The purpose of the Oil Pump is to propel oil from the oil tank into the engine. Loss of oil pressure in your engine, increased engine operating temperature, new tapping, knocking or rattling noises, might all be signs that your oil pump is going to fail soon. The oil pump usually mounts on the side of the engine and a replacement is relatively easy to install with a screwdriver. Older style metal oil pumps may have the option to be rebuilt, but new plastic ones must be replaced if they fail.