Why is My Car Leaking Oil?

Your car’s engine contains a collection of seals and gaskets, each of which is designed to fill the space between two mating surfaces. Most seals and gaskets are made up of a material (e.g., rubber or cork) that deteriorates over time. And when that happens, an unsightly oil leak ensues.

Oil leaks can stain your engine, tarnish your driveway, and turn your car into a jalopy. Indeed, the problem is one you’ll want to address as soon as possible.

But first, you must determine the origin of the leak.

The Most Common Sources of an Engine Oil Leak

Engine oil leaks aren’t just messy—they also pose a threat to your car’s health. Leaks can lead to a low oil level, resulting in a lack of lubrication to vital engine components. The outcome is a costly engine failure.

If your car is leaking oil, you’ll want to address the issue as soon as possible. Oil leaks can come from a variety of locations. The most common sources include:

Oil Pan Gasket

The oil pan holds a reserve of oil for the oil pump to pick up and distribute throughout the engine. A gasket provides a seal between the oil pan and the engine block. When that gasket fails, it can lead to an oily mess at the bottom of the engine.

Oil pan leaks can also happen as a result of impact damage.

Valve Cover Gasket

Your car’s valvetrain contains important bits and pieces, including the valves, rockers, etc. The valve cover (also known as a camshaft cover or rocker cover) protects the valvetrain by keeping oil in and contaminants out.

As you might guess, the valve cover gasket provides a seal between the valve cover and the engine’s cylinder head. But over time, wear and tear can lead to a leaking valve cover gasket.

Crankshaft Seal

The crankshaft is a rotating assembly inside the engine that converts linear motion into rotational force. Also, the crankshaft provides a mounting location for the crankshaft pulley at the front of the engine and the flywheel (or flexplate) at the rear of the engine.

There are two crankshaft seals: one at the front of the engine and one at the rear (also known as a rear main seal). Both are designed to prevent oil from leaking out around the crankshaft.

Camshaft Seal

Like the crankshaft, the camshaft is a rotating assembly inside the engine. But the camshaft has the unique job of opening and closing the engine’s valves.

On some engines, a single camshaft is located in the engine block. Other applications have one or two camshafts located in the engine’s cylinder head(s).

Camshaft seals are often found in overhead camshaft (OHC) engines that use a timing belt. Usually, the first sign of a leaking camshaft seal is oil sneaking out from behind the timing belt cover.

Oil Filter

As its name implies, the oil filter traps contaminants that develop in the engine oil. The oil filter should be replaced every time you change your oil. If the filter is left loose during service or has a damaged seal, an oil leak will result.

Oil Filter Adapter Housing Gasket

The oil filter attaches to (or sits inside of) the oil filter housing. There’s a gasket or seal behind the housing that can eventually wear out, causing a leak. If the engine has a cartridge-style oil filter, the filter cap or seal can also develop a leak.

Oil Drain Plug

Every time you change your oil, the drain plug must be removed and reinstalled. Because the plug sees so much action, it’s easy for it to get left loose or become damaged. Mostdrain plugs also have a seal or washer that can wear out, resulting in a leak.

Timing Cover Gasket or Sealant

Some engines have a timing chain, while others use a timing belt. Unlike timing belts, timing chains must be kept lubricated by engine oil. A timing cover protects the chain while also keeping the oil inside the engine.

A gasket (or in some cases, silicone sealant) seals the timing cover to the engine block. The gasket can eventually wear out and leak.

Oil Cooler Gasket and Lines

Some vehicles have an oil cooler that reduces the temperature of the oil. The cooler may be located inside the radiator or mounted externally.

In most cases, a pair of oil lines connect the cooler to the engine. Because the lines flex during vehicle operation, they’re often prone to leaks. If the cooler has a mounting gasket, that can develop leaks as well.

How To Fix an Oil Leak

Some vehicle owners may be tempted to use engine oil “stop leak” additives as a quick-fix solution to an oil leak. But unfortunately, additives can do more harm than good when it comes to your engine. What’s more, these products almost never provide a long term fix.

To properly fix an oil leak, you need to replace whatever seal, gasket, or component is causing the problem.

The first step is to determine where the leak is coming from. If you can’t tell immediately, clean the engine off. Then, run the vehicle and recheck for leaks.

You may also choose to use a leak detection kit that contains trace dye and an ultraviolet (UV) light.

Also, keep in mind: Cars can leak a variety of fluids, including coolant, transmission fluids, gear oil, etc. Be sure you’re actually dealing with an engine oil leak before getting started.