Get to Know Your PCV Valve

Your PCV valve, or Positive Crankcase Ventilation valve, is a pollution control device that your engine uses to control moisture and gasses inside of your engine. The PCV valve is one of the most beneficial, and oldest pollution control devices used in engines today. The PCV valve also extends the life of the engine as well as the oil that lubricates it. The PCV valve is a simple device that requires very little maintenance. However, when the valve becomes clogged, you will notice that your engine does not run very well.

What Does a PCV Valve do?

The PCV valve sends partially burned gases that leaked into the crankcase back to the engine. Once these gases go back to the engine, they are burned along with the fresh air and fuel that normally enters the engine. The leaking of unburden gasses from the combustion chamber into the crankcase is a normal process. It is something that cannot be eliminated, but engineers always work to minimize it. Also, when you turn your engine off and allow it to cool, it collects moisture from the atmosphere and deposits it in the oil. The PCV valve helps to remove this moisture.

What happened to Engines Before the Invention of the PCV Valve?

The PCV valve was invented by General Motors and first used on production cars in 1963. Prior to that, the life span of an engine was relativity short. Engines burned fuel much less effectively than they do today. Without a way to actively vent moisture and partially burned gasses from the crankcase, engines would slowly turn the motor oil to sludge deposits. The process would combine the partially burned gasses, excess moisture, and some motor oil to form the sludge.

What Kind of Pollution Does the PCV Valve Help to Eliminate?

The pollution is in the form of hydrocarbons and particulate matter from partially burned fuel. Such partially burned fuel also has a strong odor. Today, cars emit very few odors compared to older cars. If you were to open your windows and drive behind an old car or truck, you will notice what such partially burned fuel smells like.

How does the PCV Valve Extend the Life of an Engine?

The PCV valve extends the life of an engine by actively moving moisture and partially burned gasses back in to the combustion chamber to be burned. If the gasses and the moisture are not returned to the engine to be burned, they will slowly combine with the oil to form sludge. The sludge deposits would eventually clog an oil passage in the engine and cause the engine to fail prematurely.

What are the Signs of a Faulty PCV Valve?

When the valve is dirty, it can stick open or closed. If the valve is stuck open, the engine can misfire at idle. This condition would also be considered an intake leak and cause the engine to run rough under all driving conditions. Engines can also begin to smoke because the valve that is stuck open is drawing a small about of engine oil out of the crankcase and into the combustion chamber to be burned. A valve that is stuck closed can also cause an engine to run rough because of the creation of sludge throughout the engine.

How do You Clean or Replace a PCV Valve?

Regardless of your decision to clean or replace your PCV valve, you will need to know where to locate it, and how to remove it. The easiest thing to do would be to check the user manual that came with the car. However, if you do not have the user manual, the valve is typically located on the top of the valve cover. The valve will either pull it out or you will need to twist and pull it out.

In most cases, you should replace a faulty PCV valve. Cleaning a PCV valve includes purchasing a can of carburetor cleaner. Since a can of carburetor cleaner is $5, and many PCV valves are only $10, it is not worth the $5 savings to clean your old valve. However, on some cars the valve can cost as much as $40, and it would be worthwhile to clean the old one. To clean it, spray the carburetor cleaner inside the PCV valve until you no longer see residue coming out.

As you can see, understanding your PCV valve, and what it does, is an important part of regular vehicle maintenance. Many times a problem with a rough running engine can be solved by cleaning, or replacing, the PCV valve. As part of regular maintenance, you should change the valve every 30,000 miles. When in doubt, it is always better to change the PCV valve than to clean it.