Over numerous hours of operation factors such
as contamination, heat, lack of lubrication, and misalignment
can all contribute to deterioration of the main bearings. Unclean
conditions such as failure to routinely change the compressor's oil
or replace the air filter, can allow dirt or
other contaminants to make their way into the oil and
eventually into the bearings. This foreign material can become
embedded in the soft bearing material and even further score or
damage the crankshaft.
Heat is also a primary factor that causes
the bearings to wear prematurely and will lead to
failure if the bearings get too hot. Being primarily cooled
by the flow of oil through and around the
bearing, anything that disrupts this oil flow raises
bearing temperature and increases the risk of damage to the
bearing. Lack of lubrication can cause fusing due to the
excessive friction from metal to metal contact that happens in the
absence of oil. Another contributing factor to bearing wear is
misalignment, which is indicated by an uneven or diagonal wear
pattern on the rod bearings. This usually indicates
that the connecting rod has been bent and
should be replaced.