Vibration Balancer

Step by step guide on how an automotive engine harmonic balancer works, this information pertains to most vehicles.

Step 1 - A harmonic balancer is used to help smooth the operation of the engine while running. This added weight is used to give momentum to the engine crankshaft which is subject to uneven thrusts caused by the combustion process.

Harmonic Balancer (Center Bolt Removed)

Step 2 - When a balancer fails a puller is needed to remove the unit for replacement.

Harmonic Balancer Puller

Step 3 - The balancer features the sealing surface the front crankshaft seal rides against, which spins while the engine is in operation while controlling engine oil from leaking externally.

Front Main Seal Surface

Step 4 - When a vibration damper fails the outer metal ring will separate from the main hub causing a ringing sound. The balancer featured bellow has lost the rubber insulator allowing complete separation, once this condition has occurred the balancer must be replaced.

Failed Harmonic Balancer

Step 5
- A installer tool is used to help push the damper back onto the crankshaft, using a hammer will damage the thrust bearing of the engine and is not recommended.

Harmonic Balancer Installer

Helpful Information

A harmonic balancer or vibration damper is connected to the front of the engine crankshaft and is designed to help reduce vibration. The harmonic balancer is comprised of two separate pieces, the first is a mass which is bolted to the crankshaft and the second is the energy dissipating element which are separated by a rubber insulator. The rotating mass is designed to absorb vibration created from the crankshaft while the engine is in operation. Almost all engine are equipped with a harmonic balancer. Due to the stress and strain that is placed upon the harmonic balancer the unit can sometimes crack or separate. If the front main seal fails it will cause an oil leak which can only be replaced by removing the balancer.

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Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-12-08)