Table of Contents

Key Takeaways

The following are the key takeaways from this article:

  • The camshaft is an important engine component that assists in opening and closing the valve with the movement of the crankshaft.
  • The important parts of the camshaft include cam-bearing journals, bearing shells, lobes, chain sprockets, thrust plates, and woodruff keys.
  • Some common problems in the camshaft include lobe wear, lifter tapping, backing cylinders, and camshaft popping.
  • Common bad engine camshaft symptoms include engine cylinder misfire, tapping sounds, metal debris in the engine oil, black exhaust smoke, and check engine light.
  • The cost to resolve the camshaft issues can be as low as $50 to replace the faulty bearing and as high as $3000 to replace the faulty camshaft.

Introduction

An internal combustion engine operates when the inlet valve opens, injecting a fuel stream and air into the cylinder through the intake manifold. First, however, the valve must open in synchronization with the crankshaft gear (1).

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Camshaft plays an important role in opening the valves in synchronization with the crankshaft gear. Depending upon the car model, manufacturer, and engine type, different types of camshafts are mounted in the car, such as SOHC, DOHC, etc.
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The automakers use a timing belt to synchronize the motion of the camshaft and crankshaft. This article will shed light on other functions, history, problems, and symptoms of a bad camshaft.

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History of Camshaft

The camshaft is an important part of the engine and was first designed in 1206 by Al Jazari. Al-Jazari employed this part in the water machine, which converts the rotatory motion into straight motion (3). Later in the 8th century, this part was implemented in automotive vehicles. It was found that the crankshaft rotating motion was converted into linear motion with the help of the valve gears (1). The camshaft is present in the internal combustion chamber.

With the evolving technology, the design of the crankshaft has changed, i.e., the size and weight vary, but the function has remained the same.
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Function of Camshaft

The camshaft is the most critical component; its main function is to operate the exhaust valves. The camshaft helps in opening and closing the exhaust valves. The valves in the combustion chamber allow the air and fuel to enter the chamber, and the valves allow the harmful gases to release from the gas chamber. The camshaft detects the requirement of the air and fuel in the chamber (3). Thus, it opens the valve at precise timings, so it can be concluded that the camshaft depends on timings.

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This part of the engine helps maintain the air-to-fuel ratio and releases harmful gases from the engine. Therefore, the crankshaft part is essential and helps maintain the engine’s health.
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Parts of a Camshaft

Although the name camshaft suggests that this component will have two major components cams and a shaft. In reality, a camshaft has certain small components that play an important role in its functioning. Some major parts of the camshaft are briefly discussed below:

Cam Bearing Journals

Cam-bearing journals are used to alleviate cam movement friction and convert its motion. A cam is a rotating component providing oscillating motion to the valves through direct contact.
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With the crankshaft movement, the camshaft rotates, opening and closing the engine valves in a synchronous motion (1). So, cam-bearing journals are used to change the rotary motion to the linear motion of the valves.

Bearing Shells

Camshaft can exert stress on the engine block in case of engine failure. To prevent the breaking of the engine block in engine failure, the automakers have mounted bearing shells on the cams.
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The bearing shells are exactly mounted on the cam bearing journals that help the camshaft rotate smoothly. So, the engine block is prevented from wear and tear using the bearing shells.

Lobes

Another important component of a camshaft is the lobes that work to open/close the valves. For example, the inlet valve opens for air-fuel mixture intake for combustion and closes for the combustion process. Similarly, the exhaust valve opens to exhaust the gases.

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The timing of the opening and closure of the valves is critical for the optimum performance of the engine. So, lobes work with the movement of the piston/crankshaft and ensure that the valves are opened at the right time. Therefore, the speed of the lobe depends upon the engine speed.
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Chain Sprocket

The timing belt is used in the engine to synchronize the camshaft’s motion with the crankshaft’s movement. In addition, a chain sprocket set is attached at the side of the engine, where the crankshaft is located (1).

The purpose of a chain sprocket is to hold the timing belt during the combustion process. With the help of a chain, the camshaft movement is controlled. As a result, the sprockets move at a constant speed even in case of no interaction with each other.
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Thrust Plates

Thrust plates are attached at the engine’s back end to alleviate the play between the camshaft and the timing belt. These plates are mounted on the front side of the engine (5). Some thrust plates are mounted at the backside of the engine to support the rotary cams at the rear of the engine.

Woodruff Key

Woodruff keys are used to retain the cam at the right time.
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A woodruff key is a semi-circular machine shaft that prevents the cams from moving independently. A woodruff key is usually made up of cast iron or cold steel alloys.

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Common Problems in Camshaft

Lobe Wear

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Lobe wear is a common problem that completely impacts the performance of the camshaft in the engine. Lobe wear is a condition that affects the functioning of valves, i.e., they are not opened easily or partially opened.

Due to this error, the oil and fuel are not supplied to the engine on time, and harmful gases are not released. These harmful gases are deposited in the engine walls, and as a result, the efficiency of the engine is impacted (2). In addition, the condition of the lobe wear occurs when the lubrication process is slowed down and oil is not supplied to the camshaft parts (1). Thus, the engine performance is impacted badly, and the engine will fail to accelerate at high rpm. This happens because the valve will only open once a high rpm is supplied. Also, there are chances of misfiring in the engine cylinders, and harsh sound may observe due to the damaged camshaft.

Lifter Tapping

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Lifter tapping is a condition in the engine where the ticking sound is observed from the engine. The lifter tapping in an engine occurs when the camshaft fails to make continuous contact with the lifters.

Lifter tapping may occur for three reasons, i.e., bad oil in the engine, defective lifters, and bent rods in an engine. Overall, this affects the engine’s performance as the damaged rods and the bad engine oil impact the combustion process (5). The air-to-fuel mixture in the engine is disturbed due to the delayed valve opening and closing. As a result, misfires can occur in the engine. This produces ticking noises in an engine, and sluggish behavior of the engine is observed (2). It is determined that the connection between the lifter and camshaft becomes weak when the wrong viscosity oil is used in the engine. If the oil’s viscosity is thick, the oil will not smoothly pass through the valve lifters, and the engine’s rpm is not maintained.

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Another major reason for the tapping in an engine is the bent rod. The main purpose of the engine is the rod is to operate the intake and exhaust valves in the combustion chamber.

The sound is produced when the rod becomes too hard and is unable to move properly. Thus, the performance of the engine becomes poor.

Backfiring and Popping

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The backfiring and the popping sound in the engine are produced due to the defective camshaft. This is because the camshaft’s function is to synchronize the opening and closing of the intake and exhaust valves.

Thus, the gases do not enter the combustion chamber when the camshaft gets damaged. As a result, the air-to-fuel ratio in the engine is delayed, and the spark needs to be ignited on time. This result causes a backfire in the cylinders (2). As a result, the exhaust gases are not released at particular times, and black-colored smoke is released later. This smoke has a rotten egg smell due to the deposition of Sulphur and nitrogen in the combustion chamber. Thus, the engine’s performance becomes poor, and the car cannot accelerate at high speed because the spark’s ignition is delayed. Also, the engine check light is illuminated as a warning signal to avoid accidents later. All these issues occur due to broken camshafts as the valves operating differs due to lack of movement.

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Common Symptoms of a Bad Camshaft

Following are some common symptoms of a bad camshaft:

Engine Cylinder Misfire

As the camshaft plays a role in timing the opening of inlet and outlet valves, a bad camshaft will result in either a lean or rich condition in the cylinder. The cylinder misfire can be noted by a missing engine or an engine providing low power (3). To further analyze the particular misfiring cylinder, you can connect a hand code reader with the OBDII module of your vehicle that will illustrate an OBDII fault code. This can be further decoded to analyze the particular misfiring cylinder.

Loud Tapping Sound

Another symptom of a bad camshaft is a loud tapping sound while driving. The tapping sound may disappear after driving a few miles after the engine components are lubricated. These tapping sounds indicate failure/problems in the lobes. After driving the vehicle for several years, the cam lobes often wear out, resulting in a tapping sound during cam operation. You are recommended to replace the cam lobes at the earliest in case of a tapping sound to avoid any further engine damage.

Metal Debris in the Engine Oil

Another indication of a bad camshaft can be metal debris in the engine oil. When a camshaft malfunctions, metal pieces can be scrapped off the components due to wear and tear. These pieces can be added to the engine oil reservoir (3). Dipping the stick in the engine oil reservoir cannot check the metal debris. However, when draining out the oil, you can analyze the oil for metal debris.

Black Smoke out of Exhaust

Another sign of a bad camshaft is the black smoke from the exhaust tailpipe. It can be due to the rich/lean condition in the engine cylinder due to malfunctioned camshaft movement (4). Black smoke usually indicates that the engine is burning more fuel and requires immediate service before eventual engine damage.

Check Engine Light

Although, the check engine light is an overall indication that some engine component is malfunctioning. You can connect a hand-code reader with the OBDII module to check which engine component is malfunctioning. In case of a camshaft malfunctioning, it is recommended to replace the malfunctioning camshaft component/the camshaft for optimum engine performance.

Common Cost to Resolve Camshaft Problems

The following table illustrates the cost required to resolve camshaft problems:

Common Camshaft ProblemsCost to Resolve Camshaft Problems
Bad Chain Sprocket$50-250 to replace the chain sprocket, $500-1300 to replace the entire timing chain
Wearing out Cams$1500-3000 to replace the camshaft
Bad Camshaft Bearings$50-100 to replace the camshaft bearing
Bad Camshaft Position$200-400 to resolve bad camshaft position

Conclusion

In conclusion, the camshaft functions for the effective opening and closing of the valves. The camshaft comprises several important components, such as bearing journals, bearing shells, chain sprockets, etc. With time, the camshaft components can wear down, or the camshaft position can be disturbed, resulting in bad engine performance. Some symptoms of a bad camshaft include tapping engine sound, metal debris in engine oil, and black smoke out of the exhaust pipe.

FAQs

If the camshaft is malfunctioning, you will hear the tapping, or the check engine light will illuminate the vehicle’s dashboard. In addition, you can check the OBDII code to analyze further whether the camshaft is malfunctioning or some other engine component is performing badly.

Camshaft components wearing and tearing will release metal debris throughout the engine. A driver can analyze the engine oil when it’s drained out. If there are metal pieces in the engine oil, then there is a chance that the camshaft is malfunctioning and the components are wearing.

There is no specified time/mileage after which a camshaft should be replaced. It functions effectively if the engine is serviced properly and a good driver drives the car. However, in some cases, the camshaft malfunctions that should be replaced immediately to avoid further engine damage.

References

About Author

Andrew Ray

Andrew is an automotive technician with 10 years of experience mainly in American and Japanese cars, covering everything from routine vehicle maintenance and engine inspections to tire rotation.