Bad Vent Oil Separator Symptoms

An excessive amount of smoke pouring out of your vehicle’s exhaust can be alarming. Though there are many factors that might be to blame, a faulty vent oil separator is one possible cause.

What Is an Oil Separator?

You might be wondering, “What does an oil separator even do?” The oil separator’s job was once handled solely by the positive crankcase ventilation (PCV) valve. Both parts operate to prevent oil mist from blow-by escaping into the atmosphere. Due to recent technological advancements and changes in the industry, compressions and engine temperatures have increased, leading to the increased popularity of oil separators. These days, it operates alongside the PCV in many vehicles.

The oil separator removes the oil from the crate case vapors and feeds it back into the system. It works by channeling the blow-by gases through a series of baffles or filters. This slows down the speed of the gases and lest the oil mist condense. The system can then collect the resulting oil droplets and return them to the crankcase.

In addition, the oil separator controls the flow of the oil and vapors by letting the vapors enter at specific times. It’ll also close the systems under certain engine loads.

Since the PCV system draws blowby from the crankcase, if there aren’t baffles or something similar to stop engine oil splatter from making it to the PCV valve to be ingested into the engine, then the engine might consume oil by drawing it through the PCV valve. So while there are some engines with easily replaceable oil separators, the ones with baffles in the valve cover that serve this purpose don’t usually need service for that reason.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Mid ‘80s Crown Victorias and Mustangs equipped with 5.0L engines have a metal PCV screen under the PCV valve and grommet that will clog over time and require replacement.

If you didn’t know that screen was there, you might wonder why so much oil was leaving the engine through the closure tube and crankcase filter. The screen can be annoying to remove, and some technicians will use a large sheet metal screw brazed or welded to an old screwdriver to extract it. If it’s removed and not replaced with a new screen, the engine will consume oil by drawing it through the PCV valve into the intake manifold.

The (metal PCV) screen can be annoying to remove, and some technicians will use a large sheet metal screw brazed or welded to an old screwdriver to extract it. If it’s removed and not replaced with a new screen, the engine will consume oil by drawing it through the PCV valve into the intake manifold.

–Richard McCuistian, ASE Certified Master Automobile Technician

Symptoms of a Bad Vent Oil Separator

When the oil separator is experiencing problems, you might observe the following symptoms:

Excessive Smoke

Although some amount of smoke coming from your vehicle’s exhaust is to be expected, an excessive amount is cause for concern. This can be a result of blow-by, which is a natural result of your engine’s pistons firing. Usually, the oil mist from blow-by is prevented from exiting the vehicle by the positive crankcase ventilation (PCV) valve and the oil separator. When one isn’t working properly, the oil mist can escape the vehicle’s system through the exhaust, causing plumes of smoke.

Certain vehicle models might also experience blue smoke coming out of the exhaust due to an outdated oil separator.

Burning Oil Smell

When oil mist escapes from the vent oil separator, it can burn up on components outside the PCV system such as the outside of the engine. This causes a burning oil smell. Even a small amount of burning oil can result in a strong smell, which can cause lightheadedness when inhaled.

Increased Oil Consumption

Since oil separators work to return the oil in blow-by to the oil sump, they reduce oil consumption. When an oil separator isn’t working properly, some of the oil that should be going back into the system might be lost instead, increasing oil consumption. You’ll notice the need to replace your oil more frequently in this case.

Check Engine Light

Your vehicle might notice a problem with your oil separator before you do. In this case, it’ll trigger the check engine light. Not all vehicles will be able to diagnose the exact problem with your oil separator though, resulting in a variety of stored faults. These might include codes for cylinder misfires, oxygen sensor/mixture adaptation faults, or even fuel trim faults.

Whistling Noise

A bad engine oil separator can also cause the crankcase vacuum to be higher than normal, which can cause a whistling or howling noise to erupt from your vehicle. If the problem is particularly bad, the sound can be likened to a freight train pulling up at the station.

Rough Idling

You’ll notice your vehicle is idling rough when it shakes and bounces while running. This will be accompanied by odd sounds and an inconsistent revolutions per minute (RPM) count. Since a bad oil separator tends to mess with the crankcase vacuum, a rough idle is to be expected.

Oil Gunk Build-Up

Trouble with your oil separator might also lead to oil caking around the different parts of your engine. These parts include the cylinder heads, cylinder walls, and piston rings This buildup can be dangerous for your engine and can result in a loss in engine performance if left unchecked.

Oil Separator Replacement Cost

Since a bad vent oil separator can cause a myriad of problems for your vehicle, it’s best to see a mechanic about a repair as soon as you can. Replacement oil separators sell for around $10 to $1,800.

Where to Get a Vent Oil Separator Replacement for Your Ride

A bad vent oil separator can cause a plethora of issues, so it’s best to solve the problem as soon as possible. CarParts.com has a selection of top-notch vent oil separators, so finding one for your ride should be quick and easy.

You don’t have to drive to different auto parts stores to find a compatible vent oil separator for your vehicle. All you have to do is use our vehicle selector tool to narrow down your options to the parts that are compatible with your specific make and model.

We source our products from reputable brands in the industry, so you don’t have to worry about quality. Our vent oil separators have all undergone strict quality checks during manufacturing to ensure they work like your factory unit.

Got some questions? Don’t hesitate to call our toll-free hotline, and we’ll be glad to assist you. 

Check out our vent oil separators, and order yours today!