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

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 working, symptoms, and causes of a bad rocker arm.

What is a Rocker Arm?

In the context of an IC engine, a rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake/exhaust valve.

Rocker arm

Rocker arms used in automobiles are typically made from stamped steel or aluminum in higher-revving applications. Some rocker arms (called roller rockers) include a bearing at the contact point to reduce wear and friction at the contact point.

Rocker arms are typically located between the pushrod and intake and exhaust valves. They are pushed and pulled by pushrods to “rock” up and down, opening and closing the exhaust valve and intake valve of the combustion chamber on engines with a camshaft below the engine.

Pushrods move up and down as the camshaft below them rotates, driven by the crankshaft. In this way, power can flow from the combustion chamber of the engine through various parts to the wheels to put the vehicle in motion.

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.

With broken or loose rocker arms, the exhaust valves and intake valves can’t function correctly, and the cylinder associated with the faulty rocker arm will be disabled. This will ultimately limit the performance of your engine and your ability to drive the car smoothly and safely.

 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.

Working of Rocker Arm

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.

A roller rocker arm is a type of rocker arm that contains needle bearings at the point of contact between the valve and the rocker arm, rather than metal sliding on metal. This decreases uneven wear friction and “bell-mouthing” of the valve guide. These may also be used for engines with overhead camshafts.

Types of Rocker Arms

The rocker arm has the following major types:

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

1) Stamped Steel Rocker Arms

Stamped steel rocker arms are probably the most common types of rocker Arms. They are the easiest and cheapest to manufacture because they are stamped from one piece of metal. 

Stamped Steel Rocker Arm

They use a trunnion pivot that holds the rocker in position with a nut that has a rounded bottom. This is a very simple way of holding the rocker in place while allowing it to pivot up and down.  

2) Shaft Rocker Arms

The Shaft Rocker Arms build off of the Full Roller Rocker Arms. They have a shaft that goes through the rocker arms. Sometimes the shaft only goes through 2 rocker arms, and sometimes the shaft will go through all of the rocker arms, depending on how the head was manufactured.

Shaft Rocker Arm

The reason for using a shaft is for rigidity. Putting a shaft through the rocker arms is much more rigid than just using a stud from the head. The more rigid the valve train, the less the valve train deflection and the less chance for uncontrolled valve train motion at higher RPM.

3) Full Roller Rocker Arms

The Full Roller Rocker Arm is not a stamped steel rocker. They are either machined steel or aluminum. They replace the trunnion pivot with bearings. These rocker arms still have the stud from the trunnion pivot, but they don’t use the nut.

Full Roller Rocker Arm

They have a very short shaft with bearings on each end (inside the rocker), and the shaft is bolted securely in place, and the bearings allow the rocker to pivot.

4) Roller-Tipped Rocker Arms

These rocker arms are very similar to 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.

Roller Tipped Rocker Arm

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

Symptoms of a Bad 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.

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

  1. Misfiring
  2. Clicking noise
  3. Physical deterioration
  4. Reduction in performance
  5. Check engine light illumination

1) Misfiring 

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.

Read More: Causes and Symptoms of Engine Misfiring  

2) Clicking Noise

A worn rocker arm might be the problem if you hear a clicking or ticking noise when you start your engine. There are also various other reasons that a clicking or ticking noise might be occurring. Once you’ve ruled out any external causes, you can start worrying about internal issues like a broken rocker arm.

If you hear a clicking or ticking noise and suspect a broken rocker arm listen to see if the noise is coming from the top of the engine. If it’s a V-shaped engine, the noise will only be coming from one side.

Once you’ve identified the location of the ticking or clicking noise, the only way to verify that it’s a broken rocker arm is to tear apart the engine’s top end and look at what’s going on.

3) Physical Deterioration

Visual inspection of the rocker arms can also reveal any cracks or wear. After removing the valve cover, look for pieces of metal below the rocker arms, as they can grind on the pivot point and valves when they are in poor condition.

Degraded rocker arms should be replaced even if no other symptoms are present because problems will soon follow.

4) 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.

5) Check Engine Light Illumination

There are tons of sensors monitoring your engine’s performance. Everything gets checked and verified for proper function. So, while there’s no sensor for each rocker arm, the decreased engine performance can easily lead to a check engine light.

The exact code on that light will vary because the broken or worn rocker arm’s side effect tripped it, not the rocker arm itself. That’s not to say that the code won’t mention a rocker arm, it definitely can, but it might point you toward an actuator or a switch when that’s not necessarily the problem (but it could be!).

Read More: Causes of Check Engine Light Flashing 

Causes of a bad Rocker Arm

  • Bad fuel injectors or fuel that isn’t compatible with your car. Fuel problems will always cause your engine to misfire.
  • One of the major causes of a bad rocker arm is bad manufacturing. This includes all effects that increase brittleness or those inducing cracks and or stress raisers in the component. Improper heat treatment has been considered a major cause of many failures in the literature.
  • Bent or broken valves cause the valves to stay open. Bent valves, in turn, are caused by bad engine timing.
  • Continuous use of contaminated oil or the wrong type of oil. This is why it is recommended to change oils at specific periods with the right types of oil.
  • Engine overheating is probably caused by faulty radiators or other factors.
  • Driving long miles, especially when the engines are not maintained. However, servicing your car regularly and using the right types of oil can make the rocker arms last.
  • Bad timing belt or chain. A faulty timing belt stops the engine from igniting and turning over. When this happens, the rocker arms, valves, and even the pushrods get damaged.

Read More: Causes of bad Engine Control Unit

How to replace a faulty Rocker Arm

You can fix or repair a rocker arm yourself or have a professional do it. To do this, first, remove the faulty rocker arm. Then, replace it with a new one. But before you start, ensure that your tools box and work light are close by. Follow the below-given steps to replace or install a rocker arm:

  • Open your car’s engine cavity; locate the negative battery cord, and disconnect it.
  • Remove the cover from the assembly of the air cleaner and pop out the air
  • Get a socket and ratchet; use them to remove the nuts. Then raise the assembly from the engine
  • Tag each spark plug cable with a marker and masking tape. Please take note of each plug’s location.
  • Hold the spark plug cable at the end and remove each cable from the spark plug
  • Clear all wires from your workspace and path
  • Separate the throttle cords from the throttle body
  • Remove the wire stand from the input plenum and set it aside
  • Take out the bolts from the valve’s cap
  • Take out the valve’s cap from the head of the cylinder
  • Remove nuts from the damaged rocker arms.
  • Loosen the camshaft
  • Take off the rocker arms
  • Place the new rocker arms and torque the nuts
  • Torque the camshaft
  • Place the valve’s cap over the new gasket
  • Install and tighten the bolts
  • Install the throttle cord stand to input space and tighten it
  • Attach the throttle wires to the body of the throttle.
  • Plug the spark cables to the right spark according to the tag you placed when taking them off
  • Push each cable until they fall into the position
  • Attach the spark plug cables to the clips
  • Put the air cleaner on the engine and tighten the nuts with a wrench. Attach the negative battery wires. Then, use a wrench to fix the nut.

Rocker Arm Repair and Replacement Cost

The average single-rocker arm replacement cost is from $450 to $1,600 – and almost all of this cost is for labor. In fact, each rocker arm part typically costs between $6 to $25. But that’s not the only parts you’ll need.

Because to reach the rocker arms, you’ll need to remove the valve covers and various other components, so you should replace all the gaskets associated with them too. You’ll also end up draining the oil, so you should also throw a filter in there.

But even with all those factors thrown in, parts should only cost you around $90 to $160 – all the rest is labor costs. That’s a large part of the reason you should replace all of your rocker arms at the same time.

They tend to wear out at a similar rate, and since most of the work the mechanic already did most of the work by accessing the rocker arms, throwing in a few extra rocker arms doesn’t cost you another $500 to $1,500 each. As long as they’re under the same valve cover, you’re probably only looking at an extra $8 to $26 for each additional rocker arm.

If you have to remove the other valve cover gasket to reach the additional rocker arms (like in a V-shaped engine), this cost will be slightly higher, but it’s still worth the initial investment to save you some money down the road.

Rocker Arm Location

The rocker arms are located at the engine head, connecting the camshaft to the exhaust and intake valves.

When you look at your engine, you’re not going to see the rocker arms. That’s because they’re underneath the valve covers that are positioned directly over the engine’s heads. Furthermore, they’re located directly between the engine’s pushrods and the intake and exhaust valves.

While it’s easy to point to where a rocker arm is, actually seeing and accessing the rocker arms is far more complicated.

FAQ Section

What is a Rocker ratio?

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

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.

How do you tighten Rocker Arms?

To tighten your loosed rocker arms, simply performs the following steps:

  • Start the engine
  • Remove nuts until your engine starts clicking
  • Slowly tighten the nuts until the clicking stops
  • Tighten again, but this time in a quarter(¼) turns
  • Do them one after the other until you tighten all the loosed rocker arms.

Can I drive with a broken rocker arm?

It is not recommended to drive with broken rocker arms. In case of broken or loose rocker arms, the exhaust valves and intake valves can’t function correctly, and the cylinder associated with the faulty rocker arm will be disabled. This will ultimately limit the performance of your engine and your ability to drive the car smoothly and safely.

How many rocker arms are in a V6?

A V6 engine has 6 cylinders with two rocker arms on each cylinder. In a nutshell, a V6 has a total of 12 rocker arms.

What happens when a rocker arm fails?

As the rocker arm goes bad, it limits the function of your exhaust and intake valve. Due to this, the exhaust and intake valves don’t work efficiently, and they also disable the function of the corresponding cylinders. This will ultimately limit the performance of your engine and your ability to drive the car smoothly and safely.

What are the symptoms of a faulty rocker arm?

As the rocker arms go bad, they give one of the below-given symptoms:

  1. Engine misfires
  2. Stalling issues
  3. Check engine light illumination
  4. Reduction in performance
  5. Clicking noise from the engine
  6. Physical deterioration
  7. Poor fuel economy

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