What causes burnt valves?

Burnt valves (mostly associated with exhaust valves) are a condition of engine valves ineffective in providing a tight seal between the valve seat and the valve. The burnt valve condition affects the exhaust valves exposed to hot engine gases and parts, and as a result, the valves get damaged.

Although not on all occasions, the burnt valve condition also affects the intake valves. In most cases, a burnt valve may have a worn-out gap along its edges that causes exhaust gases to escape past the sealing of the valve. 

Besides, wear-out of the valves is caused by excess heat exposure from the hot engine gases; what other causes of burnt valves? The common causes of burnt valves are; 

  • lean running of the engine
  • a prolonged LPG kit fitting that causes fewer valves lubrication, 
  • and insufficient cooling causing the engine to overheat. 

Common causes of burnt valves

1. How lean running of the engine causes burn valves

An engine running lean is a condition that affects most cars’ engines and results from too low air to fuel or fuel-air mixture. In other words, where there is much air mixing with little fuel, the engine’s ignition chamber will be receiving much air and less fuel, and vice versa for ignition.

In most cases, engine running lean suggests several cars’ significant problems. The common causes of an engine running lean are fuel injectors failures or damages, dirty MAF sensors, and failed oxygen sensors.

Lean mixtures are identified as burning with high temperatures compared to normal air-fuel mixtures. Therefore, the nearby engine parts to the combustion chamber, including exhaust valves, are exposed to intense heat.

If the exhaust valves have no valve guide, they are burnt out; hence the lean mixtures in the engine cause a burnt valve.

2. How a prolonged use of LPG kit fitting causes burnt valves

Installation of LPG systems in a car plays a crucial role in prolonging engine life. In this technique, several ideas are used, such as fitting a new ECU, and LPG tank, and modifications in the manifold.

The primary use of the LPG idea is to allow the car to use two sources of fuel, petrol or diesel. Fuel conversion through LPG prevents the engine from pre-ignition or knocking since it works on over 100 octanes. 

In this system, LPG, the engine parts are exposed to burning cleaner, as any dirt resulting from computation is cleaned up. However, the cleaning can go up to reach the exhaust valve’s lubrication. As a result, the lubrication in these valves goes low, and excess heat causes the valves to be burnt, hence burnt valves.

3. How insufficient cooling causes the engine to overheat and lead to burnt valves

Your car engine is designed to work heavy tasks to operate your car’s main components. Therefore, the engine gets hot and needs effective cooling. If the engine lacks enough cooling, it gets hotter over time and burns around components, including exhaust valves.

As a result, the exhaust valves are turned into burnt valves.

Symptoms of A Burned Valve

  • Engine performances go down: The burnt valves may develop holes that leak out all gases; therefore, the engine will have low gas for compression. Where there is less compression in the engine, the engine’s performance lowers.
  • Causes of misfiring: This results due to the engine cylinder failing to discharge efficiently.
  • Difficulties when starting the car: All parts should play their role correctly for the vehicle to function effectively. If the car has a burnt valve, it will experience difficulties when starting.

Can you drive with a burnt valve?

Yes, you can drive with a burnt valve, but you will be doing more damage to the car’s internal parts. If you continue driving while the valves are burnt, you will be damaging your engine. So, the best thing here is to avoid driving your car with burnt valves and wait until you repair or replace them.

Driving with burnt valves will lead to a misfire which will in turn cause havoc to the catalytic converter. Since a catalytic converter is a critical emission device, damaging it can make it break apart inside. This will eventually lead to closing up the exhaust hence a more severe power loss making the car difficult to drive. 

It is therefore advisable to fix the burnt valves before driving or cease operating with burnt valves. 

How long can I drive on a burnt valve?

While there is no specific answer to this, you should only drive your car on a burnt valve only for emergency or temporary uses. If you go for a long distance, you will be causing more damage, which might cost you a lot in the long run. For instance, if the burnt valve breaks, the cost of repairs will be higher.

Therefore, although you can drive on a burnt valve, you shouldn’t do so for longer distances. And let the drive be just an emergency like when moving to the garage or mechanic. Otherwise, you should consider replacing or regarding a burnt valve before driving. 

Can an exhaust leak cause a burnt valve?

Yes, the primary cause of burnt valves is exhaust leaks. If the valve is not sealing correctly, it will result in a burnt valve. An exhaust leak is caused by low back pressure in the system, allowing the unburnt one to move past the valve. 

Therefore, ineffective seals between the valve seat and the valve. In most cases, burnt valves happen when the valve cannot seal correctly after the damage of the valve material due to high temperatures. 

Can a burnt valve be fixed?

A burnt valve can be fixed by an experienced mechanic only if the damage is minor, thus, depending on the severity of the burnt. When a valve is burnt, it becomes ineffective, and there is no way it can be fixed.

You can replace a burnt valve by removing the head cylinder and replacing the damaged conditioned parts or new ones. However, repairing or replacing depends on how badly it is burnt. Minor burns can require a fix, but major one requires a replacement. 

How much does it cost to replace a valve?

A car is an expensive investment, meaning that even its parts are costly. The repair costs for a burnt valve differ depending on the mechanic shop you visit and any other parts affected. Repair costs include service costs and the resources needed. 

Generally, the cost for the required repair resources ranges from around $25 to $60. The pricing for valve adjustment ranges from approximately $250 – $350. Paying the mechanic can cost about $200 to $300 depending on where you will go. 

Therefore, in estimation, the overall cost of replacing a burnt valve is about $2000. The final price you will get for replacing the valve will depend on the car, taxes, and reinstallation materials.

Video Overview


Valves can burn for several reasons, including the usual wear and tear. When a valve is burnt, it might lead to cylinder misfires and smoke in the exhaust. While you can fix this, you can only do so for minor damages, but major ones only need a repair.

However, going for a repair can be costly, but it is vital as it will prevent damage caused by driving a car with a burnt engine.

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