What a valve cover gasket does and why it fails

A valve cover gasket is a rubber or cork seal that sits between your engine's valve cover and the cylinder head. It keeps oil inside the engine where it belongs. When the gasket fails — usually after 50,000 to 100,000 miles, though this varies by vehicle — oil leaks out onto the engine block, exhaust manifold, or belts. You'll notice oil pooling under the car, a burning smell when the engine is hot, or visible oil coating the outside of the engine.

The gasket fails because heat and oil break down rubber over time. Once it leaks, the gasket must be replaced; there is no repair. The job itself is straightforward on most cars — you remove bolts, lift off the cover, scrape out the old gasket, and install a new one — but the time it takes depends entirely on what's in the way. On some vehicles you can reach the valve cover in ten minutes. On others, you need to remove the intake manifold, alternator, or air filter housing first, which can add hours.

Key Takeaways

  • A valve cover gasket seals oil inside the engine; when it fails, oil leaks onto the engine block and you'll smell burning oil or see pooling underneath the car.
  • The replacement itself takes 30 minutes to 2 hours of actual work, but removing obstacles around the valve cover can add 1 to 4 hours depending on your vehicle.
  • You need a new gasket (not a reused one), a gasket scraper or plastic tool, new valve cover bolts if yours are damaged, and possibly a new intake manifold gasket if you have to remove the manifold.
  • The job is manageable for someone with basic mechanical experience and the right tools, but if you've never worked on an engine, a shop will charge $300 to $800 depending on how many parts must be removed first.

Gather the right parts and tools before you start

Buy a valve cover gasket kit for your specific year, make, and model — not a generic one. The kit includes the gasket itself and usually a tube of gasket maker. You can find these at any auto parts store for $15 to $40. Ask the parts counter to confirm it fits your engine; valve covers vary even within the same model year.

You'll also need a gasket scraper or plastic tool to remove the old gasket without gouging the metal surfaces. A metal scraper can damage the sealing surface and cause the new gasket to leak. Pick up a plastic scraper for $3 to $5, or use an old credit card or plastic putty knife if you have one. If your valve cover bolts are corroded or damaged, buy a new set — they're usually $5 to $15 for a full set and worth replacing rather than reusing stripped bolts.

Check your vehicle's service manual to see whether you need to remove anything to reach the valve cover. If the intake manifold, alternator, or air filter housing is in the way, you may need additional gaskets for those components. Some shops recommend replacing the intake manifold gasket while you're in there, especially if it's old. Have those parts on hand before you start so you don't have to stop halfway through.

Remove obstacles and locate the valve cover

Park on a level surface and let the engine cool completely — at least two hours if the car was recently driven. Disconnect the negative battery terminal to prevent accidental shorts. Remove the engine cover if your vehicle has one (usually held by clips or bolts), then look at what's between you and the valve cover.

On many four-cylinder engines, the valve cover is when ready visible. On others, you'll need to remove the intake manifold, air intake hose, alternator, or spark plug wires first. Consult your service manual for the exact sequence — removing parts in the wrong order can damage hoses or wiring. Take photos with your phone as you go so you remember how everything connects. Label any hoses or wires with masking tape before you disconnect them.

Once the path is clear, you'll see the valve cover held down by bolts around its perimeter. Count them and note their locations — some may be different lengths. Loosen each bolt a quarter turn, then go around again and loosen them another quarter turn. This prevents warping the cover. Once they're all loose, remove them completely and set them aside in order.

Remove the old gasket and clean the sealing surfaces

Lift the valve cover straight up and set it on a clean surface. You'll see the old gasket still stuck to either the cover or the cylinder head — usually both. Use your plastic scraper to gently pry it away. Work slowly and scrape at a shallow angle to avoid gouging the metal. If the gasket is stubborn, spray it with penetrating oil and wait 10 minutes, then scrape again.

Once the gasket is off, use the scraper to remove all remaining gasket material and sealant from both surfaces. The sealing surfaces must be completely clean or the new gasket will leak. Wipe both surfaces with a lint-free cloth and a small amount of brake cleaner or mineral spirits. Let them dry completely — at least five minutes in dry conditions.

Inspect the valve cover and cylinder head for damage. If either surface is warped, cracked, or deeply gouged, it must be replaced or resurfaced before a new gasket will seal properly. Small surface scratches are normal and won't cause leaks. If you're unsure, show the parts to the auto parts store staff — they can tell you whether the damage is acceptable.

Install the new gasket and reassemble

Lay the new gasket in the groove on the valve cover, pressing it gently into place. Some gaskets come with adhesive backing; others require a thin bead of gasket maker along the sealing surface. Check your gasket kit instructions — they vary. If you're using gasket maker, explore a thin, even bead around the entire sealing surface of the cylinder head, then set the cover in place. Do not use excess gasket maker; it can squeeze out and clog oil passages.

Install the bolts by hand first, threading them in until they're snug but not tight. Then tighten them in a crisscross pattern — opposite sides alternately — to may support even pressure. Tighten each bolt a quarter turn at a time until they're all snug. Do not over-tighten; you'll crack the cover or strip the bolts. Most valve cover bolts should be tight enough that you can't turn them with your fingers, but not so tight that you need a wrench to remove them later.

Reinstall any parts you removed to reach the valve cover — intake manifold, alternator, air filter housing — in reverse order. Reconnect hoses and wires using your photos as a guide. Reconnect the negative battery terminal. Start the engine and let it run for a few minutes, then turn it off and let it cool. Check around the valve cover for leaks. If you see oil seeping out, the gasket may not be seated properly; you'll need to remove the cover and reseat it.

When to take it to a shop instead

If your vehicle requires removing the intake manifold, alternator, or other major components to reach the valve cover, the job becomes significantly more complex. A shop will charge $300 to $800 depending on how many parts must come off. If you've never worked on an engine before, this is a good reason to let a professional handle it.

Also consider a shop visit if the valve cover or cylinder head is damaged, if you're not comfortable working around engine components, or if you don't have a service manual for your specific vehicle. A shop can diagnose whether the leak is actually the valve cover gasket or something else — sometimes what looks like a valve cover leak is actually a spark plug tube seal or oil pan gasket. Paying for a diagnosis now can save you from replacing the wrong part.

Frequently Asked Questions

How long does it take to change a valve cover gasket?

The gasket replacement itself takes 30 minutes to 2 hours depending on how accessible the valve cover is. If you need to remove obstacles like the intake manifold or alternator first, add 1 to 4 hours. A shop typically quotes 1 to 3 hours of labor, which translates to $150 to $600 depending on the hourly rate and your vehicle.

Can I drive the car while it's leaking?

You can drive it short distances, but not for long. A leaking valve cover gasket means oil is escaping, and your oil level will drop over time. Check your oil level every few days and top it off as needed. If you ignore the leak for weeks, you risk running low on oil, which can damage the engine. Have the gasket replaced within a few weeks of noticing the leak.

Do I need to replace the valve cover bolts?

Only if they're corroded, stripped, or damaged. If they thread in smoothly and hold tight, reuse them. If they're rusty or the threads are stripped, buy a new set. New bolts cost $5 to $15 and are worth the peace of mind — a stripped bolt can cause the cover to vibrate loose and leak again.

What if oil is still leaking after I install the new gasket?

The most common cause is that the gasket isn't seated properly. Remove the cover, check that the sealing surfaces are completely clean, and reinstall the gasket. Make sure the bolts are tight but not over-tightened. If the leak continues, the valve cover or cylinder head may be warped and need resurfacing or replacement — have a shop inspect it.

Is the gasket maker necessary if the gasket has adhesive backing?

No. If your gasket kit includes adhesive backing, the gasket alone is sufficient. Gasket maker is used when the gasket is plain rubber or cork with no adhesive. Check your kit instructions — they'll specify which method to use. Using both can cause excess sealant to squeeze out and clog passages.