Why Is My Oil Filter Leaking?

Your engine needs oil to run, and even with frequent changes, it’s possible for debris and impurities to find their way into the lubrication system over time and wreak havoc. That’s where the oil filter comes in.

Filters protect your engine from major damage and provide an easy point of maintenance that can extend the life of your vehicle by years if they receive proper attention. An oil filter leak can compromise these gains, but if you understand what causes a leak and how to avoid it, you can take steps to keep your engine in prime condition longer.

The importance of clean motor oil

Clean motor oil is important because if the oil were left unfiltered for a period of time, it could become saturated with tiny, hard particles that can wear surfaces in your engine. This dirty oil can wear the oil pump’s machined components and damage the bearing surfaces in the engine.

How do oil filters work?

The outside of the filter is a metal can with a sealing gasket that allows it to be tightly held against the engine’s mating surface. The base plate of the can holds the gasket and is perforated with holes around the area just inside the gasket.

A central hole is threaded to mate with the oil filter assembly on the engine block. Inside the can is the filter material, most frequently made from synthetic fiber. The engine’s oil pump moves the oil directly to the filter, where it enters from the holes in the perimeter of the base plate.

The dirty oil is passed (pushed under pressure) through the filter media and back through the central hole, where it re-enters the engine.

Choosing the right oil filter

Choosing the correct oil filter for your vehicle is of the utmost importance. Most oil filters look very similar, but small differences in the threads or gasket size can determine whether or not a particular filter will work on your vehicle.

The best way to determine which oil filter you need is by consulting your owner’s manual or by referencing a parts catalog. Using the wrong filter can cause oil to leak out of the engine, or an ill-fitting filter could just fall off. Either of these situations could lead to serious engine damage.

Why Is My Oil Filter Leaking?

An oil leak can leave a few drops or a big puddle under your engine. Ignoring a leaky oil filter can quickly lead to expensive engine damage.

There are seven common reasons why an oil filter leaks. Knowing the possible causes will help you determine what steps you should take to correct the problem.

Double Gasket

The most common mistake is the dreaded oil filter “double gasket.” This happens when an oil filter is replaced. The old filter gasket sticks to the engine, and the new oil filter and gasket are installed on top of the old one.

After removing the old filter, check that its gasket is still mounted on the filter. If you accidentally double-gasket an oil filter, hopefully, it will blow out (creating a nasty mess) as soon as the engine starts and not as you’re driving down the road.

Oil Filter Gasket

Check the rubber mounting gasket to make sure it is not cut, nicked, twisted or damaged in any way, and is properly seated and snug in the filter base plate. Always install a new filter if the gasket is bad.

Be sure to clean the area where the gasket contacts the engine of dirt and grime and completely remove any old gasket material that may stick to the mounting surface. Use a degreaser to clean the gasket-contact surface and use your finger to spread a thin coat of new oil on the gasket before installing a new filter.

Over- or Under-tightening

Besides making it difficult to remove when replacing the oil filter, over-tightening can crush the filter gasket, causing it to leak. When not properly tightened, any vehicle part designed to seal against a leak will loosen from normal engine or driving vibrations and cause leaks.

Oil filters should be “hand tight” and then given a one-quarter turn to securely fasten without being too tight. Never use an oil filter wrench to tighten an oil filter — only to remove it.

Oil Filter Mounting Adapter (Filter Housing)

To mount an oil filter, some manufacturers use a filter adapter or housing that bolts to the engine, rather than attaching directly to the engine. Over-tightening the filter can damage not only the oil filter gasket but the gasket between the adapter and engine.

Check that the nipple onto which the filter threads is tight inside the adapter. Nipples can be threaded on both sides and can loosen when unscrewing the old oil filter. The filter gasket may not fully seat if the threads are loose and leak.

Damaged Threads

An oil filter’s baseplate threads are softer than the threads on the mounting nipple and can be cross-threaded if the oil filter is screwed on crooked when it’s installed. You’ll need to install a new filter if the threads are damaged.

If you screw on the new filter without any problems, and there are no apparent oil leaks, it’s still a good idea to have your mechanic check out the filter mounting nipple threads for damage.

Wrong Filter

Check your owner’s manual for the correct filter number for your specific engine. A filter may feel as though it is tight when installed, but the threads may not be exactly the same as the mounting nipple. This will cause the filter to loosen up and leak over time.

Also, the wrong filter may have the incorrect by-pass valve. The by-pass value opens to protect the engine from oil starvation if the filter becomes clogged. If you’re not sure you are installing the correct filter, leave it to your mechanic.

Damaged Oil Filter Housing

A rock, stone or road debris can puncture the oil filter outer housing shell. If oil is spurting from the filter, turn your engine off and immediately call for a tow to your repair shop.