Harmonic Balancer



I had a air conditioner belt break. The mechanic was asked to replace both belts (I had 59000.+ miles, so thought it would be prudent). Paid &180.00. 10 miles later…

BOTH Belts BROKE! Now, they say it was a bad Harmonic Balancer! ($400.00 more!) Should they have not seen it was bad while replacing both belts? (2004 Subaru…no trouble until now). Signed, Broke in Ohio.


Unless the harmonic balancer is so badly damaged that it’s obvious, installing belts doesn’t include inspecting the harmonic balancer as a normal practice.



As far as I recall, Subaru engines DO NOT have harmonic balancers.
Harmonic balancers are necessary with most inline 4-cylinder engines, due to their inherent imbalance. However, the horizontally-opposed layout of the Subaru engine cancels virtually all harmonic vibration.

If I were you, I would ask this mechanic to show you the harmonic balancer on this engine. If he says that it is internal, then ask him to open his shop manual and show you where it refers to a harmonic balancer on this engine. Unless my memory is playing tricks with me, he will be unable to show you a harmonic balancer on this engine.

I think that you are being “hosed” by an incompetent/unscrupulous mechanic.
After verifying my (possibly incorrect) recollections regarding the absence of a harmonic balancer, perhaps a phrase like, “I will have my attorney contact you”, might motivate him to perform the needed repairs without charge.


Subies do have harmonic balancers. http://www.partstrain.com/ShopByDepartment/Harmonic_Balancer/Subaru

Harmonic balancers actually disspate rotational vibrations (or pulsations, if you will) caused by the impulses on the crankshaft as the combustion impulses happen, rather than lateral or resonant vibrations. Typically they’ll simply be rubber piece between the crankshaft and and the pulley that stores some of the rotational energy from the crankshaft and releases it back to the crankshaft out of phase with the combustion pulses. Sort of the same principle as a “sound cancelling system” that you’d use on an airplace.

A bad harmonic damper can destroy the belts, and I agree with Tester that unless it’s so bad that it’s wobbling it would not necessarily be detected during a simple belt change.


My error!
I was thinking of the Second Order Balancer, or whatever Honda calls the balance shafts on their 4-cylinder engines.


“Harmonic Balancer” is really a misnomer. It should be called a torsional vibration damper.