How to Tell if You Have a Bad Valve Cover

A valve cover is an important part of just about every internal combustion engine that is found in a car today, but most drivers don’t have much reason to be aware of it on a day-to-day basis.

At or near the top of every car engine that runs on gasoline or diesel fuel, directly above the cylinders, there is an assembly of parts known as the valvetrain. The valvetrain is made up of the valves, the valve springs, the camshafts (in an overhead cam engine), and all the other hardware needed to operate the valves.

The valvetrain is responsible for letting the fuel-air mixture into the cylinders to be burned, and then to let the burned fuel out of the cylinders, allowing it to flow through the exhaust system and out of the vehicle. The valvetrain is constantly bathed in oil that circulates through the engine, both to lubricate the moving parts and to keep them cool. To retain the oil within the valvetrain assembly (as well as the entire engine), and to keep external debris out, there is a cover that fits on top of the valvetrain. This cover, known as a valve cover, is kept sealed tight with a gasket. Valve covers may be made of metal or plastic.

Inline engines, those with one row of cylinders, have a single valve cover. V-type engines like V8s have two valve covers, one for each bank of cylinders.

What are the signs of a bad valve cover?

A bad valve cover can cause problems for your engine, primarily because it allows oil to leak out of it. If the leak from your valve cover is neglected or gets bad, it can lead to a variety of issues, including catastrophic engine damage. There are several symptoms of a bad valve cover:

• You see oil leaking from the valve cover area: You may notice evidence of one or more oil leaks coming from your valve cover, usually from the edge where the gasket seals your valve cover to the rest of the engine. This may be a small leak that drips down into other parts of the engine and eventually onto the ground under your car. It could also be a larger leak that coats the surface of your valve cover, and then attracts a layer of dirt and grime on top. Leaking oil can also damage your belts and hoses. This is most likely an indicator of a bad valve cover gasket, which your mechanic can replace.

• Your oil level remains low: You should be checking your oil level regularly. If you see that your oil level reads consistently below the full mark, even after you top it up, you could have a bad valve cover that is steadily leaking oil. If you do not check your oil often enough, you may learn of this condition when your dashboard oil warning light or Check Engine light comes on. If either of these lights come on, pull over to a safe spot as soon as possible and shut down your engine. Check and top up your oil, before any permanent damage is done to your engine from lack of lubrication and overheating. Inspect your valve cover for any leaks or oil residue. Call your mechanic right away for a fix, before it gets any worse.

• You smell burning oil: Oil leaking from a bad valve cover can drip down onto the hot parts of the engine as well as the exhaust, causing the oil to burn and smell bad. If you open your hood when you smell this, you may or may not be able to see smoke where the oil is burning. Call your mechanic and get your car to the repair shop as soon as possible. Bad things can happen when you have something burning under the hood.

• Your engine is misfiring: Many vehicles are designed so that their spark plugs are attached to the engine through openings in the valve cover, or they may be located directly below the valve cover. If you have a bad valve cover that is leaking oil, some of the oil may find its way into the openings where the spark plugs are located. The oil can keep them from operating properly, resulting in a misfire and rough engine running. In extreme cases, this could start a fire in your engine. This needs immediate attention from your mechanic.

Should you drive your car with a bad valve cover?

If you have a minor leak from your valve cover, and it's not producing any oil loss, smoke, burning smell or misfiring, it is not necessarily an urgent issue. Monitor it regularly, and also be sure to check your oil level for any sudden drops. If it gets any worse, or you notice any of the above symptoms of a bad valve cover, get your car to the repair shop without delay.

How do you fix a bad valve cover?

Most cases of a bad valve cover turn out to be caused by a leaking valve cover gasket. This can be fixed by removing the valve cover and the bad gasket, cleaning up the oil that leaked out, and reinstalling the valve cover with a fresh new gasket. Another possibility is that the valve cover itself may have cracked and then leaked. The fix for this is a new valve cover, along with a new gasket. All of the valve cover bolts should be correctly tightened and torqued for an oil-tight seal.

Can you replace a bad valve cover yourself?

If you have a reasonable amount of automotive mechanical experience, and your engine does not require any additional disassembly to gain access, you should be able to fix this yourself with basic tools.

You can purchase a kit that includes a replacement gasket at your local auto parts store, or online. You can also find and view online videos of the replacement process, so that you know what to expect. If the job seems too complicated for your skill level, leave it to your mechanic.