Oil pumps don't always need to be replaced when oil pressure drops, but
when one does need to be replaced, it is important to know the ins and outs of oil pump
failure.
By far the most common reason for an oil pump to fail is from dirt or
debris in the lubrication system.
According to some data, prime culprits include wire bristles from
cleaning brushes, valve seal material, and other assorted dirt. When one
considers that oil pump clearances are in the order of .003", it is not hard to
understand why foreign material can cause oil pump failure.
Pieces of nylon cam drive gears have also ended up in
oil pumps. Don't expect the screen to filter out these objects as most have a bypass hole
or slots designed to allow oil to flow when the oil's viscosity is too high to flow
effectively through the screen. A cold start and a piece of debris can quickly lead to oil
pump lock-up.
So, whenever an oil pump is being replaced, jobbers should advise their
customers that oil systems should be flushed out thoroughly. Debris can also end up
in the pressure relief valve, possibly causing pressure to bleed off leading to a
low oil pressure situation, perhaps ending up in engine damage.
In addition, manufacturers have reported that there appears to be an
increase in post rebuild engine failures as a result of the oiling system failing to
prime itself. Reports from warranty claims have revealed completely dry oil pumps in
some cases. To avoid this, jobbers should advise all customer to immerse pumps in oil
and hand prime the oil pump before installation. Furthermore, it is not advisable to use
petroleum jelly, lithium grease lubricants as a prelube in the oil pump, or liberally in
the engine at all as they do not pump and can fill the pumping channels, curtailing is
ability to move oil.
For engines that are already assembled, but have been shipped or left
sitting in storage, it is particularly advisable to pressurize the entire oiling
system prior to start up using an electric drill as the oil pump may not be able to
pressurize the system quickly enough to prevent damage. This procedure should be performed
on any engine that has been assembled, before start up, to prevent dry start.
Courtesy Jobber News Magazine
