2004 Toyota Sienna - Valve Stem Seal

Replacing Valve Stem Seals

Valve stem seals, also known as valve seals, prevent oil from entering the combustion chamber through the valve stems. They are typically located at the top of the valve guides where the valve stems protrude through the cylinder head to prevent oil from leaking down the valves and into the cylinder. Over time, valve stem seals may become worn, hardened, or damaged due to age, high mileage, or exposure to extreme engine temperatures. When the seals fail, oil can leak past the valve stems into the combustion chamber, resulting in symptoms such as blue-gray smoke from the exhaust, increased oil consumption, fouled spark plugs, and reduced engine performance. Oil that has dripped onto a valve's sealing surface can also solidify when cooler air hits the hot oil, which can eventually cause your valves to not seal properly. A valve that does not fully seat or seal can result in engine misfires and rough idle, and you may notice a significant decrease in performance if your valves need to be replaced or serviced. If you notice a valve stem seal oil leak, be sure to properly diagnose the source of the issue, since problems failing piston rings can cause similar symptoms. For your next valve train repair, shop O'Reilly Auto Parts for valve stem seals, replacement engine valves, and other engine parts and seals for most vehicles.