Symptoms of a Bad or Failing Positive Crankcase Ventilation (PCV) Valve

The positive crankcase ventilation (PCV) valve works to evacuate gas from the crankcase of the engine. The PCV valve directs these gases back into the combustion chambers via the intake manifold. This plays a large role in engine efficiency, improving emissions and the overall operation of your vehicle. A bad PCV valve will affect the performance of your vehicle, so there are a few signs to watch out for before the valve completely fails:

1. Excessive oil consumption and leak

A bad PCV valve may have a leak, which will cause excessive oil consumption. In addition, you may also notice oil leaking through the seals and dripping on to the floor of your garage. This is because the pressure in the crankcase may increase when the PCV valve fails, so the oil is pushed out through the seals and gaskets since there's no other way for the pressure to be released. The leak will cause your vehicle to burn oil and leak oil beneath your vehicle. If you notice either of these, consult a professional mechanic to have your PCV valve replaced.

2. Contaminated filter

A filter called a breather element may become contaminated with hydrocarbons and oil once the PCV valve starts failing. This is due to the increased pressure building up in the crankcase, which pushes water vapor through the breather element. The water gets mixed with the gas, which causes the buildup and can increase fuel consumption in your vehicle. One way to check this part is to physically inspect the filter for buildup. Another way is to measure the gas mileage on your vehicle. If it starts to go down seemingly without reason, the PCV valve may be going bad.

3. Overall poor performance

As the PCV valve starts going bad, the performance of your vehicle will get worse. This can be exhibited by a buildup of pressure in the exhaust or the engine could stall out. The bad PCV valve may not close all the way, so oxygen may get into the combustion chamber. When this happens, the fuel and air mixture is diluted causing your vehicle to run poorly and lean out.

If you notice your vehicle is leaking oil, consuming large amounts of oil, you have a contaminated filter, or the car is not working like it should, have the PCV valve looked at and replaced. This will keep your vehicle running smoothly and keep your fuel economy where it should be. YourMechanic makes getting repairs to your positive crankcase ventilation valve easy by coming to your location to diagnose or fix issues. YourMechanic’s experienced technicians are also available for any questions that may arise. You can book a service online 24/7.


Next Step

Schedule Vehicle Engine Mechanical Inspection

The most popular service booked by readers of this article is Vehicle Engine Mechanical Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Vehicle Engine Mechanical Inspection reviews

Excellent Rating

(171,627)

Rating Summary
161,099
5,644
1,174
834
2,876
161,099
5,644
1,174
834
2,876

Rusty

23 years of experience
512 reviews
Rusty
23 years of experience
GMC Sonoma L4-2.2L - Vehicle Engine Mechanical Inspection - Arlington, Texas
Great overall impressions. Vechile is driveable and runs terrific now.
Honda CR-Z - Pre-purchase Car Inspection - Arlington, Texas
Does good work

Raymond

37 years of experience
402 reviews
Raymond
37 years of experience
Cadillac Brougham V8-5.7L - Vehicle Engine Mechanical - Las Vegas, Nevada
Talent and passion for what you do in any field is critical, Raymond seems to have both. I have dealt with many Mechanics in my day Raymond is one of the best. Thank you sir.

Corey

17 years of experience
332 reviews
Corey
17 years of experience
Dodge Durango V8-5.7L - Coolant is leaking - Davidson, North Carolina
Corey is fair and knowledgeable. Highly recommend.

Michael

36 years of experience
69 reviews
Michael
36 years of experience
Buick Verano L4-2.4L - Variable Valve Timing (VVT) Solenoid Replacement - San Antonio, Texas
Michael arrived early and got the job done quickly. My car is running so smoothly now. He answered all my questions, even the ones not directly related to the service he did. I will definitely request Michael for any future work. I highly recommend him!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

How to Replace an Air Diverter Valve
Car air diverter valves add clean air from the air pump to the emissions system to push out pollutants. Air valves are critical for car performance.
What is a Valve Cover all about?
How to replace a broken valve cover

Related questions

Hesitation while staring a 2000 Honda Civic
First thing you want to do on a Civic is check the valve lash. Check the adjustment for the mechanically adjustable valves. If the valves are off adjustment on Hondas they will do exactly what you are describing. The other...
Check Engine Light on after changing oil - 2012 Kia Rio5
If starting it today was the first time after changing your oil, the oil filter and oil galleries were empty for a few seconds. If this is the case, the Check Engine Light is reflecting the lack of oil pressure...
Can gasket cover leak. Can this make the car struggle or jump/ jerk when driving?
Hello. Yes, if the valve cover gasket is leaking, oil can leak down into the recesses where the spark plugs live, soak the rubber boots from the coil, and cause the plugs to misfire. If severe, considerable misfiring and stalling...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com