What You're Doing When You Replace a Valve Cover Gasket

A valve cover gasket is a rubber or cork seal that sits between your engine's valve cover and the cylinder head. When it wears out, oil leaks onto the engine block and you'll see dark stains or smell burning oil when the engine is hot. Replacing it means removing the valve cover, scraping off the old gasket, cleaning the surfaces, and installing a new gasket with a fresh valve cover if needed.

This is a job most home mechanics can do in one to three hours, depending on your vehicle's layout. You don't need a lift or special tools beyond what's in a basic socket set, a scraper, and gasket sealant. The hardest part is usually access—some engines pack the valve cover under hoses, wiring, and brackets that have to come off first.

Key Takeaways

  • You'll need the correct gasket for your specific year, make, and model—buy it before you start, because the wrong one won't seal.
  • Let the engine cool completely before you touch anything, because the valve cover and surrounding metal get hot enough to burn skin.
  • The old gasket material sticks hard to the cover and head; scrape it completely clean or the new gasket won't seal properly.
  • Most valve covers bolt down with 8 to 12 bolts that come off in a crisscross pattern, not all at once, to avoid warping the cover.
  • Gasket sealant (RTV silicone) goes on the gasket or the sealing surface depending on your gasket type—check the instructions that come with it.

Gather Your Tools and Parts Before You Start

Get the correct gasket first. Write down your vehicle's year, make, model, and engine size, then go to an auto parts store or order online. A universal gasket almost never fits right. You'll also need a new valve cover if the old one is cracked, warped, or the bolt holes are stripped.

Collect these tools: a socket set (usually 8 mm to 13 mm), a ratchet, a screwdriver set, a gasket scraper or putty knife, a wire brush or brass brush, clean rags, and gasket sealant (RTV silicone). Some engines need a breather hose removed, so have a hose clamp handy. Work on a level surface with the engine cold—at least two hours after the last run.

Remove Everything Between You and the Valve Cover

Take a photo of the engine bay with your phone before you disconnect anything. This saves time when you reassemble. Disconnect the negative battery terminal first—this prevents accidental shorts if a wrench touches metal.

Remove hoses, wires, and brackets that sit on top of or around the valve cover. The breather hose usually clips or bolts on; the ignition coil pack or spark plug wires pull straight off (twist gently if they're stuck). Write down where each wire goes or take another photo. Some covers have a PCV hose that connects to the intake manifold—note which end goes where before you pull it free.

Once the cover is clear, you can see all the bolts. Count them and note their positions—they're usually the same size, but some engines have one or two different lengths that go in specific spots.

Unbolt the Valve Cover in the Right Order

Loosen all the bolts a quarter turn first, then go around in a crisscross pattern (like tightening a car wheel) and remove them completely. This spreads the pressure evenly and prevents the cover from warping. If you remove bolts in a line from one end to the other, you can bend the cover and create a leak that won't seal.

Lift the cover straight up. It may stick because the old gasket has dried and hardened—tap the edge gently with a rubber mallet if it won't budge. Don't pry with a screwdriver, because you can crack the cover or damage the sealing surface on the cylinder head.

Set the cover on a clean surface. If you're reusing it, keep it where dirt won't fall into it. If it's cracked or warped, set it aside for recycling.

Scrape and Clean the Sealing Surfaces

This step determines whether your new gasket leaks. The old gasket material is stuck to both the valve cover and the cylinder head, and you have to remove every bit of it.

Use a gasket scraper or old putty knife to scrape the valve cover first. Hold the scraper at a shallow angle and push away from you, working in one direction. Flip the cover and scrape the other side. Switch to a wire brush and scrub away any remaining flakes or residue. Wipe the cover clean with a rag.

Now scrape the cylinder head where the gasket sat. This surface is usually aluminum and scratches easily, so use a plastic scraper if you have one, or go slow with the metal scraper. Once the old gasket is off, use the wire brush to clean away any loose material. Wipe the head clean with a rag. The surface should look bare metal or aluminum with no black or brown residue.

If gasket material is stuck in tight corners, soak it with gasket remover spray (available at any auto parts store) and let it sit for 10 to 15 minutes, then scrape again. Don't rush this—a dirty surface is the most common reason a new gasket leaks.

Install the New Gasket and Valve Cover

Check the instructions that came with your gasket. Some gaskets are pre-glued and need no sealant; others are dry and need a thin bead of RTV silicone on the gasket itself or on the sealing surface. If your gasket is pre-glued, skip the sealant. If it's dry, explore a thin, continuous bead around the gasket groove on the cover, or on the head if the instructions say so. Don't use too much—excess sealant can squeeze out and block oil passages.

Set the gasket in place on the cylinder head, making sure it sits flat in the groove. Lower the valve cover straight down and align the bolt holes. Insert all the bolts by hand first—this prevents cross-threading.

Tighten the bolts in a crisscross pattern, the same way you loosened them. Tighten a quarter turn, then go around again, then another quarter turn, until all bolts are snug. Don't crank them down hard—valve cover bolts are usually 7 to 10 foot-pounds of torque, which is hand-tight plus a little more. Over-tightening can crack the cover or strip the threads.

Reconnect Everything and Test for Leaks

Reconnect the breather hose, PCV hose, ignition coils, and spark plug wires in the reverse order you removed them. Use your photos as a guide. Make sure hose clamps are tight and wires are seated all the way on the coils.

Reconnect the negative battery terminal. Start the engine and let it idle for two minutes. Look for oil leaks around the valve cover edges. If you see drips, turn off the engine and let it cool, then tighten the bolts another quarter turn in a crisscross pattern. Restart and check again.

Let the engine run for 10 minutes, then turn it off and let it cool for an hour. Check underneath the car for fresh oil spots. If the gasket is dry after an hour of cooling, you're done. If oil is still dripping, the gasket may be seated wrong or the surfaces weren't clean enough—you'll need to remove the cover and start over.

Common Mistakes That Cause Leaks

The most common error is not cleaning the old gasket material completely. Even a thin film of old rubber or cork will prevent the new gasket from sealing. If you rush the scraping step, you'll have a leak within days.

The second mistake is over-tightening the bolts. Valve cover bolts are small and straightforward to strip, and over-tightening can warp the cover. Hand-tight plus a quarter turn is usually right. If a bolt won't tighten after a few turns, stop—the hole may be stripped and you'll need a new cover.

The third mistake is using the wrong gasket. A gasket that's slightly too small or too large won't seal properly. Always confirm the part number matches your vehicle before you buy.

Frequently Asked Questions

How long does a valve cover gasket last?

Most gaskets last 50,000 to 100,000 miles, depending on engine temperature and oil quality. Some last longer; some fail early if the cover warps or bolts loosen. If you see oil leaking from the valve cover area, the gasket is probably done.

Can I drive with a leaking valve cover gasket?

Yes, but not for long. A slow leak just makes a mess under the car. A fast leak can drain your oil quickly, and a dry engine will seize in minutes. If you notice the leak, plan to replace the gasket within a week or two. Check your oil level every time you drive.

Do I need to replace the valve cover itself?

Only if it's cracked, warped, or the bolt holes are stripped. If the cover looks solid and the bolts tighten firmly, reuse it. A new cover costs more than a gasket and isn't always necessary.

What's the difference between RTV silicone and gasket sealant?

RTV (room-temperature vulcanizing) silicone is a type of gasket sealant that cures at room temperature without heat. Most valve cover gaskets work with RTV. Some gaskets are pre-glued and don't need sealant at all. Check your gasket instructions.

Why is my new gasket leaking after I installed it?

The most likely reason is that the old gasket material wasn't completely removed from the sealing surfaces. Oil can seep through tiny gaps between the new gasket and the head or cover. Remove the cover, scrape both surfaces again, and reinstall. The second reason is over-tightening, which can warp the cover—loosen the bolts and retighten in a crisscross pattern to hand-tight plus a quarter turn.