Cars are complex machines with a plethora of technical components that you may not be aware of but which can significantly impact your vehicle’s driving qualities. The PCV valve is one of these components. The PCV valve ( positive crankcase ventilation ) allows gas to escape the crankcase. This helps the engine function more effectively while also preventing damage to the many gaskets and seals within it.
We’ll go over how a PCV valve works, the signs of a failed PCV valve, and how to deal with any PCV valve-related difficulties you might have in this article. It is also known as the positive crankshaft ventilation valve, is an important component of your engine’s pressure and airflow control system.
This modest, frequently neglected component boosts performance while lowering the chance of sludge accumulation and oil leaks. However, if the PCV stops working properly, it might result in various problems. Knowing the early warning signals of a faulty PCV valve and how to test it can save you money and prevent future engine damage.
- What Is A PCV Valve?
- Why Is It Important?
- How To Inspect?
- How Long Does It Last?
- When To Replace It?
What Is A PCV Valve, Exactly?
It is used to evacuate gas from the crankcase. You may be asking why this is necessary in the first place, so let’s go deeper. Waste gases are produced as a result of burning fuel in your engine. The majority of these gases, on the other hand, are expelled from the engine through your exhaust. Some may pass through your pistons and into your crankcase, where the engine oil is stored.
A thick, foul-smelling, greasy sludge forms whenever enough gas enters your crankcase and interacts with your engine oil. This sludge is bad for your engine since it can harm components and impede the system’s many oil channels. Your PCV valve is a one-way valve that allows all gases that enter your crankcase to return to your engine and be burned.
Because unburned fuel makes up around 70% of the waste gas departing your engine, redirecting the gases from your crankcase back into your engine is good. It not only helps to maintain the quality of your engine oil, but it also ensures that your engine runs more effectively.
Your PCV valve is usually located on top of the valve cover, which is easily accessible. Look for a small tube that connects your valve cover to your air intake; you should be able to find it easily.
It’s important to remember that, while most current automobiles come with a PCV valve, this isn’t true for every vehicle on the road. Before you spend too much time looking for this valve, check to see if your car has one.
What Is The Function Of The PCV Valve System?
When the moving elements of the engine churn the oil that lubricates the vehicle engine, pressure is created. Due to minor leakage during operation, valve guides and piston rings also produce pressure in the crankshaft. One of the duties of the PCV system is to regulate this pressure.
The system consists of an inlet hose that connects to the filtered air supply and delivers clean air to the engine. The air gathers up vapors and fumes as it passes past the engine. It then escapes through a second hose attached to the vacuum manifold. As air passes through the system, fumes from the crankshaft are drawn in, where they are burned safely in the engine.
During this procedure, a little vacuum is formed, which relieves any pressure that has built up. It controls airflow and prevents oil from being drained from the engine. The PCV system also extracts moisture from the oil. As the engine runs, heat is produced. Condensation forms as it cools and the moisture that results is absorbed by additives in the engine oil and held in suspension.
When the amount of moisture in the engine surpasses the capacity of the additives, the moisture attacks the metal parts of the engine, causing possibly substantial damage. The presence of a milky or foggy film in the PCV hose or valve indicates the presence of moisture in the system.
What Is The Significance Of A PCV Valve?
The purpose of this engine part is to reintroduce the gases into the circuit to be burned. The engine will eventually fail without it; also, if you’re driving fast, the gases inside the crankcase will build up pressure, producing damaged seals, blown gaskets, and oil leaks.
Symptoms Of A Bad PCV Valve
On the inside, most PCV valves are constructed of hard plastic, a hose, and a spring. They will wear down over time due to the harsh circumstances they are exposed to in your engine compartment.
Because the PCV valve is so important, you’ll notice several PCV valve symptoms that alert the driver to the valve’s condition when it starts to fail. Let’s take a quick look at these symptoms to see what you should do if you see any of them.
Your engine check light will start flashing on your dashboard, which is a classic indicator of a faulty PCV valve. When your engine light illuminates on your dashboard, error codes are recorded in your vehicle’s computer to alert you to a problem when you perform a PCV valve test or diagnosis. A good scan tool is required to diagnose and read the stored issue code. This indicator will not appear on PCV valves installed on some vintage cars that do not have an electronically regulated engine.
1. Rough Idling
Rough idling and higher engine rpm are two more common symptoms of a bad PCV valve. A vacuum leak caused by a pinched hose, collapsed or stretched hose or a clogged valve due to dirt and debris will produce rough idling. If you experience rough idling, it’s critical to test your PCV valve, which takes only a few minutes.
2. Unusual Engine Noises
Your engine may begin to make strange noises if either your PCV valve or valve hose malfunctions. From under your hood, you could hear a whirring or whistling noise. Air escaping from your valve or valve hose hole causes this noise. Keep an ear out for unusual engine noises, as they almost always suggest something is wrong.
3. Increased Oil Consumption
If the PCV valve or the hose that connects to it is clogged with moisture, the excess gas that is not getting out through the PCV valve will cause very high pressure inside the engine. When the pressure in your engine builds up, it will try to find a way to escape.
In the process of escaping through them, it may cause damage to the engine seals. If you see many oil leaks and increased oil usage, check the PCV valve and hose to make sure they aren’t clogged.
4. Hard To Accelerate
Due to the incorrect air-fuel combination, you’ll notice rough acceleration on idle, low-speed maneuvers, and even at high RPM if your PCV valve is defective or clogged. However, most new vehicles will not experience rough acceleration at high RPM due to a malfunctioning PCV valve, but it’s worth mentioning because it happens in most automobiles.
5. Lean Engine
Because the PCV valve regulates the intake manifold and the crankcase, a faulty PCV valve might result in a rich or lean engine due to an incorrect air-fuel combination. When your engine is running rich, you’ll notice a malfunctioning PCV valve symptom, white smoke from the exhaust tailpipe, and a gas smell (to learn more, check out our explainer on how to get gas smell off hands) from the smoke. A lean engine is difficult to identify because it causes misfiring.
6. Stalling Of The Engine
The plunger of your PCV valve may remain open if it fails. When this happens, a huge amount of air enters the combustion cylinders. Because there is more air inside the cylinders than fuel, resulting in a lean air/fuel mixture. As a result, your engine may stall or run poorly.
7. Engine Misfire
Because you can obtain a lean/rich air-fuel mixture ratio when the PCV valve clogs, you’ll get misfire while the engine is idling while traveling down the road. Your vehicle engine will misfire and run sluggishly if you have too much air or too much gasoline in the ratio.
8. Black Smoke From The Exhaust
When the PCV valve clogs, the crankcase will export oil to the combustion chamber. The oil will burn and exit through the exhaust valves as the spark plugs ignite the air-fuel mixture. Gray smoke will erupt from the exhaust tailpipe as a result.
Depending on what air-fuel combination the engine is receiving, if the PCV valve malfunctions and causes a lean/rich air-fuel mixture ratio, white/black smoke will appear from the exhaust tailpipe. If you notice a change in the exhaust smoke, check your PCV valve to make sure it’s working properly.
9. The Fuel Economy Is Poor
Your fuel efficiency may suffer if your PCV valve becomes jammed closed. This happens because your PCV valve permits some air into your engine when it’s open, which your engine control unit will take into account.
This helps the computer (ECU) adjust the air and fuel mixture properly. Insufficient air will reach the engine if your PCV valve is jammed closed, causing your system to operate efficiently. This affects your engine’s fuel efficiency and increases the amount of emissions it produces.
10. Filter Contamination
If your PCV valve breaks, oil and hydrocarbons may contaminate a filter known as a breather element. Water vapor is forced through your breather element by growing crankcase pressure. Water interacts with the gas, generating a buildup and perhaps enhancing your vehicle’s fuel economy.
One method of evaluating this component is to inspect it for buildup physically. Another option is to calculate the fuel economy of your vehicle. Your PCV valve may be failing if it starts to drop suddenly.
When you detect one or more of the aforementioned signs of a defective positive crankcase ventilation valve, it’s critical to inspect the component and determine what’s causing it to fail.
How To Inspect Your PCV Valve?
1. Examine The PCV Valve’s Grommets
The hoses attached to your valve and various fastening pieces may generate indicators of a broken PCV valve depending on how your valve is coupled to your engine. A flexible rubber grommet is often inserted into a slot in your valve cover to secure and seal your PCV valve.
On occasion, the valve may twist or screw into place and be sealed by an O-ring. Regardless of the setup, the PCV valve should be completely sealed to your engine at all times, meaning that any leakage is a problem. O-ring seals and rubber grommets stiffen and fracture or break with time due to their nature, resulting in oil leaks and allowing contaminants to enter your engine.
As a result, whenever you replace your positive crankcase ventilation valve, you should do so. As a precaution, you should also replace the O-rings or rubber grommets. Keep in mind that grommets come in various styles depending on your engine setup, so make sure you get the right one.
2. Inspect PCV Valve Hoses
PCV intake and output hoses are also prone to natural degradation. With time, they would tighten and maybe fracture or break. While your PCV system’s hoses are supposed to be oil-resistant, make sure they aren’t oil-saturated and bulging since this will prevent them from sealing properly.
Impurities could enter your engine through a leaking PCV inlet hose or outlet, causing the Check Engine Light to illuminate. Always use a high-quality brand valve hose when replacing PCV hoses. Installing the wrong PCV hoses will almost certainly result in sludge and oil leaks, as well as other PCV system difficulties.
3. Investigate The PCV
However, if none of these techniques work, look for and change your mesh filter as well. Continue with your positive crankcase ventilation valve if it’s still not enough.
4. Take A Look At The PCV Valve
The PCV valve must be inspected as the final stage. Pulling the PCV valve out of the valve cover grommet and disconnecting the rubber vacuum line are the most common ways to remove it. There will always be some rattling from a functional valve. Listen for the rattle when you shake your PCV valve. Your positive crankcase ventilation valve must be replaced if there is no sound.
5. Inspect For Moisture Contamination
Look for indicators of moisture contamination, such as a hazy or creamy coating on your PCV valve or its hose, while analyzing your PCV valve. The PCV valve must be replaced if there is moisture in the positive crankcase ventilation system.
On the other hand, moisture in your It is an indication of deeper problems, and simply replacing the valve will not address the problem; you must also replace the oil. Otherwise, the problem will continue to exist, and the symptoms will return.
Moisture accumulation is usually more severe when you drive your automobile on short journeys, less than 10 miles, needing more frequent oil changes. Along with oil changes, try to plan your errands so that each time you turn your key, you’re traveling for a longer period of time.
Additional engine problems could lead to moisture contamination if the moisture accumulation problem isn’t fixed. Moisture passes through your motor oil filter because it is a liquid. It’s one of the reasons why you should change your oil more frequently now. Another reason is that your engine does not have a chance to reach operating temperature when you make several short trips of less than ten miles.
This is crucial because after your engine is properly warmed up, the heat generated by its oil causes the additional moisture in your engine to boil. Your PCV system may remove the bulk of the moisture from your oil through steam if you drive long enough, usually around 20 minutes.
How To Evaluate The PCV Valve
If you’re having any of the issues listed above, it’s possible that your PCV valve has failed or has become stuck open. The issue, as previously stated, is that your diagnostic computer may not provide the exact information as to the origin of the problem. If none of the faults revealed by your engine check system is the issue, the PCV valve should be checked.
There is no one PCV valve test, but you may do a few things to see if it’s working properly. To do so, you must first locate the positive crankcase ventilation valve and the hoses that are connected to it. Begin your inspections by looking at the valve’s rubber parts.
If these are worn out, the component must be replaced. Next, locate and replace the mesh filter beneath the valve. Disconnect the hoses and inspect them if this does not solve your problem.
Before reconnecting and testing if the problem has been fixed, address any faults you notice here or replace the hoses if necessary. Remove the valve and give it a good shake as a final test. It’s time to replace the PCV valve if it isn’t rattling.
A PCV Valve’s Flow Must Be Tested
- Examine the PCV system’s components. As a result of exposure to tough engine conditions, inspect the PCV rubber grommet, O-ring, and hoses for symptoms of hardening, brittleness, or swelling. Replace any faulty components as needed.
- Remove the positive crankcase ventilation valve and hose gently, visually inspect them, and see if there is any slime on the PCV valve or hose. Clean the hose with cleaning solvent or WD 40, and replace the PCV valve. Both the appropriate component and the valve may need to be repaired.
- Most vehicles use a simple and inexpensive valve that costs less than $6, which should be replaced at every major service interval. Other high-end vehicles, on the other hand, feature PCV valves with heating chips and are more expensive. Whether your engine employs the positive crankcase ventilation valve with heating chips or not, always get a high-end valve.
- The PCV valve on some engines has a filter. Filters should be changed every 30k miles, according to some manufacturers.
PCV Vacuum Testing
- Start the engine and let it run for a few minutes until it reaches operating temperature.
- Disconnect it from the engine while leaving the hose attached; then cover the other side of the valve with your finger.
- The engine speed should reduce by roughly 40 – 80 RPM, and you’ll feel vacuum sucking at your fingertips.
- If the engine idles rough and the rpm drop exceeds 40 to 80, you most likely have a stuck open PCV valve.
- If you don’t feel suction at your fingertip, look for clogs in the valve and hoses.
- When you notice a damaged hose or a faulty valve, replace it immediately.
Other PCV Valve Testing Options
- Blocking or pinching the valve hose is another approach to check the positive crankcase ventilation valve. The hoses should return to normal after the engine speed drops by roughly 40-80 rpm. Look for a clogged or blocked PCV valve or a damaged vacuum hose if it doesn’t operate this way.
- On some automobiles, It may be located in a hidden location. Instead of going through the lengthy process of losing many other engine components, remove the motor oil dipstick and cover the dipstick opening tube with masking tape.
- Locate and remove the engine oil filler cap while the engine is idle. Then, using thin cardboard, cover the opening.
- Allow the engine to idle for one to two minutes while you stand back. Suction pressure should be dragging the masking tape against the dipstick hole (for some context, check out our guide on how to read oil level on dipstick). Otherwise, you’re dealing with a blocked PCV or a vacuum leak. Examine the hose condition, the rubber grommet, and the valve itself.
How Long Does A PCV Valve Last?
There is no straightforward answer to how long a PCV valve will last. You may extend the life of your car by performing routine maintenance, such as changing the oil. If you don’t do this and allow sludge, filth, and debris to build up in the oil, your positive crankcase ventilation valve’s lifespan will be drastically shortened.
At every important vehicle service, the valve is advised to be replaced. However, this does not imply that it cannot or will not fail between services. Knowing the signs and symptoms of a failing PCV valve is the best way to ensure that you can address the issue quickly and prevent further harm to your engine.
When Should You Replace Your PCV Valve?
In principle, It should survive eternally and should only need to be changed if it breaks. On the other hand, cleaning a clogged valve can return it to its original state. It’s actually rather simple to clean the valve; simply purchase some carburetor cleaner, pour it into a container, and soak the valve in it for a while.
Once the valve is clear of gunky deposits and has an even hue, it can be termed clean. If this doesn’t work, you’ll need to replace your old valve, which is, fortunately, a quite simple process. Simply remove the old valve from the cover, unhook it from its hose, and then replace it and reattach it.
Replace A PCV Valve: How Much Does It Cost?
Fortunately, replacing a bad positive crankcase ventilation valve is one of the cheapest car repairs. The part itself is usually between $20 and $50, and you can save money on labor if you do it yourself. Even if you buy the most expensive PCV valve and have your car serviced at a high-priced repair shop, you shouldn’t expect to pay more than $250 for a replacement at the most.
PCV Valve: Facts You Need to Know
- The PCV system is an emission control device that draws leftover combustion gases from the crankcase and routes them back into the engine via the intake manifold.
- A valve known as the PCV valve is the heart of most PCV systems, and its function is to regulate the flow of these gases.
- An old PCV valve that is no longer functioning like it should can cause performance and emissions problems.
- The result of a malfunctioning PCV valve could be a rough idle, sluggish acceleration, or increased oil consumption.
- Testing the PCV valve involves shaking it to check whether it’s functioning or not.
- A clogged hose or PCV system or inoperative valve can increase oil consumption, forcing oil past seals and gaskets.
- A leak in the PCV system can throw off the air-fuel mixture, triggering the check engine light.
- The PCV system should be inspected periodically, especially if engine performance has deteriorated.
- The PCV valve is relatively easy to test and replace.
- Replacing the PCV valve could eliminate the problems caused by a malfunctioning valve and make your vehicle run much smoother.
When you suspect a problem but aren’t sure what it is, take it to your trusted technician for an inspection. Keeping an eye on your it’s condition ensures that your engine runs at maximum efficiency, keeping you safe and saving you money.
Make sure you’re up to date on the indicators of a faulty PCV valve to get it fixed as soon as possible. The most common sign of a defective PCV valve is a malfunctioning sensor. As a result, it’s critical to regularly inspect your positive crankcase ventilation valve and other related components.
Finally, because most positive crankcase ventilation valves and related components are only worth $5 to $10, it’s worth checking and replacing them regularly to avoid costly repairs that could possibly harm your engine. We hope that this article helped identify your vehicle’s problem.