Signs of a bad PCV valve are not always evident, and can go undetected if you are not diligent about keeping up the maintenance. The first thing you may notice is decreased performance coupled with increased fuel consumption. That is because the valve may be stuck either open or closed, which would build up air pressure on either side of it causing an imbalance of your air/fuel ratio. You may also see some oil leaking out of your valve cover. This would indicate that the blow-by from your crankcase is not escaping through the PCV valve and being forced around it or out other seals, grommets, or gaskets. An oil leak spells trouble because you want every bit of oil circulating through your engine to keep the internals lubricated and moving smoothly. Testing to see if your PCV valve is malfunctioning is an easy task. All you have to do is start your engine and let it run for a few minutes, pull the valve from its location (keeping the return hose connected at the top), and see if suction is coming from the bottom. If not, it is blocked and needs to be replaced.
Inside every internal combustion engine, very small amounts of exhaust gases will sneak down past the pistons during the 4-stroke cycle and enter the crankcase. Positive crankcase ventilation (PCV) was conceptualized in the 1950's in response to theories that simply venting those blow-by gases into the atmosphere (the method previously used to get rid of them) was causing smog. By the 1960's, automakers were creating passageways that led from the lower engine block to a PCV valve which would then slowly vent it back through the intake manifold and into the combustion chamber. Sometimes a bit of oil also escapes in this system, and an air/oil separator is used to trap and recycle the oil while re-routing the air back into the intake. PCV systems were the first collaborative method to come from the auto industry in order to actively combat air pollution (http://en.wikipedia.org/wiki/Positive_crankcase_ventilation).
The hardest part of replacing a bad PCV valve is locating and gaining access to it. On some engines it could be very easy; you may find it right on top of a valve cover or next to the intake manifold. However, you may have to look near the back of the engine or under other bolt-on accessories to find it. But once you find the PCV valve, it is very easy to replace. Often times it is pressed into a grommet at the bottom and the return hose is clamped on top of it. It can be removed and replaced with simple tools. If it is located in a special housing, disconnect all hoses first and unbolt the housing from its mounting location. Now you can replace the PCV valve.
Maintaining your car's engine is the best thing you can do to get the most life out of it. Since your PCV valve is the gateway for the recirculation of excess gases and lubricants that would otherwise be wasted, it only makes sense to replace it with a quality part. We carry original equipment and brand name aftermarket manufacturers on our website. That means that your replacement PCV valve is only a few clicks away.