Symptoms of a Bad Harmonic Balancer：

Engine Vibrations：

The harmonic balancer’s job is to dampen vibrations applied to the crankshaft. As a result, when the balancer fails, you may feel a significant vibration from the engine compartment.

Noticeable Harmonic Balancer Wobble：

When the rubber isolator begins to deteriorate, the balancer usually begins to separate, creating a noticeable wobble when the engine is running.

Unusual Noises：

A faulty balancer can result in a knocking, rattling, or squeaking sound that corresponds with engine speed. In some cases, the noise is bad enough to be mistaken for an internal engine problem.

Also, a balancer that’s beginning to fail can cause abnormal movement from the drive belt or automatic drive belt tensioner, resulting in clicking or squealing noises when the engine is running.

Illuminated Check Engine Light:

Your car’s primary computer, which is often referred to as the powertrain control module (PCM), relies on a crankshaft position (CKP) sensor signal to determine crankshaft position and speed.

The CKP sensor reads a toothed or notched wheel that’s usually located on the crankshaft or harmonic balancer. If the harmonic balancer fails, it can cause the sensor to create an abnormal signal, prompting the PCM to turn on the check engine light.

Visible Wear or Damage:

If you take a look at the harmonic balancer, you might be able to see visible wear or damage. For example, the rubber insulator may have deteriorated, resulting in a separation between the hub and outer portion of the balancer.