Valve Stem Seals

Most modern day vehicles are powered by an overhead cam engine which consists of cylinders, valves, shafts, guides and many other smaller parts. Valve stem seals are one of the smaller parts to the engine. Valve stem seals are important because they improve engine operation and the emissions quality in engines that are in heavy duty vehicles. They also are important because they can reduce fuel consumption.

The valves on an engine allow air and fuel to mix in the cylinder of the engine. At the same time, the valves also control the exhaust. Most engines these days will have poppet valves. Because of the pressure created in the cylinders when the engine is running, there is a need for rubber lip type valve stem seals to fit over the valve and seal in the oil mixture and keep it from leaking into the combustion engine crankcase. Since valve stem seals are made from rubber, they allow the valve stem guides to safely remain lubricated with oil while at the same time preventing it from leaking while at the same time metering the oil amount. This lubrication greatly improves the quality of emissions while withstanding high pressure in the exhaust and intake ports on the engine. Basically, the valve stem seals act as an oil metering device.

Internal combustion engines need a continuous film of lubrication oil between the valve stem and the valve guide. The lubrication from the oil reduces the wear and tear on the valves and reduces friction. When the friction is kept at a minimal level there will be less heat build up in the engine during operation. When there is less heat build up and the engine remains running cooler, it means there will be longer life to the engine and valves.

When the valve stem seals are bad, the oil mixture will leak. As the oil leaks it will begin to accumulate in the cylinder chamber and ultimately into the crankcase. The valve guides on the engine can become worn after time which may cause them to bind inside the valve guides. A noisy valve indicates engine wear and can result in the accelerated wear of the valve stem seal. Once the valve stem seals are worn and need to be replaced, the engine will begin using higher oil at a much higher consumption rate and the quality of the exhaust emissions will begin to deteriorate.

One sure sign that the valve stem seals are bad and need to be replaced is that you will begin to see clouds of smoke intermittently coming from the exhaust pipe. The smoke is typically a bluish color and can usually be seen when you let off on the accelerator or shift gears. The smoke is caused by excess oil that is leaking through bad valve stem seals and is being burned off in the exhaust pipe. If you do not replace the valve stem seals soon after you are aware that they are bad, a more serious problem with the engine can be the ultimate result. When worn valve stems are not replaced, the valve stems will operate at a higher temperature and the oil may then carbonize causing more problems. This increases the wear to the valve stems seals even faster. Another indication of bad valve stems is when the catalytic converter becomes fouled with oil.

If you suspect valve stem seals on your engine are bad, you should take the vehicle in to have them repaired if you do not have the ability to replace them yourself. There are several websites that sell valve steam seals that sell them for all makes of vehicles. You can also purchase them at your local auto parts store.

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