![]() The valve guides may be starved for lubrication.So, valve stem seals, play a critical role in controlling valve lubrication, as well as oil consumption.įinally, with worn or incorrectly installed valve seals the: However, a low level of compression, will indicate a piston ring problem. A higher level of compression, will indicate that it’s a valve seal problem. You can also perform a compression test to see if this is the case. The final indicator of a poor valve seal is, a lack of acceleration power. But, it will still be a temporary condition, until finally the smoking stops under normal cruise. The engine will continue to burn the oil longer in this case. Upon pushing the accelerator after a long coast, burned oil will exit the tailpipe in copious amounts. As a result, oil collects toward the front of the valve cover over the head. Also, with the creation of high intake manifold vacuum, coupled with the downward slant of the engine. Especially, when descending a steep downgrade where the accelerator pedal remains static. ![]() Off-Throttle Braking Or Coastingĭuring off-throttle braking, worn valve seals will show their ugly face. However, worn piston rings and valve guides will smoke during all times of engine operation and never disappear. Blue Tailpipe Smokeīad valve seals nearly always show, an intermittent problem of oil burning. Yet the smoke will eventually disappear, after long engine operation or during periods of hot weather. If the valve seals have deteriorated enough, the blue-white exhaust smoke will last longer after start-up and acceleration. In an otherwise normal engine with good compression, rings and valve guides, bad seals will cause, a loss of oil. Excessive Oil Consumptionīad valve seals will cause, excessive oil consumption. The burning smoke will disappear, during cruising or highway speed. Huge clouds of blue-white smoke exit the tailpipe, after each acceleration from a stop. The high vacuum attracts oil in the heads, to congregate around the valve stems. Huge clouds of blue-white smoke exit the tailpipe Because, the throttle valve remains closed. When the vehicle sits at idle for prolonged periods high levels of vacuum at the intake manifold result. Idling And Or Stop And Go Drivingīad valve seals will show themselves during prolonged idling at stop signs or stop lights in congested city conditions. Consequently, smoke out the exhaust, is the end result. At some point it will end up in the combustion chamber. The oil will, slowly seep past the valve seal. The top of the head, will have some oil left over from the last time you drove. One sure-fire way to tell if you have a faulty valve seal, is to perform a cold engine test. When valve seals begin to wear or fail, they produce some obvious and unique symptoms: Cold Engine Diagnosis Valve Stem Seal Failure Symptoms, Under Different Conditions Increasingly stringent emissions regulations make it imperative, that oil not enter the combustion chamber. For this reason, a precise fit is extremely important, to get accurate oil metering. This allows a small amount of oil to slip past the seal to lubricate the guide. But, actually rides on a thin film of oil, creating a hydrodynamic seal. The seal does not actually make, direct contact with the stem. Unlike an umbrella seal, a positive seal does not move. Because, a positive seal, will prevent oil from flooding the guides. Overhead camshaft engines (OHC) require positive valves seals. As a result, causing lean misfire and a rough idle. Worn valve guides and seals will allow air to leak. Also, helps to keep intake vacuum high, for better idle quality. This minimizes oil consumption and hydrocarbon emissions. A positive valve stem seal provides a tighter seal which reduces the amount of oil that enters the guides. Consequently, because of better emissions and oil control. You will see positive type valve stem seals on most late model engines. Positive seals Positive Type Valve Stem Seals ![]() Deflector seals are a simple and effective design, and are easy to install. Also, they move with the valve stem, to shield the valve guide from excess oil. Umbrella or Deflector seals, like the name implies, deflect oil away from the valve stem. Deflector seals ( also call umbrella seals ) Deflector seals ( also call umbrella seals ) Valve stem seals come in two basic types, deflector seals ( also call umbrella seals ) and positive seals. Valve Stem SealsĬonsequently, as the engine wears oil consumption or smoke would be the first sign of a problem. The design of valve stem seals include, a precisely controlled leak.
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