PCV Valve Function, Bad Symptoms and Cost to Replace


As you may know, the internal combustion process generates a lot of toxic exhaust gases. Fortunately, vehicles are built with an exhaust system. Whenever these exhaust gases are produced, there is an exhaust valve which opens so that the gases can enter the exhaust system. Once they’re in the exhaust system, the level of toxicity in these gases is reduced by the catalytic converter. After that, the gases are finally released into the outside environment through the tailpipe.

On the downside, there is always a minor amount of toxic exhaust gases which do not get converted by the catalytic converter. During the combustion process, it is not uncommon for there to be a small pressure leak. This is when some toxic gases seep out from the chamber and end up in your crankcase (engine block). The pressure this adds to your engine could cause irreversible damage to it.

Basic Function

The PCV valve, which is short for the “Positive Crankcase Ventilation” valve, is a component of the crankcase ventilation system. This valve is designed to get rid of these toxic gases from your crankcase. That way, your engine can stay protected from them. Basically, the PCV valve uses a spring-loaded plunger to send gases in the crankcase area to the intake manifold. Once the gases reach the intake manifold, they are sent to the combustion cylinders for another ignition.

5 Common Symptoms

The PCV valve is an environmentally friendly component because it stops those extra toxic gases from making their way outside. Not only that, but they also create more fuel efficiency for your vehicle because your combustion chambers won’t need to burn as much fuel if the gases are getting burned in there too. This will save you money at the gas pump.

Of course, the PCV valve won’t always stay functional. There may come a point when the PCV valve finally breaks down. Watch out for the following 5 symptoms because they will likely indicate that you have a bad PCV valve if you experience them together.

1) Check Engine Light

If toxic gases are entering the engine block because the PCV valve is not doing its job properly, then this will cause the engine control unit to trigger the Check Engine warning light on the dashboard.

2) Oil Leak

A bad PCV valve increases the pressure of the engine block. As the pressure continues building up strong, an oil leak from the gaskets and seals is likely to follow.

3) Engine Stall

If the plunger of your PCV valve goes bad, it may stay open for too long. This will cause too much air to enter your combustion cylinders and give you a lean air-fuel mixture, which is when you have more air than fuel in the combustion mixture. This is a sure recipe for engine stalling.

4) Sludge

If leaky toxic gases reach the piston and cylinder wall components, then these gases will merge with the engine oil. This mixture will result in a sludge type of residue being formed. If enough sludge is generated, your engine could get damaged. Of course, you’ll have to inspect the oil in your engine to see the sludge up close.

5) Poor Fuel Economy

Since a functional PCV valve results in a good fuel economy, a bad PCV valve will result in a poor fuel economy. Suddenly, you’ll start paying more money at the pump. This should be a red flag right away.

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The Average Cost to Replace

When the PCV valve has finally gone bad and needs to be replaced, you’ll need to go to a professional auto shop to get this done. The replacement cost is usually anywhere from $80 to $105, plus added fees and taxes. This cost range includes the labor costs of anywhere from $60 to $80 and the parts costs of anywhere from $20 to $25. As you can see, this is not a lot of money for a replacement job. It should not take the auto mechanic more than an hour to complete this work for you.

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