Engine “blow-by” is combustion gas that has seeped past the engine’s pistons and into the crankcase. Some blow-by is normal, but too much can harm the motor due to increased internal pressure.
Thankfully, the closed crankcase ventilation (CCV) system helps lower the pressure by dispersing it into the atmosphere or rerouting it back into the engine.
But first, it must be filtered.
What does a crankcase breather filter do?
A CCV filter, also known as a “breather” filter or oil separator, decontaminates blow-by before recycling it back through the engine. With time, CCV filters clog, restricting airflow and causing issues such as oil leaks, a high idle, and more.
In this guide, I’ll provide more details about breather filters, like how they work, signs of a problem, and replacement costs.
I’ll also answer some frequently asked questions about CCV filters, including:
- How often should you change your crankcase filter?
- What happens if you don’t change your CCV filter?
- Do I need a crankcase breather filter?
Let’s get started.
Table of ContentsShow
How A Crankcase Vent Filter Works
The purpose of the crankcase ventilation system is to manage pressure inside the crankcase and reduce exhaust emissions. The system is relatively simple, usually consisting of just a one-way valve, a tube, and a vacuum source.
When the pressure inside the crankcase gets too high, the system vents the excess blow-by through the positive crankcase ventilation (PCV) valve.
The blow-by then passes through the CCV filter/oil separator. The crankcase breather filter’s purpose is to remove dirt and other particles from the blow-by. Oil vapors are also extracted, collecting in the fiber mesh of the filter before returning to the oil sump.
Having been cleaned of toxins, what’s left of the blow-by is either dispersed into the atmosphere or recycled back through the engine via the exhaust gas recirculation (EGR) system.
4 Symptoms Of A Bad Crankcase Ventilation Filter
1. Excessively High Idle
If your engine is idling “high,” then the average crankshaft revolutions per minute (RPMs) have increased. This means the motor is working harder than it must.
This may stem from a blocked or clogged crankcase filter, restricting airflow inside the crankcase and creating a vacuum leak. Less airflow means the engine’s air-fuel mixture will be off, potentially leading to a higher-than-average idle.
2. Check Engine Light
As with many powertrain problems, if your crankcase breather filter goes bad, you’ll likely see a check engine light. The actual cause of the dashboard indicator wouldn’t be the filter itself but rather a result of it being clogged.
In this case, the most likely reason would be an improper air-fuel mixture inside the combustion chamber. This is also referred to as running rich (too much fuel) or running lean (too much air).
3. Oil Leaks
If blow-by isn’t vented from the crankcase, excess pressure can force motor oil through seals, gaskets, and even the engine air filter. Oil leaks are not only harmful to the environment, but too much oil loss can damage your engine.
A clogged CCV filter likely won’t result in a puddle of oil under your car. The leak would be most noticeable under the hood, near the air intake at the front of the vehicle.
4. Reduced Engine Performance
Another symptom of a blocked crankcase breather filter is reduced engine performance. Like a high idle and check engine light, poor performance stems from an imbalanced air-fuel mix.
If your car hesitates when stepping on the gas pedal, especially under heavy acceleration, you may need to replace your CCV filter. Other possible signs of a rich or lean combustion mix include smelling gasoline, poor fuel mileage, or engine misfires.
Crankcase Vent Filter Replacement Costs
Crankcase vent filters must be replaced and cannot be repaired. For parts, you’ll only need the replacement breather filter, which runs about $100 to $180 at any local or online auto parts store.
As for labor costs, most shops estimate the job at one hour, with rates ranging from $75 to $130 per hour. Rates depend on whether you go to a dealer or a smaller mechanics shop.
Using the above figures, the total cost of replacing a vehicle’s crankcase ventilation filter ranges from $175 to $310.
Replacing a CCV filter is relatively easy, so if you’re even a little mechanically inclined, you should be able to DIY the task.
Crankcase Vent Filter: FAQ
Generally, you should replace your car’s CCV filter every time you change the spark plugs.
This amounts to every 60,000 to 75,000 miles for the average vehicle, depending on its make and model. Check the owner’s manual to find out your car’s CCV filter replacement intervals.
Ignoring a clogged crankcase vent filter won’t cause any immediate failures, but it will put more strain on the engine.
Seals and gaskets will wear faster and be more susceptible to oil leaks. Moreover, fuel costs will increase as you’ll be getting fewer MPGs.
Yes, a CCV filter is required to account for excess blow-by causing increased crankcase pressure.
Interestingly, early vehicle designs simply had an orifice for venting the crankcase. This “open” design was eventually replaced due to excessive oil consumption issues.
Add CCV Filter Replacement To Your Routine Service Schedule
If you care for your vehicle and want it to last as long as possible, adding the CCV filter to your scheduled maintenance routine is crucial.
Ignoring a clogged breather filter just isn’t worth it. Not only will you shave years off your engine’s lifespan, but you’ll also pay more in service costs, get worse gas mileage, and poor performance.
Not sure what’s involved in a routine service schedule? Check out our detailed guide.
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