Jim Grant's Tech Tips
'90 Chevy Lumina APV, Belt Tensioner vs. Harmonic Balancer
Q:
How do you know when
something is wrong with the harmonic balancer vs something wrong with
the tensioner in a '90 Chevy Lumina APV when there is a loud knocking
when it is turned on. It can drive back and forth but I never leave the
engine running for more than one or two minutes.
A:
I would suggest removing
the serpentine belt and starting the engine. If the automatic belt tensioner
is the cause for the noise the only noise you will hear is that of the
engine. If the harmonic balancer is failing you will hear a noise. You
may want to snap the throttle a time or two as well. Why? Without the
load created by the serpentine belt and the accessories that it drives
the harmonic balancer will tend to quiet down a bit. The throttle snap
(quick acceleration and release of the throttle) causes the balancer to
work, resulting in a noise if failing. With the serpentine belt removed
you'll get a good idea of which path you'll need to follow to condemn
the offending component.
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