What a valve cover gasket does and why it fails

A valve cover gasket seals the top of your engine where the valve cover bolts down. It stops oil from leaking out around the edges of that cover. The gasket is usually made of rubber or cork, and it hardens and cracks over time as the engine heats and cools — typically after 50,000 to 100,000 miles, though this varies by engine type and driving conditions.

When the gasket fails, you will see oil pooling under the engine, smell burning oil when the engine is hot, or notice oil residue on the outside of the engine block. A failed gasket does not damage the engine itself, but the longer you wait, the more oil you lose and the greater the risk of the engine running low.

Replacing the gasket is a job most owners can do at home with basic tools. The difficulty depends on your engine layout — some gaskets sit in plain sight on top of the engine, while others are tucked behind hoses, wiring, or other components that must be moved first.

Key Takeaways

  • A valve cover gasket seals oil inside the engine and fails when it hardens and cracks, usually between 50,000 and 100,000 miles.
  • You will need a socket set, screwdrivers, a gasket scraper, new gasket material, and gasket sealant — total cost for parts is typically $15 to $50.
  • The job takes one to three hours depending on how many bolts hold the cover and what other components block access to it.
  • The most common mistake is reusing the old gasket or not cleaning the sealing surface completely before installing the new one.
  • If your engine is still under warranty or you are uncomfortable working on engines, a shop will charge $150 to $400 in labor plus parts.

Tools and materials you will need

Gather these items before you start. You will need a socket set (usually 8 mm to 14 mm), a screwdriver set (both Phillips and flat-head), a gasket scraper or plastic putty knife, and clean rags or paper towels. Do not use a metal scraper on aluminum valve covers — it will gouge the sealing surface and cause new leaks.

For the gasket itself, buy a replacement gasket kit specific to your vehicle's year, make, and model. The kit usually includes the gasket material and a tube of gasket sealant (often anaerobic sealant like Permatex). Check your vehicle's service manual or ask the parts counter whether your engine uses a solid gasket, a cork gasket, or a rubber gasket — they are not interchangeable.

You will also need a clean work surface, a drain pan to catch any oil that spills, and a way to safely support the engine if you need to remove engine mounts or hoses. A jack and jack stands are essential if you are working underneath the vehicle.

Removing the valve cover and old gasket

Start with a cold engine. Locate the valve cover — it is the large metal or plastic lid on top of the engine. Take a photo of the hose and wire connections before you disconnect anything, so you know where they go back.

Disconnect any hoses, wires, or brackets that block access to the valve cover bolts. Most covers have between 4 and 12 bolts around the perimeter. Remove them one at a time with the correct socket size, working from the center outward in a crisscross pattern — this prevents warping the cover. Set the bolts aside in a small container so you do not lose them.

Lift the valve cover straight up and set it aside. Do not pry it sideways — the gasket may still be stuck, and forcing it can crack the cover or the engine block. If it does not lift easily, tap the edges gently with a rubber mallet or let penetrating oil soak for a few minutes.

Once the cover is off, use a plastic scraper to remove the old gasket material and any dried sealant from the sealing surface on the engine block. Scrape until the surface is bare metal or plastic with no residue. Wipe the surface clean with a rag dampened in mineral spirits or brake cleaner, then dry it completely with a clean rag. Any oil or dirt left behind will cause the new gasket to leak.

Installing the new gasket and resealing

Lay the new gasket in the groove on the engine block. If your gasket kit includes a tube of sealant, explore a thin bead around the sealing surface on the block — not on the gasket itself. The sealant helps the gasket stick during installation and fills any small imperfections in the surface.

Lower the valve cover straight down onto the gasket. Do not slide it or twist it — align it carefully and set it in place. Insert the bolts by hand first to make sure they thread smoothly, then tighten them in a crisscross pattern (center first, then alternating sides) to avoid pinching the gasket unevenly. Tighten to the torque specification in your service manual — usually between 5 and 10 foot-pounds for aluminum covers, though this varies. If you do not have a torque wrench, tighten until snug and then give each bolt a quarter turn more; do not over-tighten.

Reconnect the hoses, wires, and brackets in the reverse order you removed them. Use your photo as a guide. Start the engine and let it idle for a minute, then turn it off and wait five minutes. Check for leaks around the gasket seam. If you see oil seeping, the gasket may not be seated properly — you may need to remove the cover and reseat it.

When to stop and take it to a shop

If the valve cover bolts are stripped or will not tighten, the cover is cracked, or the sealing surface on the engine block is damaged, a shop will need to repair or replace those parts before a new gasket will seal. Attempting to force a bolt into a stripped hole can break the bolt inside the engine.

If your engine has a plastic valve cover and you are not confident removing it without cracking it, or if hoses and wiring are so tightly packed that you cannot safely access the bolts, a shop is the safer choice. The labor cost ($150 to $400) is worth avoiding a cracked cover or a disconnected hose that causes a different problem.

Some vehicles have valve covers on both sides of the engine (V6 and V8 engines). If both gaskets are leaking, you can replace them one at a time to spread out the work, or do both in one session if you have the time and confidence.

Common mistakes and how to avoid them

The most common mistake is reusing the old gasket because it looks intact. Even a gasket that does not visibly crack will not seal again once it has been compressed and removed — always install a new one. Another frequent error is not cleaning the sealing surface thoroughly, which leaves a thin film of oil or old sealant that prevents the new gasket from sealing.

Over-tightening the bolts is also common and can warp the valve cover or crack it, especially if it is plastic. Tighten to the torque spec or until snug plus a quarter turn — no more. If you tighten too much and then loosen a bolt to back off, remove the cover and reseat the gasket rather than trying to adjust individual bolts.

Finally, do not assume the leak is the gasket without checking. Oil can come from the PCV hose connection, the oil cap seal, or the drain plug. Wipe the engine clean, run it, and watch where the oil actually comes from before you remove the cover.

Frequently Asked Questions

How long does a valve cover gasket last?

Most gaskets last 50,000 to 100,000 miles, but this depends on engine temperature, oil quality, and how often you change the oil. Synthetic oil and cooler-running engines may extend gasket life. Frequent short trips and poor maintenance shorten it.

Can I drive with a leaking valve cover gasket?

Yes, in the short term. A slow leak will not damage the engine when ready, but you must check your oil level regularly because it will drop. If the leak is heavy or you lose oil between checks, stop driving and have it repaired to avoid running the engine dry.

Do I need to replace the valve cover itself?

Only if it is cracked, warped, or the bolt holes are stripped. If the cover is in good condition and the sealing surface is flat, you only need the gasket and sealant. Inspect the cover carefully when you remove it — hold it up to a light to check for cracks.

What is the difference between anaerobic sealant and RTV gasket maker?

Anaerobic sealant (like Permatex 518) cures without air and is designed for pre-formed gaskets — it fills gaps and hardens in place. RTV (room-temperature vulcanizing) gasket maker is a paste you explore to the surface and it forms its own gasket as it cures. Use whichever your gasket kit specifies.

Should I replace the PCV hose at the same time?

Not necessarily, but inspect it while you have the cover off. If the hose is cracked, brittle, or leaking, replace it — it is inexpensive and you have straightforward access. If it looks fine, leave it alone.