What Is Engine Valves : Types, Working, Symptoms, Causes & Replacement Cost

engine valves

Valves are also an extremely important component in internal combustion engines. Many internal parts are used in internal combustion engines. like a piston, rings, valve, crankshaft, camshaft and timing belt or chain. The internal parts of the engine complete the functioning of the engine.

Valves exhaust the exhaust gases of the internal combustion engine and admit pure air from the inlet according to the position and requirements of the piston.

Through this post, we will learn in detail about the valves of the engine. Like, what are engine valves? How do engine valves work? Types of Engine Valves, Symptoms and Causes of Damage Engine Valves and How Much Can Engine Valve Replacement Cost?

What Is An Engine Valves?

Valves are a mechanical component in an internal combustion engine that controls the entry and exit of air and exhaust gases to keep the engine running.

As the engine rotates, the valves open at the correct intervals according to the position of the pistons to allow the engine to breathe and exhaust the gases produced by fuel combustion. Engine valves play a vital role in the internal combustion engine’s ability to function efficiently.

Engine valves are usually made of steel or titanium. The engine valves are fitted into the engine head below the rocker arm of the exhaust camshaft and the rocker arm of the intake camshaft.

Engine valves exhaust the exhaust gases from the internal combustion chamber of the engine according to the position of the piston and intake air into the internal combustion chamber of the engine at the right intervals.

Exhaust Valve

An exhaust valve controls the flow of exhaust gases out of the cylinders in an internal combustion engine. The exhaust valve is usually located in the exhaust compartment of the cylinder head, and the exhaust valve is driven by the engine’s camshaft.

The camshaft lobes push down on the valve stems via the rocker arm, opening the valves in a specific sequence and timing and closing the valves with pressure from the valve spring.

When the engine is running, the exhaust valve is opened during the exhaust stroke via the camshaft lobe and rocker arm, allowing the spent combustion gases from the fuel mixture to exit the cylinder and after the exhaust gases are expelled from the internal combustion chamber of the engine, the exhaust valve closes.

Inlet Valve

The engine inlet valve controls the flow of air and fuel into the engine’s cylinders in an internal combustion engine. The inlet valve is usually located in the cylinder head and is operated by the engine’s camshaft.

The camshaft uses lobes (cams) that push on the valve stems, opening and closing the valves in a specific sequence and timing.

When the engine’s crankshaft is rotated, the inlet valve is opened by pressure from the lobes of the camshaft during the intake stroke of the cylinder, allowing the air and fuel mixture in the engine’s internal combustion chamber to be drawn into the cylinder.

Once the mixture is drawn into the cylinder, the inlet valve closes and the compression stroke begins, starting the fuel combustion process in the engine’s internal combustion chamber.

Inlet valves are usually made of steel or titanium so that they can withstand high temperatures and pressures.

How Do Engine Valves Work?

Engine valves control the intake and exhaust of combustion gases in an internal combustion engine. Engine valves are usually located in the engine’s cylinder head and are operated by the engine’s camshaft and rocker arm.

The camshaft is common in many engines and operates both the exhaust and inlet valves. But in many engines, two separate camshafts are used for these two valves. These two camshafts operate both types of valves separately.

As the engine rotates, the lobes of the camshaft push on the valve stems, causing the lobes of the camshaft to open and close the valves in a specific sequence and timing. When the inlet valve is open, air are drawn into the cylinder.

When the compression stroke begins, both valves close, compressing the mixture. During the power stroke, the spark plug ignites the fuel and air mixture, and the expanded gases push the piston down, turning the crankshaft.

The engine’s exhaust valves open to allow the spent gases from the fuel mixture to exit the cylinders. This process is repeated continuously while the engine is running.

The engine valves also prevent the lubricating oil entering the camshaft and rocker arm in the engine cylinder head from entering the internal combustion chamber of the engine through the valve seals, so as not to disturb the fuel combustion process of the engine.

The valves of the engine are operated according to the speed of the camshaft. The timing belt/chain from the engine crankshaft pulley connects to the camshaft pulley for proper timing to rotate the camshaft.

Thereby, the speed of the camshaft is driven in accordance with the speed of the crankshaft. The engine camshaft opens and closes the valves at the correct intervals according to the position of the pistons in the engine by means of the rocker arm. so that the engine can be started efficiently.

Types Of Engine Valves

The types of valves in an internal combustion engine depend on the design of the engine. Engine valves can be of different types.

1. Poppet Valve

These types of valves are the ones used in normal engines. Common are used in most internal combustion engines. This type of valve consists of a cylindrical stem with a disc-shaped head that sits against a valve seat in the cylinder head.

The valve is opened by the pressure of the camshaft lobe and rocker arm, and the valve is closed by the pressure of the valve spring.

2. Rotary Valve

A rotating mechanism is used instead of pressure to open and close such valves. This type of valve automatically rotates on its axis to open and close a port in the cylinder head, due to which the valve opens and closes.

3. Sleeve Valve

These valves use a cylindrical sleeve that moves up and down within the cylinder head to open and close the ports. The mechanism system of this type of valve is of a different type.

4. Desmodromic Valve

This type of valve uses a mechanical linkage instead of spring pressure to open and close. This allows precise control of valve timing and eliminates valve float at high engine speeds, due to which the valves in the engine can move efficiently.

5. Variable Valve Timing Valve (VVT)

This type of valve uses a mechanical or hydraulic system, rather than spring pressure, to change the opening and closing times. This type of valve uses a hydraulic capsule in the lobe rocker arm of the camshaft to open and close.

This allows for better engine performance and efficiency. Almost at present VVT system is being used in most of the vehicle engines.

Symptoms of Bad Engine Valves

Symptoms of a bad engine valve include decreased engine performance, reduced fuel efficiency, rough idle, misfire, and power degradation. Additionally, abnormal engine sounds, poor acceleration, and increased exhaust emissions are also indicative of faulty engine valves.

Let us know these symptoms of a bad engine valve in detail so that you do not get confused in case of any other engine problem.

1. Loss of Engine Power

If the engine’s valves are worn or the valves are not working properly, the engine cannot draw in enough air and fuel and is unable to exhaust the exhaust gases at the correct timing.

This can result in reduced power and acceleration. For any internal combustion engine to produce power and operate efficiently, the fuel mixture must be successfully ignited in the internal combustion chamber.

2. Engine Backfiring Issue

If the engine’s exhaust valves are not closing properly with the correct timing, exhaust gases can be forced back into the intake system, causing backfiring. Engine backfiring can be a symptom of a damaged engine valve.

3. Low Fuel Efficiency

If the engine valves are damaged and not working properly, the engine is not able to efficiently burn the fuel mixture in the internal combustion chamber, thereby inhibiting the combustion process of the fuel in the internal combustion chamber of the engine. Hence, the engine of the vehicle may reduce fuel efficiency.

4. Knocking or Ticking Noise

When the engine valves are damaged or bent, a strange ticking noise starts coming from the engine while starting it. Because the engine valves are damaged, there is more friction, or the head starts hitting the valve seat.

5. Engine Jerking or Vibration

When the engine valves are damaged, the engine starts vibrating while starting or jerking during acceleration. because damaged engine valves can interrupt fuel combustion in the internal combustion chamber of the engine, due to which the engine starts misfiring, which causes jerks or vibrations.

Causes Of Damaged Engine Valves

  • Engine Valves Breakdown
  • Lack of Lubrication
  • Carbon buildup In Valves
  • Improper Valve Adjustment
  • Engine Overheating
  • Timing Belt Problems
  • Lack of Maintenance

Engine Valves Replacement Cost

Engine valve replacement costs depend on the vehicle model, engine type, and mechanic’s labor costs.

On average, a typical engine valve replacement cost can range from $300 to $2500 or more. These estimated costs will include mechanical labor costs.

Note: If the engine valves cause additional damage to the engine, overhauling the engine is a better option than replacing the engine valves. However, rebuilding the entire engine can be an expensive affair.

FAQ’s

Q. How many engine valves are there?

The valves of the engine depend on the design of the engine. Some engines have two valves for one cylinder (one intake valve and one exhaust valve), and some engines have four valves for one cylinder (two intake and two exhaust valves).

Q. What happens when engine valves fail?

Many engine problems are faced due to the failure of engine valves, such as low engine power, misfires and backfiring, smoke issues, and compression problems.

Q. Where are the 4 valves located?

The valves of the engine are fitted in the valve seat in the center of the engine head. The portion of the head containing the valves is located just above the piston.

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