Many cars have an overhead cam and a valve cover for service. As time passes, the seal made over the valve cover with the gasket that is attached to the head runs its course, and eventually gives in. When this happens, the gasket turns brittle, block the pressure between the cover and the engine, and ultimately leave you with oil leak.
In order to replace it, you need a few necessary tools, new gasket, and gasket adhesive. Once you have the entry to the hold down bolts and headroom to withdraw the cover, let's get our hands dirty.
Change the Gasket
Drive your car to a location where no one will distract you or ask you to remove it. You might need to spend some time in changing the gasket, so you definitely don't want to invite troubles like trespassing or any violations.
The hold down bolts have to removed, but avoid not to strip their heads. Spray some Rustbuster on it, and use a correct wrench to do the job smoothly.
Typically, the cover should slip out when you try to take it out. But on some car models, the cover might be stuck on despite all the bolts being off. If it doesn't pop up or detach on its own, that means the original seal still has the gasket holding to it.
Take a putty knife and slide it under the edge of the cover. Poke inside the cover and try to lift it off. You can also tap the edge of the knife with a hammer so that it can lift the cover easily. Aim a corner of the cover where you can slip a flat-head screwdriver in the opening; twist it a bit and free the cover.
A rubber mallet can also work as you tap slightly on the cover, and break the seal. Perhaps you have to work extra to get the cover off, but eventually, these techniques will get the job done. Avoid being too strong working around it. You might just risk bending the cover, or worse, putting a dent in it.
When the cover if out, scratch out the extra gasket sealer with the putty knife. Slowly sand the mating surface with a sandpaper. This will give you a perfect fluency. Sand off all gasket material and rubble from the surface.
The engine will be revealed by now, so cover it up with some clean rags or paper towels. You don't want to get any rubble or dust getting inside. Now take the mating surface, and use the sandpaper on it as well. Work extra hard on the mating surface as it needs to be much more smooth and without any rough, bumpy surface.
You can buy a new gasket from any auto parts store for about USD 13. Place the new gasket over the engine block, and make sure it's the right size. Match the holes properly as well. Take the gasket sealer, and smear ⅛ inch thick all around the mating surface and wipe the excess with a rag.
Leave it for a few minutes before you place the new gasket on. Once it's dry, match the holes that are on the gasket with the ones on the engine block.
Take a thin layer of gasket sealer, and smear it over the top of the new gasket. Wipe the excess with a rag. The clean rags or paper towels that were on the engine can be removed now. Now it's time to put the valve cover back on the gasket. Try to get it right the first time so that you don't make a mess of the sealer.
You'll have to check for any rubble or debris on the hold down bolts. If you do find any, spray some WD-40 and tighten the bolts depending on your specific torque. Use a crisscross method to tighten the bolts rather than one side after the other.
Clean the bottom areas of the new gasket which is on the engine block. Start the car, and check for any more oil leaks. To make sure if you didn't miss anything, take a fresh paper towel and wipe below the gasket area. If the paper towel comes clean, it means you got it right.
But, if the paper towel comes out with traces of oil, then there might 3 things that must've gone wrong.
- The bolts are not fastened according to the torque.
- The valve cover needs to set flush, and probably is warped instead.
- Some rubble or old gasket material got left behind on the mating surface or the cover.
Check all possible errors that may have been easily overlooked and fix any issues that may have occurred. The mating surface needs to be extremely clean and smooth, so use the sandpaper rigorously before you install the new gasket. Now that you're familiar working with the gasket, you can pretty much think of the job as a piece of cake.