5 Symptoms of a Bad Crankshaft Harmonic Balancer & Replacement Cost

Crankshaft Harmonic Balancer

With so many working parts on and around the engine, it can sometimes be difficult figuring out what part is going bad, as many symptoms relate to multiple components. That’s the case when you have a bad crankshaft pulley or a bad crankshaft harmonic balancer. 

We review the symptoms of a bad crankshaft pulley to help you narrow down if this part is causing you trouble. 

Symptoms of a Bad Crankshaft Pulley

  1. Engine Vibration
  2. Irregular Engine Idle
  3. Dead Alternator
  4. Failure of Power Steering Pump
  5. Damaged Transmission

Engine Vibration

Car Vibrates On Idle

The most prominent symptom that something is wrong with the crankshaft pulley is engine vibration. This will be the first sign you notice, as long as you are paying attention. 

The crankshaft pulley is often equipped with a harmonic balancer. This component absorbs vibration from the engine, allowing you to accelerate smoothly. However, when the balancer fails, vibrations are no longer absorbed. 

This defect causes noticeable shaking that gets worse the faster you go. 

Irregular Engine Idle

Low Idle Rpm

As you sit in your vehicle parked, you become familiar with the sound of the idle. When something seems off, it could be related to your crankshaft pulley. 

Irregular engine RPMs are common with a bad crankshaft pulley because the dampener is put under more pressure, especially while idling. You might notice that the engine RPMs fluctuate all over the place. 

Dead Alternator

Battery Alternator Light

While the alternator charges the battery and runs accessories, the crankshaft pulley is responsible for supplying power to this component. If the crankshaft pulley fails, the alternator no longer turn and produce power. 

You will notice signs that look like you have a dead car battery. The lights might flicker and you won’t be able to start the vehicle for long since the battery can’t be charged. 

RELATED: 8 Causes of a Car Battery Light On While Driving

Failure of Power Steering Pump

Power Steering Pump On Table

The car’s power steering pump is also powered up by the crankshaft pulley. This vital component pumps hydraulic fluid into the system so your steering works the way it should.

When the power steering fails, it will require much more effort to control your vehicle. You might think that the system is low on fluid, but a simple check will show that’s not the case. 

Damaged Transmission or Internal Engine Parts

Transmission Gears

If you allow the engine vibration to occur long-term, it will lead to transmission or internal engine damage. It can wear out the crankshaft bearings if you are unlucky, and your car’s transmission has a lot of parts that aren’t made to handle that type of vibration. The gears, input shaft and bearings are all susceptible to damage.

When the transmission starts to fail, you might notice trouble shifting, whining sounds and leaking fluid. This is not something you want to deal with simply because you had a bad crankshaft pulley. 

Crankshaft Pulley Function

Crankshaft Pulley

The car engine operates from the power given to it from the fuel. Then, this power is delivered to other components through the use of various electrical and mechanical systems. One of these mechanical systems is the crankshaft pulley, which is responsible for power distribution.

The crankshaft pulley powers all of the components connected to the crankshaft. While the crankshaft will drive the car wheels, the pulley transmits power to other parts, such as the alternator and power steering pump.

The crankshaft pulley includes an internal dampener, responsible for decreasing vibrations running along the pulley belts. If left unchecked, these vibrations can cause damage to the systems that are connected. 

While a torn or defective crankshaft pulley belt is simple to replace, a broken dampener requires a crankshaft pulley replacement. 

So, what causes a crankshaft pulley to go bad? Even though the part is designed to last the lifetime of your engine, it can fail easily. Most models have a rubber isolation ring that breaks down when exposed to high temperatures, which happens naturally because of the engine. Plus, if there is a coolant or oil leak that gets on the pulley, it can contaminate it and speed up deterioration. 

Crankshaft Pulley Location

Crankshaft Pulley Location

The crankshaft pulley, otherwise known as a harmonic balancer, is found on the end of the crankshaft. It’s a wheel-shaped device with grooves that connect directly onto the crankshaft. 

While the crankshaft is responsible for converting straight or linear movement to the pistons, the crankshaft pulley connects to several other components through the use of accessory belts. 

Crankshaft Pulley Replacement Cost

The crankshaft pulley replacement cost is between $350 and $400, depending on the car model and labor costs. You could spend $200 to $240 for a new crankshaft pulley, plus about $150 for labor.

If you purchase an aftermarket crankshaft pulley, you could save yourself a little money. Additionally, luxury cars might cost slightly more overall. 

If you wanted to replace the crankshaft pulley yourself, the job isn’t that complicated. 

  1. Remove all of the engine drive belts.
  2. Take off the crankshaft pulley bolt. You will need a pulley holder and a high torque impact wrench.
  3. Remove the old pulley.
  4. Install the new crankshaft pulley.
  5. Put the bolt back on and tighten it.
  6. Re-install all of the engine drive belts. 
Written by: Magnus Sellén

Founder, owner & main author of Mechanic Base. I have been repairing cars for more than 10 years, specialized in advanced diagnostics & troubleshooting. I have also been a drifting driver and mechanic for over 7 years.