Six Signs That Your Engine Valve Is Not Working (and How to Test It)

Although engine problems are not something anyone would like to experience, it can occur. A bent engine valve is one of the most troublesome issues that could cause headaches. What symptoms are caused by bent engine valves and what is the severity of this defect?

Considering the engine valves are an essential part of the motor, it’s important to get these problems worked out quickly. Here we will examine the role of the engine and the symptoms that can be caused by a bent valve. This guide will also show you how to check for bent valves. Let’s begin with a quick look at the signs:

A bent engine valve can cause misfiring of the cylinders and a check engine lamp on your dashboard. Other engine problems may be present. If you see low compression with a compression test, it’s also a great sign.

This is a detailed listing of symptoms that indicate a bent valve in your engine.

Índice de Contenido
  1. 6 Bent Engine Valves Symptoms
    1. 1. Verify Engine Light
    2. 2. Engine Reverses
    3. 3. Low compression
    4. 4. Shaking Motor
    5. 5. Manpower shortage
    6. 6. Exceedive oil consumption
  2. What is an Engine Valves?
  3. How to test bent engine valves

6 Bent Engine Valves Symptoms

1. Verify Engine Light

Flashing Check Engine Light

Modern cars continuously monitor every sensor in the car's engine to ensure optimal performance. It will display a check engine light in your dashboard to indicate if anything is amiss with the sensor or parameter.

A check engine light will be lit if any engine valves become bent. To check for air-fuel combination related codes, you can use an OBD2 scanner.

Because engine valves can't be programmed electronically, trouble codes won't indicate that they are bent. But it might mention misfires or the wrong mixture of air and fuel.

2. Engine Reverses


A bent exhaust valve will affect how fumes are expelled from the cylinder. To ensure that the correct amount of pressure remains, exhaust valves must be opened and closed at precisely set times.

The wrong position of an exhaust valve could lead to it being bent. When closed, it can leak or fail to seal correctly. It can also cause an exhaust leak, which affects how fuel is burned. 

If the ECU detects an issue, it may overcompensate and change the fuel delivery to the cylinder. Unburnt fuel can leak into the exhaust if the cylinder is running rich. This could cause a popping or backfire.

3. Low compression

Compression Test

Compression is the pressure inside the cylinder that builds up when the engine runs. A lack of proper valve alignment can lead to imbalanced compression. This pressure can cause problems in the combustion process and make it impossible for the fuel to burn properly.

Because the engine valve is bent, it causes low compression. The seal with the cylinderhead becomes defective because the valve does not close securely. Compression is affected by air and exhaust escaping, which can cause a decrease in power as well as other issues. 

You should check the engine valves if you feel a drop in compression when performing a compression test.

4. Shaking Motor

It is not uncommon for engine valves to become bent and cause engine problems. The motor may shake if a valve becomes damaged due to a broken timing belt. This might be more noticeable when you are driving slower or idling.

You might still be able drive the engine for some time, depending on how damaged your valves are. But, engine failure can occur if the valves are severely damaged. 

5. Manpower shortage

A lack of power is almost guaranteed when there are damaged engine valves. Many times, power issues are caused by reduced pressure within the cylinder. When the valve doesn’t close correctly or sit where it should, the combustion mixture will be thrown off.

Power issues may also be caused by an engine that runs rich in order to correct the problem of the bent valve. It doesn't matter what, the issue must be fixed as it will get more serious over time. 

6. Exceedive oil consumption

To work properly, engine valves need to be lubricated. When the valve moves, its stem is lubricated by oil thanks to the valve seal. The valve seal stops the oil from entering the cylinder.

If the valve bends it is possible to have a worn out or damaged seal. This allows oil to seep through the combustion chamber. The defect can cause excessive oil burning. It can also affect how the engine runs and can damage the catalytic converter if it isn’t fixed quickly. 

A bent engine valve can cause blue smoke to come out of your exhaust pipes. The valve seal may be damaged.

Reported: Six Signs That Your Valve Seal is Bad

What is an Engine Valves?

Engine Valves

The motor's airflow is controlled by the valves. The intake valves can be opened to let air enter the combustion chamber during the intake stroke. To allow the burning of fuel out of the chamber, the exhaust valves are opened during the stroke.

To prevent the ignition of the combustion mixture, the intake and exhaust valves should be kept closed during compression stroke. The combustion force is what gives your car its strength.

The intake and exhaust valves are located inside the cylinder head. Two of each valve are common in most vehicles. A 4-cylinder motor has 16 total valves. However, some LSV8 engines manufactured by GM have only one exhaust and intake valve per cylinder. This gives you a total number of 16 valves. 

How to test bent engine valves

A bent engine valve can be checked by removing the cylinder heads and taking a look at it. This is a lot of work, so the leak down and compression tests can be very useful.

You can see the compression of each cylinder quickly by performing a compression test. It’s a simple way to see how the engine is performing.

The leak down test will be performed if one cylinder shows signs of being low. This will allow you to determine if there is any air leaking from the engine. This leak-down test is connected to the spark plug hole. The crankshaft is turned to the compression stroke. You will hear the exhaust sound. 

If the air is coming from the intake, it’s likely you are dealing with a bent intake valve. The opposite is true for air that comes from the exhaust. This indicates a bent intake valve. The presence of air at these points could be a sign that there has been carbon buildup, which can lead to poor sealing. If you're unsure, a mechanic might perform further diagnostics.

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