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Different seals are used in engines to keep fluids contained. The valve cover gasket is one of the most important engine seals. It helps maintain proper engine lubrication and controls the potential for messy, unsafe oil leaks. With time and heat, valve cover gaskets can fail. Knowing how the sequence works will help prevent costly repair bills.
This complete guide contains a wealth of information regarding the basic function of a valve cover gasket, along with detailed instructions on replacing a valve cover gasket.
Every modern internal combustion engine has a cylinder head. This structure contains the valves, camshafts, and lifters. Engine oil is kept in, and these moving parts are protected by a metal or plastic lid called a valve cover that is bolted over the cylinder head.
The valve cover gasket is a thin strip of rubber, cork, or silicone that sits directly between the valve cover and the cylinder head. This creates a full airtight and fluid-tight seal to prevent the oil splashing around to lubricate the valvetrain from escaping into the engine bay.
Engine oil is under pressure and exposed to high temperatures. If the gasket is not working correctly, the oil will leak out of the engine block almost instantaneously.
Once the oil leaks out, it can cover the outside of your car engine. It works as a heat insulator, making the engine hot and beyond the usual temperature. Besides, it also wears out the rubber hoses and the electrical wiring insulation over time.
Oil leaking from a bad seal is most dangerous when it drips on hot exhaust components. It is well known that exhaust manifolds get hot enough to set fire to engine oil, and that is a very serious fire hazard for a car.
Identifying the symptoms of a damaged seal is the best way to fix the issue early before it causes heavy engine damage and breakdown.
Some overhead cam engine designs (OHC) use long tubes that go through the valve cover to hold the spark plug.
Tube seals are circular rings installed on the spark plug tubes to keep the oil from filling up in the spark plug wells. They usually come with a full set of valve cover gaskets.
If the tube seals are broken, then the spark plug well will fill up with oil. Since oil conducts electricity, it will cause a short between the spark plug wire and the ignition coil and will stop the spark plug from firing. This will light up the check engine light because of a misfire code.
Replacing a valve cover gasket is an ideal project for someone who is just starting as a do-it-yourself mechanic. Four-cylinder engines have access to the upper part of the engine without difficulty.
Allow the engine time to cool before proceeding. Disconnect the negative terminal of the battery in order to eliminate risk of electrical shock. Remove any plastic covers, pipes, or brackets that might be getting in the way of removing the valve cover.
Gently unplug the wire harnesses going to the ignition coils. Remove the ignition coils or spark plug wires to fix them as necessary, so they can be reconnected later to their correct cylinder location. Unplug the PCV breather hoses connected to the cover.
Using a socket wrench, loosen all of the valve cover bolts in reverse spiral order to avoid distorting the valve cover shape. Then gently remove the valve cover from your engine.
Clean the aluminum mating surface of your cylinder head using a plastic scraper to remove any old, hardened gaskets that may have been installed before this installation. Avoid using any type of metal scraper. Be sure to clean the two surfaces using brake cleaner and a clean, lint-free rag.
Thoroughly clean the valve cover groove with a wire brush to remove all dirt and debris before pushing the new rubber gasket all the way into the groove so that it lies flat with no distortion at all. If applicable, press the new spark plug tube seals into position.
Use a tiny dot of RTV silicone sealant for high temperatures at the sharp corners or seams of the timing chain cover and cylinder head. Allow it to cure for a few minutes until it becomes tacky.
Place the valve cover back onto the engine without dropping it. When reinstalling bolts, do so with your fingers to prevent cross-threading. Consult your vehicle’s specific torque pattern and torque specifications. Follow the recommended crisscross pattern for proper bolt torque distribution.
Put the ignition coils, spark plug wires, electrical connectors, and vacuum hoses back on the engine. Reconnect the battery terminal and start the engine. Allow the engine to warm up at idle and check along the perimeter of the cover for any signs of escaping fluid.
The price for this repair can differ quite a bit depending on whether you do it yourself versus taking it to a repair shop.
If you do the work yourself, it is very inexpensive. A good replacement gasket set from a known manufacturer will cost about $10-$40 USD depending on your vehicle make and engine size.
The part price will stay low, although the hourly labor charge will be $50-$150 USD.
A leaking valve cover gasket may initially be seen as a minor inconvenience but can develop into a serious safety risk or costly engine damage if not addressed quickly. Getting this repair done early will help you maintain the health of your car and keep your engine lubricated for many more miles.