What a valve gasket cover does and why it fails

A valve gasket cover (also called a valve cover gasket) is a rubber or cork seal that sits between your engine's valve cover and the cylinder head. Its job is to stop oil from leaking out where those two metal parts meet. When the gasket fails — usually after 50,000 to 100,000 miles, though this varies by engine type and driving conditions — oil seeps onto the outside of the engine, and you may smell burning oil or see stains under your car.

The gasket fails because heat and oil break down rubber over time. You cannot repair a failed gasket; you have to replace it. The job itself is straightforward on most cars: remove bolts, lift off the cover, scrape out the old gasket, install a new one, and bolt the cover back down. On some engines the valve cover sits in an straightforward-to-reach spot; on others it is buried under intake manifolds or other components that have to come off first.

Key Takeaways

  • A valve gasket cover replacement involves removing the valve cover, scraping away the old gasket, and installing a new one with fresh sealant.
  • The job takes 30 minutes to two hours depending on engine layout and how accessible the valve cover is on your specific vehicle.
  • You will need the correct gasket for your make, model, and year — buying the wrong one means it will not seal properly.
  • Most of the cost is labor if you take it to a shop; the gasket itself usually costs between $10 and $50.

Gather the right gasket and tools before you start

Before you touch anything under the hood, you need the correct replacement gasket. Go to an auto parts store with your vehicle's year, make, model, and engine size, or look it up on the store's website. A gasket for a 2015 Honda Civic will not fit a 2015 Toyota Corolla, and using the wrong one means the cover will not seal and oil will still leak.

You will also need a socket set (usually 8mm to 13mm sockets), a ratchet, a gasket scraper or plastic putty knife, new gasket sealant (often called RTV silicone or anaerobic sealant — check what your gasket requires), a clean rag, and possibly a torque wrench if your engine manual specifies bolt torque values. Some valve covers bolt down with a specific tightness; over-tightening can crack the cover, and under-tightening leaves gaps where oil leaks through.

Remove the valve cover and old gasket

Disconnect the negative terminal of your battery and let the engine cool completely. A hot engine can burn you, and disconnecting the battery prevents accidental shorts if you bump something while working.

Locate the valve cover — it is the large metal or plastic lid on top of the engine. Unplug any sensors or wiring harnesses clipped to it, noting where they go so you can reconnect them later. Remove all bolts holding the cover down; lay them out in order so you remember which bolt goes where (some engines use different bolt lengths). Gently pry the cover up with a plastic tool or screwdriver; do not force it or you may crack the cover itself.

Once the cover is off, you will see the old gasket stuck to either the cover or the cylinder head (or split between both). Use a gasket scraper, plastic putty knife, or old credit card to scrape away all the old material. Do not use a metal scraper on aluminum covers — you will gouge them. Wipe the surface clean with a rag and solvent (brake cleaner works well) until no gasket material or oil residue remains. A clean surface is essential; if you install a new gasket over old debris, it will not seal.

Install the new gasket and sealant

Check your gasket package to see if it comes pre-glued or if you need to explore sealant. Many modern gaskets are pre-glued and just press into place; others require you to explore a thin bead of RTV silicone or anaerobic sealant to the cover or head first. Follow the instructions that came with your gasket.

If you are explore sealant, run a thin, even bead around the entire sealing surface — not too much, or it will squeeze out and make a mess. Press the gasket firmly into place, making sure it sits evenly in the groove. If the gasket has a lip or notch, align it correctly so it does not twist as you bolt the cover back down.

Bolt the cover down and reconnect everything

Reinstall the valve cover bolts in reverse order of how you removed them. If your engine manual specifies a torque value (often 7 to 10 foot-pounds for most engines), use a torque wrench and tighten each bolt to that value. If no value is given, tighten the bolts snugly — firm enough that the cover does not move, but not so hard that you crack the cover or strip the bolt holes.

Reconnect any sensors, wiring harnesses, or hoses you unplugged. Reconnect the negative battery terminal. Start the engine and let it idle for a few minutes, watching for any oil leaks around the cover. If you see drips, turn off the engine, let it cool, and check that all bolts are tight and the gasket is seated evenly.

When to take it to a shop instead

On some vehicles — particularly turbocharged engines, engines with complex intake manifold layouts, or cars where the valve cover is underneath other components — removing the cover requires taking off other parts first. If your engine manual shows that you need to remove the intake manifold, alternator, or air filter housing to reach the valve cover, the job becomes a half-day or full-day task.

A shop will charge you labor time (usually $75 to $150 per hour) plus the cost of the gasket and sealant. On a straightforward engine, expect $150 to $300 total. On a complex engine, expect $300 to $600. If you are not comfortable working under the hood or your engine layout is complicated, a shop is the faster and safer choice.

Frequently Asked Questions

Can I drive with a leaking valve cover gasket?

Yes, but not for long. A slow leak means you will lose oil gradually, and if the oil level drops too far, you risk engine damage. Check your oil level weekly and top it up as needed. A fast leak that drips onto hot engine parts can cause a burning smell or even a small fire, so have it replaced soon.

Do I need to replace the valve cover itself?

Only if it is cracked or the bolt holes are stripped. Most of the time you are just replacing the gasket. If you crack the cover while removing it, a new cover usually costs $30 to $100 plus labor to install it.

How long does the new gasket last?

A properly installed gasket typically lasts 50,000 to 100,000 miles, the same as the original. Some last longer if you keep up with oil changes and do not let the engine run too hot. If your gasket fails again within a few thousand miles, the cover may be warped or the bolts may not be tight enough.

What if I over-tighten the bolts?

Over-tightening can crack a plastic valve cover or strip the bolt holes in the cylinder head. If the holes are stripped, you may need to use a larger bolt with a helicoil insert, or have the head re-tapped. Tighten snugly but not hard — if you are using a torque wrench, follow the manual value exactly.