Signs Of A Bad PCV Valve (Overview Guide)

Signs Of A Bad PCV Valve (Overview Guide)

PCV Valve stands for Positive Crankcase Ventilation Valve.  It is an often overlooked part of the internal combustion engine system. To get a better understanding of this valve, its need, and function; a brief overview of how the internal combustion system works is necessary.

How the PCV System Works

The positive crankshaft ventilation system is a system where these gases called ‘blow-by’ are recycled and sent back to the cylinders for a second attempt at getting burnt. The crankcase houses oil at the bottom of the engine, and the PCV valve’s job is to reroute these gases back into the intake manifold system. By doing this, the PCV serves several important functions: reducing air pollution emissions and optimizing fuel usage.

The PCV valve functions during the idling phase of the car. During this phase, the pressure in the intake manifold is low and this allows for the blow-by gases to be sucked into the intake manifold for the second attempt at combustion. When your car speeds up, the pressure in the intake manifold increases, cutting off the supply of the blow-by gases. The PCV valve can then shut off to reduce the chance of the blow-by gases getting sucked back into the crankcase.

Symptoms of a Dysfunctional PCV Valve

What happens when the PCV malfunctions, and what signs should I look for? Courtesy of its functionality, the PCV valve ensures that there is no moisture in the crankcase. The presence of moisture in the crankcase can lead to the buildup of sludge. The hoses system connected to this system can also become coated with a thick film of milky oil sludge. This also leads to oil leaks and the corrosion of engine components.

Below are some symptoms of a faulty PCV:

Poor Fuel Consumption

If you discover that your vehicle consumes more than normal fuel, you should be wary because your PCV valve is building up faults. Depending on the engine capacity and size, your car’s fuel consumption range.

Misfiring While Idling

A vehicle with a faulty PCV valve will misfire when your vehicle idles. Misfiring can start as a nuisance but will grow into not making your engine start or stop altogether.

Oil Leaks Near the PCV

You will also notice leaking oil near the PCV if your PCV valve is getting bad. The leak can come small or big, depending on the level.

Increase in Internal Pressure

Internal pressure also increases as your car’s PCV valve becomes faulty. The crankcase pressure will increase considering that the intake manifold is subject to serious pressure, especially when your engine is turbocharged.   

Black Smoke

Black smoke is one of the symptoms car owners and drivers don’t like to see coming off their car’s exhaust pipe. But when you see this kind of symptom, quickly swing into action by looking at the PCV valve. It may have been faulty.  

Low Moaning Noise

Typically, your car’s moaning noise should be high, but when you notice it is getting low, be sure the PCV valve is bad.  

Clogged Air Filter

The airflow into and out of your car must be sufficient to improve your engine’s healthy performance. However, the air filter may get clogged, leading to a reduced airflow supply into your filter. When your PCV is faulty, the air filter will be unable to filter the air.

Mechanisms of an Internal Combustion Engine

The   IC engine is made up of cylinders and pistons. As air is taken via the depression of the pistons, the air mixes with fuel and is ignited by a spark plug. This ignition causes combustion which pushes the piston downwards. This continuous system of downwards and upwards movement of the pistons ultimately causes the gears to move giving rise to transmission or movement.

During the combustion phase, the burnt air-fuel mixture is pushed out and exits through the exhausts. However, a small portion of unburnt fuel and air mixture travels down with the pistons and exits through the pistons into the crankcase. Left unattended, it can cause a buildup of sludge.

Before 1964, this unburnt portion was allowed to waft through the system and exit through the exhaust back into the atmosphere. This became unacceptable and led to the manufacture of a positive crankshaft ventilation system. This was the first kind of automobile emission control.

How to Test A for a Bad PCV Valve

There is a way to hazard a guess as to if your PCV is still working. Although not foolproof, it is still worth the try.  Disconnect the PCV and shake. If you can hear the rattling of the plunger and spring inside of it, it is viable. However, if you hear no sound at all or a deep clunky sound, chances are it may have gone bad. It’s also good to look out for the appearance of obvious damage, oily film, and soot. These may also be indicators of damage. A can serve as a guide to the proper maintenance of your car.

Frequently Asked Questions

Q: Can you drive with a bad PCV valve?

Technically, yes. It is strongly discouraged. The buildup of gases and pressure might cause permanent damage.

Q: How long can a PCV valve last?

It all depends on usage and the quality of the material it is made of. Typically, a good PCV valve should last about 40,000 miles. However, its lifespan can be shorter and can cover shorter distance drives if it is not properly maintained or badly used.

Q: Can a PCV be fixed by a DIY means?

Yes. However, it is not recommended due to some technical requirements. It is advisable to hire the service of a specialist auto repairer. Otherwise, you may end up spending more than you budgeted in the first place.  

Final Thoughts

You may not have often found it on the maintenance list, but the PCV valve deserves just as much attention as other more common parts. Don’t forget that no part of your vehicle should be compromised in any way.