When does the valve cover gasket need to be replaced?

An engine has a valve cover that covers valve train components at the top of the engine, see this photo. A valve cover gasket seals the gap between the valve cover and the cylinder head. In most modern cars, the valve cover gasket is made of rubber. Over time and under higher temperatures, the gasket shrinks and becomes brittle, which might cause oil leaks.
Valve cover gasket Valve cover gasket.
How often should it be replaced? There are no maintenance requirements for a valve cover gasket. It only needs to be replaced if it leaks. If the valve cover gasket is old, it's also often replaced when doing a major engine repair. What are the symptoms of a bad valve cover gasket? Symptoms of a leaking valve cover gasket include oil drops under the engine, burnt oil smell under the hood and visible traces of oil coming down the engine. See a photo below.

Of course, the valve cover gasket is not the only source of possible oil leaks. There are many other engine components that can also leak oil, including cam and crank seals, front engine cover seal, PCV system, oil pressure switch and other parts. To repair an engine oil leak, the source of the leak must be identified first.

How do mechanics diagnose a leaking valve cover gasket? If the engine shows oil leaks, but the source of the leak is not clear, your mechanic may recommend cleaning the affected area and re-checking it in a few days to see where the fresh leak is coming from.
Sometimes, oil leaks from a valve cover gasket are clearly visible. For example, see this photo. You can see that oil is seeping out from under the valve cover. In some cases, a leaking valve cover gasket or O-ring may result in oil getting into the spark plug well. This issue is often discovered during the spark plug replacement.
Leaking valve cover gasket Leaking valve cover gasket
O-rings that seal spark plug wells are usually included in the valve cover gasket kit. A valve cover gasket kit (part) cost $20-$65.

How much does the valve cover gasket replacement cost? In a simple in-line 4-cylinder engine, the valve cover gasket replacement may cost $90-$175 parts and labor. In a Subaru "boxer" engine with two separate valve covers, a dealer or repair shop may charge $145-$360 for parts and labor. Replacing both valve cover gaskets in a V6 or V8 engine often involves additional labor. For example, in the 2011 V6 Ford Escape, the intake manifold needs to be removed to gain access to the rear valve cover. This adds to the cost of labor. For the mentioned V6 Ford Escape, the valve cover gasket replacement may cost $250-$330 labor plus $25-$85 part.

Should the valve cover gasket be replaced as part of a tune-up? It's not necessary to replace the valve cover gasket if it's not leaking. If it is leaking and your spark plugs are due for replacement soon, it does make sense to combine both services, as a large portion of labor overlaps.
For example, for the 2011 V6 Ford Escape we mentioned above, replacing all 6 spark plugs together with both valve cover gaskets will only add the cost of spark plugs plus very little additional labor.

How easy is it to replace valve cover gasket DIY? If it's a simple 4-cylinder engine, with proper tools and necessary skills, it's a "3" job on the difficulty scale from 1 (easy) to 10 (leave it to pros). A valve cover gasket is sold as a kit and can be ordered from a dealer, online or purchased from a local part store. You may also need a special sealant. Mechanics often use sealant to seal tight spots and corners of the valve cover gasket.

What will happen if you continue driving with a leaking valve cover gasket? It all depends on how bad the leak is. Many high-mileage cars have some "sweating" around the valve cover area. If the engine is not losing oil, there is no oil drops on the parking spot and there is no burnt oil smell, it's not a big problem. If there is a noticeable leak, your engine is losing oil that may also damage the asphalt on your driveway. If you can smell burnt oil from under the hood while driving, it means the oil vapors are in the air you breathe, which is not healthy. We have also seen cases where oil leaking from the valve cover gasket damaged the drive belt. See this photo from the post about a drive belt.