Top 10 Symptoms Of A Bad Crankshaft Pulley & Replacement Cost

The crankshaft pulley, also referred to as the vibration damper or harmonic balancer, is a critical part of the engine’s crankshaft system. This pulley is responsible for providing power to several key parts within your vehicle’s engine. When the crankshaft pulley goes bad, it produces different signs. This article explains the bad crankshaft pulley symptoms, causes, and how to replace it.

 What is a Crankshaft Pulley?

The main function of the crankshaft pulley is to transfer power from the crankshaft to different engine accessories like the water pump, the air conditioning compressor, the power steering pump, and the alternator. The power transfer is accomplished through the drive belt, enabling these accessories to fulfill their individual tasks.

Crankshaft Pulley

The crankshaft pulley of your engine is directly attached to the crankshaft. The external rim of this pulley has a grooved design that helps to hold the engine belts. These belts are employed to drive different accessories including the air conditioning compressor, power steering pump, water pump, and alternator.

Aluminum is commonly used to construct crankshaft pulleys. But some vehicles also have a cast iron design instead. 

The pulley also acts as a harmonic balancer. It helps to reduce engine vibration, improving the life of the engine’s main bearings. It accomplishes this by absorbing the torsional vibrations that the crankshaft may produce as part of its rotation.

The crankshaft pulley comprises two distinct parts: the inner ring, which is connected to the crankshaft, and the outer ring which is connected to the inner ring. The inner ring has different weights designed to neutralize vibrations, while the outer ring, constructed from a rubber material, absorbs any remaining vibrations.

Symptoms Of a Bad Crankshaft Pulley

If the crankshaft pulley becomes faulty, it may result in a variety of issues such as an inconsistent engine idle, hard to start the vehicle, a stalling engine, and increased engine vibration. Moreover, it may prevent the battery from charging effectively and cause the engine to overheat. In extreme cases, it can even contribute to transmission damage.

The following are the most common symptoms of a bad crankshaft pulley:

1) Engine Vibration

A vibrating engine is one of the clear symptoms of a bad crankshaft pulley.

Engine Vibration, symptoms of bad crankshaft pulley

If you neglect the performance of your vehicle, a faulty crankshaft pulley may produce intense vibrations coursing through the car.

Because this pulley is directly connected to the harmonic balancer—a device that absorbs engine shocks—when it fails, there is nothing to dampen these vibrations. Consequently, the severity of the shaking escalates over time.

2) Loss Of Power Steering 

The crankshaft pulley drives the steering pump via a serpentine belt. The steering pump circulates hydraulic fluid throughout the steering system, assisting you in steering the car.

Loss Of Power Steering

If the serpentine belt fails to drive the steering pump, you’ll lose this supplementary steering assistance. In such conditions, it will be challenging to turn the vehicle, potentially resulting in loss of control.

However, there are many other reasons for a hard steering wheel such as insufficient power steering fluid or steering rack.

Read More: Why Steering Wheel is Hard To Turn?

3) Car Won’t Start

When the crankshaft sensor of your vehicle doesn’t accurately gauge the speed of the engine using the teeth of the crankshaft pulley, you might experience difficulties starting the engine.

engine wont start

Additionally, such a situation could result from a depleted car battery due to a malfunctioning alternator. However, usually, you would observe some battery-related problems before it reaches this point.

4) Rough Idle

Even under normal operations, the crankshaft pulley is subjected to significant strain. When it goes bad, it disrupts the balance of the entire system.

Rough Idle, signs of bad crankshaft pulley

You might observe an uneven idle as a consequence of the crankshaft pulley failure. There are chances that your crankshaft sensor is unable to accurately read the engine speed from the faulty crankshaft pulley, resulting in a rough engine idle.

Read More: Rough Idle Symptoms and Causes

5) Bad Alternator

When the crankshaft pulley malfunctions, it may result in the alternator either undercharging or overcharging the battery. This irregular charging may cause early battery failure and amplified deterioration of the electrical system.

Faulty Alternator

As we discussed above, the crankshaft pulley drives the alternator. Therefore, when this pulley goes bad, your headlights may start to blink, or the interior lights are less bright. If you observe any of these signs, it’s crucial to get your car checked by a certified mechanic.

6) Stalling Engine

Your engine may be stalled due to a bad crankshaft pulley. However, this symptom is not common. If the pulley is unable to spin the serpentine belt, maintaining the operation of the engine becomes a challenge.

Engine Stalling

Certain vehicle models use a crankshaft position sensor to measure engine speed based on the teeth of the crankshaft pulley. When the pulley becomes faulty, the engine may stall.

However, this symptom appears after all other symptoms. For instance, there would need to be significant vibration for the serpentine belt to be dislodged in the first place. Ideally, you will need to address the issue before it escalates to such a degree.

7) Overheating Engine

An overheated engine is one of the clear symptoms of a bad crankshaft pulley. If your vehicle’s crankshaft pulley is unable to turn the serpentine belt, the water pump might cease to operate. The water pump plays a crucial role to ensure the normal operating temperature of the engine.

car Overheating

Ignoring an overheating engine is something you should never do. If left unchecked, this can lead to severe engine damage, such as a cracked cylinder head or a blown head gasket, both of which would necessitate costly repair.

Read More: Engine Overheating Causes

8) Transmission issues

If your crankshaft pulley or harmonic balancer isn’t working right, it can cause problems with your car’s transmission system. This could make your transmission slip or not work as it should, which can make your car use more fuel and wear out the transmission faster.

Transmission Slipping, Symptoms Of a Bad harmonic balancer

You might notice problems like your car taking longer to shift gears, shifting gears roughly, or gears slipping. However, some other reasons may also lead to transmission issues.  So, if you see them, it’s vital to get your car checked out by a professional mechanic.

Read More: Causes of Transmission Slipping 

9) Unusual Engine Noise

Unusual engine noise is also a symptom of a faulty crankshaft pulley or harmonic balancer.

Grinding Noise due to bad crankshaft pulley

If you detect grinding or squealing sounds while the engine is running, it might suggest a failure in the harmonic balancer. Typically, these sounds are most perceptible as you start the engine or it’s working hard, like when you’re accelerating from a standstill.

The belt driving the crankshaft pulley could also slip or become loose if the pulley is compromised. This could result in a squealing noise too.

10) Misaligned Belts

Misaligned Belts

A failing pulley can also cause the engine belts to become misaligned. This may cause the belts to squeak or squeal, and they may wear out more quickly than usual.

Causes of the Bad Crankshaft Pulley

  • Manufacturing defects
  • Physical impact due to an accident 
  • Engine vibrations
  • Issues with the belt tensioner or the serpentine belt
  • Wrong installation
  • Wear and Tear

Crankshaft Pulley Location

Crankshaft Pulley location

The crankshaft pulley is positioned at the crankshaft end. It has a wheel-like shape and features a groove that matches up with the key in the crankshaft. This pulley houses the harmonic balancer, equipped with assorted weights intended to dampen vibrations.

How to Replace a Crankshaft Pulley

Follow the below-given steps to replace or check the crankshaft pulley:

  • First, park your car on a level ground.
  • Find the crankshaft pulley. It is recommended to check your vehicle’s service manual to exactly find the location of the crankshaft pulley.
  • Now, disconnect the drive belt. You can do this by loosening the tensioner pulley bolts and sliding the belt off the pulley. Remember the path of this belt so you can reassemble it accurately at its place.
  • Next, attach a socket to the bolt installed on the crankshaft pulley. You also need to confirm that the socket is the right size for this bolt.
  • Attach a cheater bar to the end of the socket. A cheater bar is a long piece of metal that provides additional leverage when attempting to loosen a tight bolt.
  • Rotate the cheater bar in the same direction the engine rotates, which is typically anticlockwise.
  • Brace the cheater bar against a sturdy piece of metal to give you leverage when rotating the cheater bar.
  • Insert your key into the ignition switch and rotate it. This action will turn the crankshaft pulley, helping to loosen it.
  • Once loose, finish unscrewing the bolt by hand to avoid damaging it.
  • Remove the crankshaft pulley by using a crankshaft puller. This tool helps you remove the harmonic balancers and other pulleys from crankshafts without causing harm.
  • To install the new crankshaft pulley, reverse the steps you’ve followed so far. Ensure that the bolt is tightened according to the owner’s manual instructions.
  • Reinstall the drive belt, making sure it goes around all pulleys and is tensioned as per the manufacturer’s manual.
  • Lastly, turn on your engine and inspect for a leak.

Crankshaft Pulley Replacement Cost

The replacement cost of the crankshaft pulley and harmonic balancer replacement is not a costly job. You may need to invest about $140 to $670 for parts and labor. If you perform this job yourself, you will need to just pay for the parts that may only cost $20 to $420.

FAQ Section

How long can a Harmonic Balancer last?

Typically, a harmonic balancer should not fail before reaching 50,000 miles. However, if it’s not functioning as it should, it could lead to significant engine damage in a relatively short period.

Can I drive with a bad crankshaft pulley?

When the crankshaft pulley goes bad, it’s advisable to cease driving. Persisting in driving with a faulty crankshaft pulley may escalate to more severe issues, or even result in the vehicle breaking down due to overheating or failure to start.

Can a crankshaft pulley come loose by itself?

Yes, it is possible for the crankshaft pulley to loosen even when the bolts are properly torqued. This can occur as a result of prolonged vibrations in that specific area of the engine. If this issue isn’t addressed promptly, it could lead to serious complications.

Can a bad pulley make a knocking noise?

Yes, a faulty harmonic balancer may create a knocking noise. However, this noise may also be produced due to some other issues. If you detect knocking while driving, it might be attributable to worn-out bearings, an unbalanced air-fuel mixture, using the wrong fuel, poor timing, or a faulty tensioner. Hence, a thorough inspection is essential to identify the main issue.

What happens when your crankshaft pulley goes bad?

A malfunctioning crankshaft pulley has the potential to result in the failure of both the alternator and power steering pump. This can be evident in symptoms such as a depleted car battery and loss of power steering functionality.

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