Severity Level: Medium/Low – Have this checked out this week
Why is my car leaking oil?
A motor oil leak can be messy. But it can also be a sign of significant engine trouble – now or down the road.
Motor oil, also referred to as “engine oil”, ensures that all of the moving parts inside your engine are lubricated. It does so by creating a wafer thin layer, a liquid barrier between components so that they do not make metal to metal contact with one another. Many internal engine parts are moving at thousands of revolutions per minute. So, adequate lubrication is essential. The oil also serves to keep your engine from overheating by reducing friction.
The motor oil is housed at the bottom of your engine in a receptacle called an oil pan. When your engine is running, a pump (the oil pump) forces the fluid throughout the inside of the engine block. There, oil coats the pistons, engine valves, crankshaft, camshaft(s), and more. To keep the oil from becoming contaminated from tiny bits of metal debris or dirt, it is cycled through an oil filter. Some heavy duty and performance vehicles rely on an oil cooler to help dissipate engine heat absorbed by the oil.
What causes a motor oil leak?
Unfortunately, it is not always easy to keep the oil contained inside your engine. Oil is prone to seep out of gaps between different parts of the engine. For instance, the connection between the cylinder head and the engine block is sealed by a gasket. If the gasket fails, oil can leak out of the seam. The part of the engine where the crankshaft is attached to the crankshaft pulley is another place where oil can leak if the seal goes bad. Anywhere there is a seam or opening in the engine is a potential for an oil leak.
There are two questions when it comes to the cause of a motor oil leak: why is the oil leaking, and where is it leaking from?
Oil can leak for a number of reasons. The most likely is when a seal or gasket fails. But oil can leak if a component is left loose as well. An oil filter or drain plug that was improperly tightened during an oil change can lead to a leak. So can a poorly torqued oil pan, valve cover, or cylinder head.
Poor vehicle maintenance can also cause oil to leak. Oil tends to break down over time. It gets thin and loses some of its lubricating ability. But it also gets contaminated, and when it does, it becomes acidic. Eventually, the oil can contaminate and degrade engine seals if you do not make sure to get regular oil changes for your engine.
Finally, engine overheating can also cause problems that lead to a leak. If a cylinder head or other component warps due to overheating, oil can escape.
Where do oil leaks come from?
A motor oil leak can come from several places on an engine, including:
- The oil pan. This is the receptacle located underneath your engine where the oil is stored.
- The valve cover(s). These are located on top of the engine and keep dirt and debris from getting inside where the intake and exhaust valves are working.
- The drain plug. This plug is a bolt that can be removed to drain oil from the oil pan during an oil change service.
- The oil filter. The oil filter can be mounted near the top, bottom, or side of an engine, depending on the vehicle manufacturer. Oil can also leak from the filter housing.
- The front or rear main seal. These parts seal the ends of the crankshaft where they mount to the engine block.
- The camshaft seal. This part helps to seal the ends of the camshaft(s) near the top of your engine.
- The timing cover. Engines that feature a timing chain can develop a leak around the cover at the front face of the engine.
How do I know if my engine is leaking oil?
Most of the time, it is fairly obvious when an engine is leaking oil. You can often see a telltale puddle of fluid underneath the front of your vehicle. Or a black oil spot on the driveway or in the garage. You might notice a leak inside the engine compartment as well. Sometimes you might smell a burning odor, especially if the oil is dripping onto a hot exhaust surface. And sometimes engine accessories and the serpentine drive belt can become coated with leaking oil.
But not all motor oil leaks are easy to identify. There are times when a leak is small and subtle. It may take quite a while to notice. And not every motor oil leak is external. Sometimes an oil leak is internal. Say a head gasket fails. Some of the oil can leak into parts of the engine where it does not belong. If it gets into the combustion chambers (cylinders), you will likely notice some black smoke coming from the exhaust. And if it mixes with the engine coolant, you will see murky antifreeze upon inspection. A timing belt might become oil soaked due to an internal leak as well.
One way to tell if your engine is losing oil is by checking the oil level with the dipstick. Simply remove the dipstick from its tube, clean off any residual oil at the end, replace the dipstick, and remove it again. Then check to make sure the oil level on the stick reads in the recommended zone. Unfortunately, while this maintenance procedure can let you know if the oil level is low, it does not directly tell you there is a leak. Most older engines – and many new ones – burn a good deal of oil naturally. It is common for the oil level to drop between oil changes.
So, a low reading on the dipstick might be evidence of an oil leak, but it is not definitive. You will need an inspection for that.
Is it okay to drive if my engine is leaking oil?
Whether or not it is a good idea to drive with an oil leak from your engine depends on the severity and location of the leak. It is possible to drive for a short while with a minor leak, say from a valve cover gasket. And if a bit of oil leaks into the combustion chamber, you might see a little black smoke, but you can drive for a while. But it is not recommended to drive for very long with an internal leak between the oil and coolant. Nor should you drive when a lot of oil is coating your spark plugs.
Certainly, a large leak means that your engine will be insufficiently lubricated should the oil level drop considerably. If the oil coats other components, like the drive belt, alternator, or timing belt, serious or even dangerous problems can arise. At the very least, your driveway or garage will receive a rather large stain.
If you notice a small oil leak, it should be fine to top off the oil occasionally and wait to have your engine serviced. But if the leak grows or is large, have it inspected and serviced sooner than later.
How do I fix a motor oil leak?
The repair for an oil leak depends entirely on the location of the leak. If the leak originates with the oil pan seal, then the seal must be replaced by draining the oil and removing the oil pan to access the old seal and replace it with a new one. Some of the repair services related to an oil leak include:
- Valve cover gasket replacement
- Cylinder head gasket replacement
- Oil pan gasket replacement
- Front main seal replacement
- Rear main seal replacement
- Oil filter replacement
- Oil filter housing replacement
Oil leak repairs should be left to a qualified technician at a trusted repair shop. If you suspect that your engine is leaking oil, have it inspected soon.
Oil Leak FAQs
What causes oil leaks?
Oil leaks can be caused by deteriorated engine seals and gaskets, loose components, damage from overheating, and degraded oil that has not been changed frequently enough.
Where do oil leaks come from?
An oil leak can originate from valve covers, crankshaft seals, timing covers, head gaskets, and more. Essentially, any junction or joint in an engine has the potential to leak.
How do I know if my engine is leaking oil?
You might see a pool of oil on the ground or in your engine compartment if your engine is leaking. But not all leaks are external. Some oil leaks occur inside of an engine.
How long can I drive with an oil leak?
In some cases, you can get away with driving for some time with a minor oil leak. However, if the leak progresses or is a large leak to begin with, have it serviced soon.
How do I prevent oil leaks from my engine?
You can prevent many motor oil leaks by making sure to provide regular preventative maintenance on your engine. Especially frequent oil changes with quality motor oil.
