PCV Valve: Basic Function, Bad Symptoms and Replacement Cost

The Positive Crankcase Ventilation valve, better known as the PCV valve, is associated with the crankcase ventilation system. After the internal combustion process in the engine occurs, there are exhaust gases created which get redirected into the exhaust system by an exhaust valve. While in the exhaust system, the catalytic converter converts these toxic exhaust gases into less toxic gases. The gases are then released out of the tailpipe and into the outside air.

However, the catalytic converter is not able to convert all the exhaust gases that are produced from combustion. There are always going to be a small percentage of exhaust gases which seep out of the internal combustion chamber because of a minor pressure leak. These gases will flow toward the engine block (aka the crankcase) and end up in the middle of the cylinder wall and piston rings. If these gases were to remain in your engine block, it would create too much pressure there and ultimate cause your engine to get damaged.

Basic Function

The PCV valve is the component that prevents these toxic gases from staying in your engine block. The engine valve cover is where the PCV valve is located. There is a vacuum hose which links the intake manifold and PCV valve together. As the exhaust gases enter the engine block, the PCV valve contains a spring-loaded plunger which redirects the flow of the gases out of the crankcase and into the intake manifold. From there, the gases flow back into the combustion cylinders of the engine where they get ignited again during the next combustion process.

The Top 5 Symptoms of a Bad PCV Valve

If you want to have the cleanest emissions possible, you need to have a fully functional PCV valve. Unfortunately, PCV valves can go bad after they have been used for several years. You need to be able to recognize the symptoms of a bad PCV valve in your vehicle if you are going to replace it with a good one. Most of these symptoms are not too hard to recognize. Just make sure you don’t ignore these symptoms because your engine could end up with irreversible damage if you do.

Below are the top 5 symptoms of a bad PCV valve.

1) Oil Leakage

A functional PCV valve will work to lower the pressure of the crankcase. But when the PCV valve goes bad, it may not be able to get out of the closed position because it is stuck. This could happen if the valve gets clogged or just wears out over time. In any event, the pressure of the crankcase will build when this happens. The more pressure that builds, the higher the chance of an oil leak occurring. The seals and gaskets are where you can expect these leaks to occur. Sometimes the air cleaner assembly may have oil leaking into it as well.

2) Check Engine Light

The engine control unit is in constant communication with the oxygen sensors of your engine. When a PCV valve goes bad, it normally causes either too much fuel or too much air to enter the combustion cylinders of the engine. The sensors will relay this information back to the engine control unit after the air and fuel mixture is ignited. As a result, the Check Engine warning light will be illuminated on the dashboard.

3) Engine Stalling

The PCV valve has a plunger that could possibly stay open when it goes bad. If this happens, an excessive amount of air will flow into the combustion cylinders. This causes what is known as a lean mixture of air and fuel because there is more air than fuel in the cylinders. The result of this will be engine stalling or rough idling.

4) Bad Fuel Economy

If your PCV valve remains closed, it will cause a rich mixture of air and fuel in your combustion cylinders. This means there is more fuel than air in the cylinders. Since more fuel is being consumed, it damages your fuel economy and forces you to pay more money for gas. On top of that, your engine will produce more emissions as well.

5) Sludge

When those toxic gases from the combustion start leaking out into the middle of the cylinder wall and piston, they will mix with the oil in the engine. When oil and exhaust gases merge, it creates a sludge residue. This sludge will continue to build up until it ultimately damages your engine. You won’t notice the sludge until you inspect your engine oil and notice the sludge for yourself.

Read also: Trouble Code: P2096 (Post Catalyst Fuel Trim System Too Lean Bank 1)

Replacement Cost

You will be happy to know that replacing a PCV valve will not cost you too much money. The average replacement cost for a PCV valve is anywhere from $35 to $75. The part itself only costs around $10 or $15. If you know how to replace the valve yourself, you could cut out the labor costs altogether and only pay $10 or $15 for the replacement. Otherwise, an auto mechanic will charge you between $25 and $60 to perform the replacement job for you. This isn’t a whole lot of money as far as auto jobs go, but it is certainly more than the cost of the PCV valve part. If you are not skilled in the field of auto mechanics, then you should pay the labor costs and have a professional do the job properly for you.

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