The crankshaft harmonic balancer is a device connected to the front of an engine’s crankshaft, usually built into the crankshaft pulley. Its purpose is to absorb and reduce harmonic vibrations from the engine as the crankshaft rotates, as harmonic vibrations at high engine speeds can cause accelerated wear and damage to the components. They are usually made of rubber and metal, which easily absorbs any harmonic vibrations that could harm the engine otherwise. Usually a problem with the harmonic balancer will produce a few symptoms that can alert the driver of a potential problem that should be serviced.

1. Engine vibration

One of the first symptoms of a potential problem with the harmonic balancer is engine vibration. The harmonic balancer is specifically designed to absorb harmonic engine vibrations as engine speeds rise. If the harmonic balancer gets too old or fails and can no longer properly absorb the harmonic vibrations, the engine will shake excessively. The shaking will become even more pronounced, and therefore dangerous to the engine at high speeds.

2. Misaligned timing marks

Another symptom of a potential problem with the harmonic balancer is misaligned timing marks. The harmonic balancers found on many vehicles are constructed as two pieces of metal with a rubber layer in between to dampen the vibrations. If the layers separate or slip, the timing marks, which are usually stamped into the front of the pulley, can shift and thus throw off the placement of the timing marks. This will make it difficult, if not impossible to properly time the engine with a timing light.

3. Separated harmonic balancer

Another more serious symptom of a problem with the harmonic balancer is a separated harmonic balancer. If the rubber layer in the harmonic balancer dries or wears out, it can cause the entire harmonic balancer to completely fail by separating. If the harmonic balancer separates, the engine belts will usually come off and the vehicle will be left without engine accessories.

The harmonic balancer is an engine component found on virtually all rotating internal combustion engines and plays an important role in protecting the engine from dangerous harmonic vibrations and potential damage. For this reason, if you suspect that your harmonic balancer may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic. They will be able to determine if the vehicle needs a crankshaft harmonic balancer replacement.

This article originally appeared on as Symptoms of a Bad or Failing Crankshaft Harmonic Balancer and was authored by Ed Ruelas.

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