What is Rocker Arm? | Symptoms and Causes of bad Rocker Arm

The vehicles are most commonly used all over the world. The vehicle consists of different components such as an engine, sway bar, rocker arm, etc. The rocker arm is a component that transmits the camshaft motion to the engine’s exhaust and intake valves. This action occurs in response to wave motion by direct contact of these components to the tappet according to the shaft movement. This article mainly explains the various aspects of the rocker arm.

What is a Rocker arm?

In an IC engine, the rocker arm is a mechanical device that transmits the pushrod motion to the corresponding exhaust and intake valves.

Stamped steel or aluminum (for high-speed applications) is most commonly used for the construction of rocker arms. Some types of rocker arms also contain a bearing at the contact points to decrease friction and wear at the contact points.

The rocker arm is usually located between the intake valve and exhaust valve, and pushrod. This pushrod uses to push and pull the arm. This pushing movement of the pushrod “rocks” the rocker arm upward and downward; due to that, it opens and closes the intake and exhaust valves of the engine combustor with a camshaft under the engine.

A camshaft is connected to the crankshaft. The camshaft gets power from the crankshaft. As the camshaft receives motion from the crankshaft, it moves the pushrod moves upward and downward. The pushrod further transfers its motion to the exhaust and inlet valves through the rocker arm.

The proper opening and closing of the exhaust and inlet valves ensure the proper supply of fuel to the engine. Ultimately, the fuel burns into the combustion chamber, and power generates. This generated power is transferred to different parts of the engine that run the vehicle.

If the rocker arm is cracked or loose, the exhaust and intake valves don’t work properly, and the cylinder linked with the damaged rocker arm will be disabled. This will highly affect the engine performance.

Working of Rocker Arm

A rocker arm is part of the engine that ensures the proper fuel supply to the engine. One end of the rocker arm is connected to the pushrod.

rocker arm working

As the crankshaft rotates, it transfers rotary motion to the camshaft. When the camshaft receives power, it pushes the pushrod upward. The top of the pushrod pushes on the side of the rocker arm and turns the arm. This rotation presses the other end of the rocker arm down on the top of the valve, moving the valve down to open.

When the outside of the valve is permitted to return due to camshaft rotation, the inside rises, allowing the valve to shut.

Read More: Working of Crankshaft 

What is a Rocker ratio?

Rocker arm ratio is a ratio between the distance traveled by the valve and the distance traveled by the push rod effectively.

The rocker ratio may be calculated by the ratio of the distance from the pivot point of the rocker arm to the point where it joins the camshaft/pushrod and the point where it joins the valve contact point. When the rocker ratio is greater than 1, the camshaft lift increases significantly.

Types of Rocker Arms

The rocker arm has the following major types:

  1. Stamped steel rocker arm
  2. Roller tipped rocker arm
  3. Full roller rocker arm
  4. Shaft rocker arm

1) Stamped Steel Rocker Arms

It is one of the most famous types of rocker arms. These rocker arms have an easy design because they are stamped from a single metal piece. They have low cost than other rocker arms.

Stamped Steel Rocker Arm

The stamped steel rocker arm uses a trunnion pivot with a round bottom nut that fixes the rocker in place. This is an easy and simple method to keep the rocker in its position as you rotate it upward and downward.

2) Roller Tipped Rocker Arms

These rocker arms are very similar to the stamped steel rocker arms. They have a roller on the end tip of the rocker valve. This design generates less friction, less valve tip wear, and higher performance.

For simplicity, this rocker arm contains trunnion bolts and nuts. They are made of cast or machined aluminum or steel.

Roller Tipped Rocker Arm

3) Full Roller Rocker Arms

It is not a stamped steel rocker. It is made by the machining of aluminum or steel. It contains bearings instead of a trunnion pivot.  

Full Roller Rocker Arm

The full roller rocker may also utilize studs for the trunnion pivot but not nuts. It contains a short shaft. This shaft contains a bearing on each side. The shaft is screwed tightly in its position, and the bearing permits the rocker arm to rotate.

4) Shaft Rocker Arms

It consists of a full roller rocker arm. It has a shaft that penetrates the rocker arm. According to the design of the cylinder head, the shaft can only go through two rockers or through all rockers. This shaft is used because of its rigidity.

The stiffer the valve train, the lower the valve train deflection, and the less likely it is that the valve train motion will go out of control at high speed.

Shaft Rocker Arm

Symptoms of a Bad Rocker Arm

The efficient working of the rocker arm is very important for the efficient working of the vehicle. The main function of the rocker arm is to transfer the camshaft motion to the exhaust and inlet valves and ensure the proper opening and closing of the inlet and exhaust valves.

As the rocker arm goes bad, the vehicle generates one of the following signs:

  1. Clicking or Ticking Noises
  2. Misfiring or Stalling
  3. Drop in Performance
  4. Check Engine Light On
  5. Physical Deterioration

1) Clicking Noise

The ticking or clicking noise is one of the main symptoms of a bad or worn rocker arm. The vehicle may generate ticking or clicking noises due to many other reasons. This ticking or clicking noise is an external sign. When you ignore the external symptoms of a problem, it may lead to different internal issues such as cracked rocker arms.

As the rocker arm is damaged, the engine generates clicking noises that come out from the top of the engine. In V engines, the noise is only generated from one side.

Once you’ve identified that you have a broken rocker arm, you must replace it as soon as possible to prevent an expensive repair.

2) Misfiring or Stalling

The rocker arm controls the opening and closing timing of the inlet and exhaust valves. It handles how long each intake valve and the exhaust valve open. It ensures the proper supply of fuel to the engine combustion chamber.

As the rocker goes bad, it can’t deliver a sufficient supply of fuel to the engine, which causes misfiring.  

3) Reduction in Performance

The rocker arms also help to ensure the efficient working of the engine. As the rocker goes bad, you will see a reduction in the engine performance. In such conditions, the engine couldn’t run the vehicle according to the requirements.

4) Check Engine Light Illumination

There are many sensors that monitor engine performance. These sensors check and verify the proper working of the engine. Each rocker arm doesn’t have a sensor, but if engine performance drops, a check engine light starts illuminating.

The exact code for this light is different as it may activate due to the side effects of a worn or damaged rocker arm. That doesn’t mean that the code doesn’t mention the rocker, yes, but it may point you to an actuator or switch if that’s not an important issue.

Read More: Causes of Engine Check Light Flashing 

5) Physical Deterioration

If you notice that you have a faulty rocker arm, you must immediately visually inspect it. You can easily find a bad rocker through visual inspection. With the valve cover off, look for a piece of metal under the rocker arm. These metal parts can wear out if the pivots or valves are bad.

If your rocker arms are damaged, you must replace them immediately.  

Read More: Signs of bad Crankshaft Position Sensor

Causes of a bad Rocker Arm

  1. Bad Fuel Injectors: Defective injectors incompatible with the vehicle are the most common causes of bad rocker arms.
  2. Contaminated Fuel: Old or contaminated fuel is one of the most common causes of a bad rocker arm. A contaminated or insufficient fuel supply may stop the engine from working.
  3. Bad Manufacturing: The bad manufacturing of rocker arms is one the most common factors of their failure. This comprises any effects that cause cracks and increased stresses in the assembly. In the literature, improper heat treatment is believed to be the primary cause of maximum failures.
  4. Damaged Valves: If the engine valve is damaged, it will remain open. Most commonly, poor engine timing damages the valves.
  5. Contaminated Oil: Old or contaminated oil may also cause bad rocker arms. Your vehicle must have sufficient and clean engine oil to work the rocker arms efficiently.
  6. Engine Overheating: Engine overheating is one of the most dangerous things that you must avoid. It may damage different parts of the vehicle or cause complete engine failure. Different factors lead to engine overheating, including a bad radiator or insufficient coolant.
  7. Damaged Timing Chain or Belt: A bad timing belt can prevent the engine from starting or turning. This can damage rocker arms, push rods, and valves.

Read More: How to change Engine Oil?

Where is Rocker Arm Located?

The rocker arm is located in between the pushrod and the exhaust and intake valves. The pushrod connects the rocker to the camshaft. This pushrod takes motion by the camshaft and pushes the rocker arms.

As the rocker arm gets motion by the pushrod, it opens and closes the exhaust and inlet valves. The proper working of the rocker ensures the proper supply of fuel to the engine.

Rocker Arm Repair and Replacement Cost

The rocker arm replacement or repair cost varies according to your local labor cost, type of vehicle, and brand of the rocker arm. The average single-rocker arm replacement cost is between $440 to $1,700. Almost all of the money mentioned here is spent on labor. In fact, swingarm parts typically range from $7 to $22. But that’s not all you need.

FAQ Section

What is the function of the rocker arm?

The main function of the rocker arm is to transfer the camshaft motion to the exhaust and inlet valves and ensure the proper opening and closing of the inlet and exhaust valves.

What happens when a rocker arm fails?

As the rocker arm fails, it can’t properly open and closes the intake and exhaust valves. When the inlet and exhaust valves don’t open and close properly, they can’t properly supply fuel to the engine. The broken or damaged rocker arms reduce the engine performance and generate many other problems.

What are the types of rocker arms?

The rocker arms have the following major types:

  1. Stamped steel rocker arm
  2. Shaft rocker arm
  3. Full roller rocker arm
  4. Roller tipped rocker arm

What are symtpoms of bad rocker arms?

As one of the rocker arms go bad, it gives one of the below-given symptoms:

  1. You will notice a poor fuel economy
  2. Your vehicle may start misfiring
  3. Stalling issues
  4. Poor performance of your vehicle
  5. Physical deterioration
  6. Check engine light illumination
  7. Clicking noise from the engine

Can you drive with a broken rocker arm?

Driving with rocker arms is not very dangerous. If your vehicle’s rocker arm is cracked or loose, the intake and exhaust valves will not work properly, disabling the cylinder associated with the damaged rocker arm. Eventually, this limits engine performance and limits the vehicle’s ability to drive smoothly and safely.

Read More
  1. Different types of Engines
  2. Types of External Combustion Engine
  3. Causes and Symptoms of Engine Overheating
  4. Symptoms and causes of bad Oil Control Valve

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