perform as it should.  If not repaired immediately, a burnt valve could lead to more underlying issues in the future.  


Can You Drive With a Burnt Valve?

You can drive with a burnt, but driving without repairing the problem is not advisable. You will experience some difficulty and discomfort when driving, making the driving experience less enjoyable. 

When you have a burnt valve, your engine will no longer be able to create the power it needs. Although your engine may start, which could be very difficult and take several cranking, the driving experience is not that great. If you do get your engine to start, then your engine may stall or not pick up acceleration like it used to. 

You will also experience some unusual sounds coming from the engine. It is your engine showing you something is wrong and to be fixed. Nothing is more embarrassing than a noisy engine system.  The valves are crucial parts of the engine system and play crucial roles; once it is damaged, you should visit a mechanic immediately and should avoid driving your vehicle. The burnt valve could escalate and cause more severe issues in the engine. 

How Much Does a Valve Job Cost?

Valve jobs will cost you between $900 to $2000 to replace your engine’s valves. Your engine makes use of more than one valve. A cylinder can use between two to four-valve, depending on the type of engine you are using. Each valve will cost you between $100 and $200.

The cost of repairing your valve varies due to many factors. Some of the factors may include the type of engine your vehicle is using. Some engines make use of more valves per cylinder than other engines. Some engines make use of two valves per cylinder, that is, one valve for the intake and one for the exhaust. In contrast, others use as many as four valves per cylinder, two for the intake and the others for the exhaust. 

The reason some engines make use of more valves than others is to better optimize the ratio of fuel and air mixture. By doing this engine can get more power and better performance than those using two valves per cylinder. 

Another factor that could influence the price of changing your valve is whether you will be repairing it yourself or not. Employing a professional to do the replacement could be very expensive because the replacement procedure is very tasking and could take a lot of time. Getting a professional mechanic is the best option despite the price that comes with it because you will be sure of the best job done on your replacement. 


How Much Does It Cost to Replace Valves and Pistons?

Replacing the valves and pistons on your engine system will cost you between $1,500 and $3,000. The reason the price of the replacement is this high is that the job is challenging and could be time-consuming. The repair could take a day to two days to get done.

Replacing the piston and the valve includes removing all cylinders to get to the valve and piston rings. The task is quite tiring and requires heavy-duty tools. Replacement like this needs a professional and can not be done by an amateur. Doing the replacement without being a professional mechanic could lead you to damage the engine further. 

It would be best to know that replacing the valve and piston could be more expensive and cost as much as $5,000. The price could be influenced by the number of cylinders your engine has. Engine cylinders could range from four, six, to eight. If you have eight cylinders, you can expect your replacement to be more costly if you replace all valves and pistons.  Piston rings are not as expensive as valves and will cost you about $100 per piston ring. Valves could cost as much as $200. The price depends on the brand and quality of the part you buy. Make sure to use a trusted mechanic certified by the appropriate body during the replacement process. 


Can Engine Valves Be Repaired Without Replacement?

Valves should not be repaired when damaged; you should replace them to avoid damaging your engine.

The valves must be replaced when damaged due to burns, wearing out, or other mechanical damages. Repairing them will no longer be possible, and if you push to repair them, it could cause severe damage to the engine system. A repaired valve system could cause particles to enter the combustion system, leading to engine failure. 

You can push for repair when the valve problem is caused by dirt; then, you can proceed to clean your valve. Replacing the valve could be very expensive, but it is worth doing. Having to replace the valve is way better than fixing a severe engine issue and still have to replace the valves.   



Q: What Is Included in a Valve Job?

A valve job is work done on either or all the cylinders and internal combustion area. The reason for doing this is to improve the surface of the poppet valves and the valve seats of both the intake and exhaust valves. Doing this will improve the engine’s performance by giving a better fuel and air ratio. The job is done when the seats of the valves are worn out.  Having a valve on the engine includes cutting the top, bottom, and sometimes, the secondary cut of the valve seats.    


Q: How Long Do Engine Valves Last?

There is no direct answer to how long a valve could last, but how long your valve will last depends on the working condition of your engine. If your engine is maintained correctly and in good working condition, expect a long-lasting valve. Eventually, your valve will need replacement, but it is expected to give you long-lasting use.


Q: Can You Lap a Burnt Valve?

You can lap the sit of your burnt valve, but you must ensure that the valve is replaced. It is advisable not to reuse or repair a burnt valve. Repairing a burnt valve could cause severe problems to your engine system, which will cost even more to repair.

Ifandi L.

Ifandi L.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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