Pattern Failure: Crankshaft Pulley
By Phil Coconis/autoMedia.com
Many manufacturers use a crankshaft pulley with a two-piece design, consisting of the central "hub," an outer "drive ring," and a high-density rubber composite "absorption layer" sandwiched in between. Variations of this design have been in use for decades with great reliability. It's not uncommon to see original equipment pulleys still in service on '60s-era vehicles.
The nature of the failure of the pulley design considered in this article has to do with a loss of adhesion between the rubber absorption layer and the outer ring, hub, or both. In other words, the outer ring, which turns the belt driving the engine's accessory pulleys, slips in relation to the inner ring.
This slippage can sometimes result in a misalignment between the two, which will cause the pulley to visibly "wobble" with the engine running. It can also cause a constant slip, while the pulley appears to be turning straight and true.
As you can probably imagine, all sorts of trouble would result under such a condition, from low charging system output, to poor and inconsistent power steering assist and air conditioning operation, as well as higher cooling system operating temperatures. Not to mention operating noise.
I have actually seen such pronounced slippage that, after removal, I could induce it while holding the pulley in my hands. That's even more amazing when you consider that the unit was still turning concentrically while mounted on the engine!
At any rate, replacement of the pulley on this model is fairly straightforward, requiring no special tools—although a half-inch drive impact gun is helpful for removal of the pulley bolt, and a proper torque wrench is helpful for correctly securing it.
Follow the procedure outlined in the service manual, observing all safety precautions, especially relating to raising and supporting the front of the car. With the right front wheel and splash shield removed, you can see how accessible the pulley is.
This is not uncommon for all makes, especially where early failure of the original part is involved. So it seems that car companies do learn from their mistakes—or at least their pattern failures.