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 called a “breather” filter or oil separator, cleans blow-by before recycling it back in the engine. Over time, CCV filters can block, reducing airflow and causing problems like oil leaks, a high idle, and others.
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.
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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 goes through the CCV filter/oil separator. The crankcase breather filter’s aim is to eliminate dirt and other particles from the blow-by. Oil fumes are also removed, gathering in the fiber mesh of the filter before going back 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
Like most powertrain problems, if the crankcase breather filter becomes defective, you will probably notice an illuminated check engine light. However, the actual cause for the dashboard signal is not the filter but rather its obstruction.
In this situation, the possible cause is an incorrect mix of air and fuel in the engine. This is sometimes called running rich (a lot of fuel) or running lean (a lot of 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 indication of a obstructed crankcase breather filter is diminished engine performance. Similar to a excessive idle and check engine light, subpar performance stems from an unbalanced air-fuel blend.
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 expenses, 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.