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PCV Valve Replacement: When Should You Do It?

PCV Valve Replacement

The PCV or positive crankcase ventilation valve is an important part of most cars’ emission control systems. The PVC is known to be one of the earliest emission control devices equipped in cars. Its job is to take out leftover combustion gases from the crankcase and direct them back into the engine through the intake manifold. This way, the leftover gases will be burned in the combustion chamber rather than getting into the atmosphere through your tailpipe. The PCV system as a whole has no specific maintenance schedule, however, as the PCV valve ages, it can wear down and fail to function. When this happens, a PCV valve replacement is needed. If it fails to function and won’t open and close at appropriate times, it can cause slow acceleration, rough idle, misfiring, or poor fuel economy. You will know that your car is due for a PCV valve replacement if you experience any of the said signs.  

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PCV Valve Replacement: What Happens When the PCV Valve Goes Bad?


When a PCV valve becomes bad, it will trigger some issues that can only be corrected through a PCV valve replacement. But before we go through the problems that can happen when your PCV valve goes bad, we need to understand the basics. What is a PCV valve and what does it do? 


Your car has a crankcase found at the bottom of the engine and it holds the motor oil. When the engine burns fuel, it creates waste gases which are usually vented out through the car’s exhaust system. However, some of these waste gases can make their way past the pistons and into the crankcase. 


When this happens, the gases will mix with the motor oil and produce oil sludge. This oil sludge can damage the engine parts since it can lead to corrosion and can clog the engine passages. In some cases, the waste gases can lead to pressure building up inside the crankcase when the car is running at a high speed. It can cause problems since it could result in blown gaskets and damaged seals which can cause oil leaks. 


In the past, before emission-controlled devices were being used in cars, these waste gases were usually vented out into the atmosphere. But after laws had mandated that the waste gases should be captured again and not be released in the atmosphere, auto makers started to equip cars with PCV systems. The PCV system made it possible to recycle the waste gases into the air intake system, get mixed with the fuel and be directed to the engine to be burned. 


The PCV valve is an important part of the PCV system. It is a one way valve that is connected to the crankcase. It is where the waste gases exit the crankcase and ensure that they are not coming in again. 


A PCV valve replacement will be needed eventually since the PCV valve tends to fail over time. This is because the waste gases can leave deposits on the valve and can gum it up. A PCV valve replacement should be done from time to time, but it is often overlooked. This preventative maintenance will not cost you much but if not done, it can lead to a very costly problem. 


Now back to the question, what happens when the PCV valve goes bad? When it turns bad and needs a PCV valve replacement, you will usually experience signs or symptoms. It is important that you will be able to recognize them so you’ll know when to replace it. Keep in mind that when you notice any of the following symptoms, do not ignore it. Have it checked and replaced immediately since it can cause more serious damage. 


Here are the common symptoms of a bad PCV valve.

  • Lean or Rich fuel mixture


A faulty PCV valve can mess up the air and fuel mixture. It can cause the air and fuel mixture to become lean or rich. You will know that you have a rich mixture when you notice that your car has a slightly more gray or white smoke than usual or when you can smell fuel inside your car. Lean mixture on the other hand might trigger symptoms such as misfires, poor engine performance, or trouble starting the car. 


It is important that the moment you notice this symptom, have your car checked right away since it can also be caused by some other problems. 

  • Illuminating check engine light


Since a bad PCV valve that may call for a PCV valve replacement can cause either too much fuel or too much air to get into the engine’s combustion cylinders, the sensors monitoring this process will send this information to the ECU or engine control unit after the ignition of the air and fuel mixture. This sets off the check engine light to illuminate and alert the driver that there is a problem.


To find out what caused the check engine light to illuminate, you can use an OBD2 scanner and scan your car for any stored trouble codes. Trouble codes related to the PCV valve include P052E, P053A, P0171, or P0174.  

  • Oil leaks


A PCV valve operating as it’s supposed to lowers the pressure of the crankcase. However, when it becomes faulty, it can get stuck, making it no longer capable of opening or closing. When this happens, the pressure of the crankcase will build and the more pressure it builds, the higher the chance of oil leakage. 


If you notice that your seals and gaskets are leaking, have your car checked immediately and have a PCV valve replacement if needed. You may also want to check your air filter assembly since a bad PCV valve tends to cause oil to reach inside it. 

  • Engine stalling


If the plunger of the PCV valve malfunctions and it stays open, it can lead to an excessive amount of air to flow into the combustion cylinders. This causes a lean fuel and air mixture that can cause your engine to stall. 

  • Misfires


Like mentioned above, a lean fuel and air mixture can cause misfires. You may notice the misfires when you are idling or accelerating. Lean mixtures can cause your cylinders to not fire up properly. A faulty PCV valve can cause this problem and if you experience this symptom, do not ignore it and have it fixed immediately. 

  • Poor fuel economy


A rich fuel and air mixture in the combustion cylinders can be experienced when your faulty PCV valve stays closed and stuck. Since a rich mixture has more fuel than air, it translates to more fuel consumed or a decreased fuel economy. It can also lead to your engine producing more harmful gases that can cause failed emission tests. If you notice that you have to make several trips to the gasoline station than usual, you might have a bad PCV valve that requires a PCV valve replacement. 

  • Sludge


A bad PCV valve can no longer do its task, the waste gases from the combustion will begin to leak out into the middle of the cylinder wall and pistons. When this happens, these waste gases will be mixed with oil in the engine and produce a sludge residue. 


The sludge can damage the engine especially if the problem is ignored and it continues to build up. The problem with sludge, you won’t be able to know about it until you inspect your engine oil. You may also notice a ticking sound from your engine at times. 


PCV Valve Replacement: How Much Does it Cost to Replace a PCV Valve?


If you know your car is already due for a PCV valve replacement, you have to do it as soon as possible. If you wonder how much it costs, the PCV valve replacement can cost between $35 and $90. Its parts can be bought at around $25 while the labor costs are around $50 or more. 


If you are asking when you should have a PCV valve replacement, you can do so whenever you notice any of the symptoms listed above. There is no specific time frame on when you should have it replaced but as long as it is still working as it should, you can choose not to replace it yet. 


You can check your PCV valve to determine its condition. To do it, just follow these simple steps. 


  • Remove the PCV valve from the engine. You can usually spot it fastened on a valve cover at the end of a hose or tube found in your engine. 


  • Once the PCV valve is removed, shake it. If you hear a metallic rattling noise like it is opening or closing, then you have a valve that is functioning well. If it does not make any noise, it is an indication that there might be some gas deposits that have sealed it close. You may need a PCV valve replacement. 


If you want to do the PCV valve replacement yourself and save some money, you can if you know your way around cars. You just need to follow these steps. 


  • Find the PCV valve and loosen the hose clamp if your car has one. If it has no hose clamp, pull the small L-shaped housing off the valve’s end. 


  • Remove the PCV valve.


  • There are some PCV valves that are kept in place with a rubber grommet. You can just pull it free if your car has it. But if your car has a valve that is threaded, you can unscrew it by hand or by using a combination wrench or a crescent wrench.


  • Inspect the hose and the hose clamps or the grommet.


  • Detach the hose and blow through it. If you notice that the hose is dry, soft, brittle, or has sludge or hard deposits, get rid of it and replace the PCV valve hose with a new one. Replace the clamps too if they are corroded or if the grommet looks worn and deteriorated.


  • Position the new valve and screw it in. Once it screws into place, it is recommended that you screw it by hand. It is done to keep the threads in the valve cover from being stripped. You also need to ensure that the new PCV valve is seated securely and do not try to over tighten it. 


  • Reattach the hose to the new PCV valve


  • Turn the key in the ignition and start the engine.


  • Check the PCV valve and its surrounding area for any signs of leaks.  


PCV Valve Replacement: Can You Clean a PCV Valve? 


A bad PCV valve is usually caused by hard build ups and deposits. If you feel that cleaning it can fix the problem, you can. If it works, you might not need a PCV valve replacement anymore. To clean a PCV valve, you can clean it by soaking it in a solvent or carburetor cleaner, depending on what the auto supply store suggests.  


You can also try cleaning your PCV valve by spraying it with a WD-40. You don’t have to remove your PCV valve to do this method. You just need to disconnect the tube or hose from the crankcase and spray WD-40 into the tube. Make sure that you leave the tube up high so the WD-40 can reach the valve and clean the PCV. 


The methods in cleaning a PCV valve might be simple, but the experts are not recommending it. It is better to have a PCV valve replacement since cleaning a bad one will just be a temporary fix. Replacing it is not that expensive and it will only take you around 30 minutes to replace. 


The PCV valve plays a crucial role in the car’s emission control system. It helps keep the waste gases from being released into the atmosphere. If you notice any bad PCV valve symptoms, don’t ignore it. If your car is due for a PCV valve replacement, do it. If you refuse to correct the problem, it can damage your engine’s components which can be more expensive to fix. 

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