PCV stands for “positive crankcase ventilation.” The PCV valve is a one-way unit that attaches to the crankcase, which is where the vehicle stores its oil at the bottom of the engine.
As the engine burns fuel, it produces gases. Before emission controls were invented, the exhaust system released that byproduct to let it escape from the vehicle.
There are times when the gases get into the crankcase or pistons. If left uncontrolled, they mix with the motor oil to create sludge or less viscosity. The PCV valve helps them escape while breathers ensure the process works correctly.
You have the option to use a PCV valve with a breather or two breathers by themselves to manage those gases. Which option is the best to use?
PCV Valve and a Breather or Just Two Breathers?
The PCV valve does an excellent job of removing corrosive combustion and moisture byproducts from the oil. If the setup uses only two breathers, drivers must change the oil more frequently to prevent excessive sludge buildup.
If someone wants to run a PCV system, there’s nothing wrong with that decision. You’ll prolong oil life while trading off a little bit of the engine’s performance.
You lose some performance with a PCV valve and a breather because the valve is at its greatest opening when there is low vacuum available.
Even if you have a little at WOT, which you must if you have a carb signal, you’ll be sucking in the blow-by gases that reduce your performance.
It also makes sense to run two breathers instead of using a PCV system. Not only will you get a bit of extra performance under the hood with this setup, but you’ll also simplify what you’ve got going on under the hood.
When you run two breathers, your car will produce some extra pollution and have some sludge to manage.
As long as you get the oil changed on the recommended schedule and don’t run the engine too cold, you can minimize the issues and risks that sometimes develop with this setup.
Neither is really better than the other, so you’re just picking the preference you have for how you run things.
The PCV valve is a bit better for the environment, so you can say that you’re being socially responsible. The other provides some extra horsepower to deliver that rumble you want.
What Are Engine Breathers?
Engine breathers are pipes that let the engine vent its crankcase pressure away from the vehicle. It would be fair to call this component a venting pipe.
By venting the pressure out of the crankcase, the engine can have the piston rings seal tightly against the cylinder walls. This action delivers improved compression while reducing oil consumption, which is how extra horsepower gets generated.
Breathers are often attached to the valve cover. It incorporates a paper filter that catches oil blow-by that occurs to keep everything clean.
This component requires occasional inspection and eventual replacement if too much oil clogs its ability to function.
What Does the PCV Valve Do for the Engine?
A PCV valve is essentially responsible for controlling the emissions that a vehicle produces. It takes the crankcase gases and routes them back to the combustion chambers. That allows them to be burned safely without causing harm to the environment or the engine.
When the gases exit the crankcase from the PCV valve, the one-way nature of its design prevents them from returning to it. That stops sludge from developing in this space.
Some PCV valves can give an engine a small boost because they help the piston rings and crankcase improve compression, but it’s not the same lift that running two breathers creates.
If you decide to use a PCV valve with your setup, the component should be on your regularly scheduled inspection and maintenance checklist.
When Do I Need to Replace My PCV Valve?
There isn’t a set time to replace a PCV valve, so it’s a little different than changing your oil or replacing a battery. If it continues to function as expected, you won’t need to consider replacing the part.
As time passes, the exhaust gases that come through the PCV valve leave some oil traces that can eventually clog the area.
Here are some of the signs and symptoms that develop when your PCV valve is damaged or starting to go bad.
- The check engine warning light has turned on, or a warning message appears on your screen.
- You can start to hear whistling noises coming from the engine.
- There is a noticeable oil leak coming from the valve.
- You can see more sludge than normal around the engine during your inspection.
- A gasket or seal has blown while operating the vehicle.
The only way to check on the health of a PCV valve is to remove it from the engine. You’ll need to shake it to see if it can still function properly.
When you hear a metallic rattling sound coming from the unit as it opens and closes, it is likely working as expected. If you don’t hear any noise, the valve is probably sealed from unwanted deposits and requires a replacement.
How Long Does the Typical PCV Valve Last?
It is not unusual for a high-quality PCV valve to last the entire lifetime of a vehicle. As long as no obvious problems develop, there isn’t a need to change it out for a new one.
Some vehicles recommend that the PCV valve be replaced somewhere between 20,000 to 50,000 miles of driving. Your owner’s manual will outline the care recommendations in this area.
How to Replace a Bad PCV Valve
Vehicles with two breathers or no PCV valve won’t need to worry about replacing this component. By keeping the pipes and other parts clean and free of sludge, you can continue enjoying the HP boosts that come with your setup.
For those with a PCV valve, there may come a time when a replacement becomes necessary. Here are the steps to follow to help restore your engine’s functionality.
Please note that this is for informational purposes only, and all drivers should consult with their owner’s manual and any specific automaker instructions.
- Locate the PCV valve. It might be located near or on the intake manifold or on the valve cover. If there is a hose clamp, loosen it. That allows you to pull off the housing from the valve’s end.
- Remove the valve. Some are held in place with a simple rubber grommet, allowing them to be pulled free. It is more common to see it threaded. If it cannot be removed by hand, grab the base of it with a combination wrench or a crescent wrench of the appropriate size.
- Remove the hose and blow air through it. If it is dry, soft, brittle, spongy, or filled with sludge, it should be replaced. Some pipes develop hard deposits, and those should also get replaced. If you notice rusty clamps or deteriorated rubber, these items also require new parts.
- Check the PCV valve to see if it is faulty. If you shake it and hear a metallic sound, you might have another problem to find. When no noise is present, you can proceed to install the new component.
- If your new valve is threaded, screw it into place by hand to avoid stripping the valve cover’s threads. It should be securely seated, sticking out a little when you try to remove it. You don’t want to over-tighten the valve at this step.
- You can now reconnect the hose to the new PCV valve. Start the engine, check for leaks, and make adjustments as necessary.
Should I Run a PCV Valve with a Breather or Two Breathers?
The horsepower difference between a PCV valve-breather combo and running two breathers is minimal. Most drivers won’t need the extra boost, which means the emissions control benefits are better to have. If the engine is equipped with a racecar or high-performance vehicle, the HP gains could be helpful.
When you’ve never replaced a PCV valve before, the job can take an hour or two because finding it can be a challenge. I know – it took me about 45 minutes to finally find mine, even with the owner’s manual helping.
The other issue with a PCV valve is that it can stick. A threaded version benefits from a little lubricant in that situation.
Once you can start moving the valve around, it only takes about five minutes to pull out the old part and put in the new one.
PCV valves are an OEM product, so you’ll need to find the one meant for your make and model. Once you have the part, you can eliminate the signs and symptoms of a failing one and restore your engine’s performance.