An oil pan is a reservoir attached to the bottom of your engine to store the oil that lubricates all of the moving parts inside the engine.
Engine oil, also known as “motor oil”, is circulated throughout an engine by the oil pump when the engine is running. It also flows through a filter that removes contaminants that can be harmful and cause premature wear to engine components. Beyond lubrication of those components, the oil also serves to clean them and keep them cool. The oil begins its journey in the oil pan.
Made of steel or aluminum, a typical oil pan holds anywhere from four to six quarts of engine oil, depending on the vehicle make and model. How much oil is in your engine - the oil level - can be checked by removing a dipstick that extends into the oil pan from the engine compartment. A drain plug on the bottom of the oil pan allows old oil to be drained out when it is time for fresh oil to be installed. The oil pan is affixed to a flange on the bottom of the engine block and is sealed with a gasket.
Oil pans usually need to be replaced for one of two reasons - collision or corrosion. If an oil pan is impacted by debris on the road (or off of the road), or if the metal that makes up the oil pan is rusted sufficiently that it no longer holds oil, it will need to be replaced.
The location of an oil pan is close to the ground, making it difficult to see unless your vehicle is lifted in the air. While it is possible to detect damage to an oil pan through a quick inspection, it is more likely that you will notice a fluid leak on the ground after your vehicle has been in one place for a while. Of course, a mechanic can lift your car and take a look to verify a damaged oil pan.
To replace the oil pan on your engine, a technician must first lift and support your vehicle off of the ground for access to the bottom of the engine where the pan is located. On some vehicles, an engine crossmember (part of the lower structure of the body or frame) must be removed as well. On others, steering, exhaust, or other components may also need to be removed. And in some cases, the engine may need to be shifted out of position to get at all of the oil pan fasteners or to create space for the pan to be dislodged.
In general, however, once access is gained, steps to remove and install an oil pan include the following: