Symptoms of a Bad or Failing Crankcase Vent Filter

Virtually all vehicles on the road today are equipped with internal combustion engines that have some sort of crankcase ventilation system. Internal combustion engines inherently have at least a small amount of blow by, which occurs when some of the gases formed during combustion escape past the piston rings and down into the engine’s crankcase. The crankcase ventilation system works to relieve any pressure from the engine’s crankcase attributed to blow by gases by rerouting the gases back into the engine’s intake manifold to be consumed by the engine. This is necessary, as excessive crankcase pressures can cause oil leaks to form if allowed to build too high.

The gases are usually routed through a PCV valve and sometimes a crankcase ventilation filter or breather filter. The crankcase ventilation filter is one of the only components of the crankcase ventilation system, and is therefore an important piece in maintaining the functionality of the system. The crankcase vent filter works the same way as any other filter. When the crankcase ventilation filter needs servicing, it will usually display a few symptoms that can alert the driver that attention is required.

1. Oil leaks

Oil leaks are one of the symptoms most commonly associated with a bad crankcase vent filter. The crankcase filter simply filters the blow by gases to make sure that they are clean before they are rerouted back into the vehicle’s intake manifold. Over time, the filter can get dirty and restrict the air flow, and therefore pressure relieving capacity of the system. If the pressure builds too high, it can cause gaskets and seals to blow causing oil leaks.

2. High idle

Another symptom of a potential problem with the crankcase vent filter is an excessively high idle. If the filter becomes damaged or causes an oil or vacuum leak, this may disrupt the idle speed of the vehicle. Usually a high idle is a potential indication of one or more problems.

3. Decrease in engine performance

A decrease in engine performance is another symptom of a potential problem with the crankcase vent filter. If the filter becomes clogged and causes any vacuum leaks, this may cause a decrease in engine performance due to the disturbance in the air-fuel ratio. The vehicle may experience a decrease in power and acceleration, especially at low engine speeds. These symptoms can also be caused by a variety of other problems as well, so having the vehicle properly diagnosed is highly recommended.

The crankcase filter is one of the few components of the crankcase ventilation system, and is therefore important in maintaining full functionality of the system. For this reason, if you suspect that your crankcase vent filter may be having an issue, have the vehicle serviced by a professional technician, such as one from YourMechanic. They will be able to replace your failing crankcase vent filter and perform any services that may be required for the vehicle.


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

(149,537)

Rating Summary
140,027
5,194
1,055
749
2,512
140,027
5,194
1,055
749
2,512

Rusty

23 years of experience
444 reviews
Rusty
23 years of experience
GMC Sonoma - Vehicle Engine Mechanical Inspection - Arlington, Texas
Great overall impressions. Vechile is driveable and runs terrific now.
Nissan Maxima - Alternator - Arlington, Texas
Very honest and informative. A fresh experience as far as mechanic-services go.

Raymond

37 years of experience
222 reviews
Raymond
37 years of experience
Cadillac Brougham - 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.

Chris

22 years of experience
2001 reviews
Chris
22 years of experience
Kia Optima - Oil Change - Winchester, California
Showed up early, friendly and and fast. Asked if there was anything else needed.

Dominic

28 years of experience
202 reviews
Dominic
28 years of experience
Ford Crown Victoria - Engine hesitates during acceleration - Port Charlotte, Florida
Showed up promptly, was professional and courteous, had diagnosis in no time.

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 Prep an Engine Block for Paint
When When you are rebuilding an engine, you’ll probably want to paint the engine block. It serves a few purposes including being clean and attractive in appearance, protecting from corrosion and rust, and offering a custom look, even matched with...
5 Commonly Overlooked Vehicle Maintenance Items
Brake fluid, auto transmission fluid, and coolant flushes, as well as cabin filter changes and valve adjustments, are all important services.
What Are the Benefits of Having an Engine Rebuilt Instead of Replaced?
Rebuilding a damaged engine may be a more economical option than full replacement. In an engine rebuild bearings, gaskets, and seals are replaced.

Related questions

Engine rattling, shaking and loss of power

The VANOS unit or solenoid can cause a rattling sound from the engine. The VANOS is a camshaft timing system which runs off of engine oil pressure. If the oil is the wrong viscosity or the system has a buildup...

Car will not start

If the vehicle is not restarting and there is no electrical power to the computer, then your automatic shutdown relay may be causing the problem. This relay is in the main engine relay box. If you are having a loss...

Water linking only into the passenger side soaking the carpet.

Hi, thanks for writing in. It sounds like you may have a clogged AC drain from debris. I recommend having the drain cleaned out from the engine compartment. If you would like help, consider having an expert automotive technician from...

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