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What’s That Smell? Identify and Fix a Valve Cover Gasket Oil Leak

Posted by Michael Manning on

Don’t Let Your Engine Run Low On Oil – It Can Cause Serious Engine Damage

The smell of burning oil, an engine that is running rough or has a rough idle, or your engine oil is low when checking with the oil dipstick, are all signs that you may have an oil leak. But where is the oil leaking from? Usually, you will find spots of oil under the car on your street or driveway when parked. The location of that oil spot is often the first indication of what is leaking under the hood. If the leak is near the front or center of the engine, it is likely a valve cover leak. Let’s diagnose and find out.

How Do I Know If My Valve Cover Gasket Is Leaking?

The valve cover gasket prevents oil from leaking out of the valve cover. The valve cover protects and keeps the valve train components lubed. This is all located at the top of the engine’s cylinder head. If you notice a sticky ring of debris around the seal of the valve cover gasket, it’s a safe bet that it’s leaking but let’s read further and learn more about this integral component of your car’s engine.

Why is my valve cover gasket leaking?

Valve cover gaskets are typically made of a type of plastic, rubber, or cork to maintain a tight seal. The seals are often reinforced with a heat-tolerant caulk-like sealant called “gasket sealant”. Over years of heat, vibration, oil build-up, and debris the gasket material starts to get brittle, crack, and deteriorate. When a valve cover gasket does this, oil pressure from the image will cause oil to seep between the gasket and the cover, causing the oily residue we mentioned earlier.

What are other signs of an oil leak?

Your Engine Oil is Low

Being low on oil doesn’t mean it’s coming from your valve cover gasket but it’s one possibility. Checking your engine oil on a regular basis is a good way to get ahead of this issue and can give you a clue that there’s a leak somewhere.

Your Engine Is Running Rough or Misfiring

The valve cover usually curves around your spark plugs so a leaking valve cover gasket could cause oil to drip down around the plugs which can affect your spark and cause your engine to run and idle roughly or even misfire.

The Smell of Burning Oil

Your valve cover is generally located on the very top of your engine which means it’s above the hottest things under your hood, including your exhaust manifold. Any leak from the valve cover can cause smoking and the oil burning smell by dripping on the hot components below. If the leak is more advanced or heavier than a simple drip, the oil may catch fire instead of just burning off, causing a much more dangerous situation.

Pressure Build Up in the Valve Cover

Your PCV valve is there to relieve pressure from the valve cover. If that valve becomes clogged then the pressure build-up can cause the valve cover gasket to fail because it is the weakest point of the sealed component. When that gasket fails oil will begin to leak from the valve cover.

It’s time to diagnose and fix a bad valve cover gasket

  1. Locate the seam of the valve cover

Some vehicles have a plastic shield covering the whole top of the engine. If your car or truck has one of these, remove it move first, and then look for the valve cover and where it meets the top of the engine. Follow any traces of oil you find back to the source.

  1. Remove the valve cover

In this blog, we are going to say the issue is a bad valve cover gasket. You have to remove the valve cover from the cylinder head. There are several bolts around the outside of the valve cover so make sure you put them in a safe place so you don’t lose them or drop them inside of the engine. In later model vehicles, the ignition coils are often on top of the spark plugs. If that’s the case, make sure you remove these before taking off the valve cover. You do not need to remove the spark plugs. 

Mechanic’s note: Four-cylinder engines are typically easier than 6 and 8 cylinders, depending on the year, make, and model, of course, but in some cases, you may need to remove an air intake system. This sounds and may look daunting but it is usually a pretty simple task as well. Overall, replacing a valve cover gasket isn’t a very difficult job when compared to some other mechanical tasks.

  1. Check your PCV valve

Look at your PCV valve and see if it looks clogged or incredibly dirty. If it is, replace it because it could be the cause of your issues, and simply replacing the valve cover gasket alone may not fix the deeper issue. These vary quite a bit between different years, makes, and models, so check your owner’s guide or do a Google search for the proper steps.

  1. Replacing the valve cover

Make sure the surface where the gasket goes is clean, on both the cylinder head and the gasket cover. Squeeze a small bead of the sealant onto the surface of the cylinder head and the valve gasket cover. Place the gasket on the cylinder head to match the shape and bolt patterns. Replace the cover and bolt it down.

Mechanic’s Note: When seating any sealed item like a valve cover gasket, it is best to tighten every other bolt a few turns each to make sure they are all tightened evenly. If you tighten one all the down and then the next, the last bolts may not be as tight or seated as the first, which could cause the gasket to fail sooner than it should.

Reinstall the coil packs and any hoses you removed. 

  1. Clean remaining oil from the engine

You can use brake parts cleaner or engine degreaser to clean up excess oil from around the valve cover, cylinder head, oil fill cap, etc. Cleaning this up does two things; it helps stop the oil burning smell immediately and allows you to identify new oil leaks more quickly.

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