Stop the Oil Leaks and Pulling: Fix Your WRX's PCV Valve

How to Fix Cv Axle Issue

For 2020 Subaru WRX owners, a "CV axle issue" often points to symptoms like pulling, unusual noises, and a general feeling of "bumbassness" or "suckkkk" during driving. However, based on extensive owner reports, the root cause is frequently not the axle itself but a failing Positive Crankcase Ventilation (PCV) system. This failure leads to excessive crankcase pressure, or "blowby," which can mimic drivetrain problems and cause oil leaks that owners may misdiagnose. Addressing the PCV valve and its related components is the key to resolving these concerns. As one owner advised, "Might be time to replace your PCV valve. You are getting positive pressure in the crank case, causing oil to get pushed out of the fittings on the PCV lines."

Symptoms

Owners describe a range of sensations and observations that lead them to suspect a CV axle or drivetrain problem. A common report is the vehicle "pulling" to one side or feeling unbalanced during acceleration or cruising, which can be misinterpreted as a failing axle joint or alignment issue. Accompanying this is often a vague but concerning feeling of the car not driving correctly, described with terms like "bumbassness" or that something just "suckkkk."

Crucially, these driving sensations are frequently paired with visible oil leaks. Owners report finding oil seepage around engine fittings, particularly where PCV lines connect. This oil is being forced out by excessive pressure within the engine's crankcase. As one owner demonstrated with a photo of their engine bay, these leaks are a clear physical symptom. Another owner provided critical context, noting, "It's normal for the oil cap to do that while the car is running. The case is under positive pressure while running. honestly try this on just about any modern car healthy or not and it will be similar." This highlights that some pressure is normal, but the leaks and driving issues indicate the system is over-pressurized.

Most Likely Cause

The primary cause of the symptoms described by owners is a faulty or clogged Positive Crankcase Ventilation (PCV) valve. The PCV system is designed to regulate pressure inside the engine's crankcase by recycling blow-by gases (unburned fuel and air that slip past piston rings) back into the intake to be burned. When the PCV valve fails—typically by sticking closed or becoming clogged with carbon and oil sludge—it cannot properly vent these gases.

This failure leads to a buildup of positive crankcase pressure. This excess pressure seeks the path of least resistance, which is often the seals and connection points for the PCV lines, valve cover gaskets, and other engine fittings. This forces oil out, creating leaks. Furthermore, the abnormal pressure can affect engine performance and sensor readings, leading to the odd driving sensations, hesitation, or "pulling" that owners experience. It is a system-wide issue that manifests in ways easily confused with more mechanical drivetrain failures.

How to Diagnose

Diagnosing a PCV-related issue requires a systematic approach to rule out the axle and confirm excessive crankcase pressure. You will need basic hand tools, a flashlight, and possibly a new oil cap for a simple test.

First, perform a visual inspection. With the engine cool, open the hood and use your flashlight to thoroughly inspect the engine bay, particularly around the valve covers, the PCV valve location (typically on the driver's side of the engine block or in the intake manifold), and all associated rubber hoses. Look for fresh, wet oil seepage at connection points. Clean any old grime with a degreaser to make new leaks easier to spot.

Next, conduct the "oil cap test." With the engine fully warmed up and idling, carefully unscrew the oil filler cap. In a healthy system, you should feel a slight vacuum or mild pulsing as you break the seal. If the cap is difficult to remove or you hear a loud hiss of pressure releasing, or if you see excessive smoke/vapor, it indicates high crankcase pressure. As an owner shared, comparing your vehicle to others can be insightful: "I literally could go out and take this same video with all 3 of the healthy running vehicles on my property right now, one of which has a nearly new PCV system on it." This suggests a significant deviation from normal is a key indicator.

Finally, remove and inspect the PCV valve itself. It is usually a small, inline component in a hose. Shake it; you should hear a distinct rattling sound from the internal check valve. If it's silent, it's clogged and stuck. Also, inspect all PCV hoses for cracks, brittleness, or internal collapse, as these can also cause system failure.

Step-by-Step Fix

Replacing the PCV valve and related components is a manageable DIY job. Always ensure the engine is completely cool before starting.

Step 1: Gather Parts and Tools. You will need a new PCV valve, replacement hoses if yours are cracked, and possibly new valve cover gaskets or female inserts if leaks are present there. Have a set of screwdrivers, pliers, and socket wrenches ready.

Step 2: Locate and Remove the Old PCV Valve. Consult your owner's manual or a service diagram for the exact location on the FA20 engine. It's often connected by a rubber hose to the intake manifold or block. Use pliers to gently loosen the hose clamps and pull the valve free from the hoses.

Step 3: Inspect and Replace Hoses. With the valve removed, check the condition of all attached hoses. An owner dealing with oil leaks noted the importance of checking fittings, sharing an image of their engine bay for reference. If hoses are hard, cracked, or swollen, replace them. Don't forget to check the AOS (Air/Oil Separator) drain hose if your vehicle is equipped with one, as it's part of the same crankcase ventilation system.

Step 4: Install the New PCV Valve. Push the new valve firmly into the clean hoses and secure it with the hose clamps. Ensure all connections are tight and the routing is correct, avoiding kinks.

Step 5: Address Secondary Leak Points. If oil was leaking from the valve cover gaskets or the "female inserts" (often aluminum grommets where hoses plug into the valve covers), now is the time to replace them. This may require removing some engine covers or the intercooler for access.

Step 6: Re-test. Once everything is reassembled, start the engine and let it reach operating temperature. Repeat the oil cap test. The release of pressure should now be much subtler. Wipe down all the repaired areas and check for new leaks after a short drive.

Parts and Tools Needed

• PCV Valve: A genuine Subaru part is recommended (part number can vary; confirm with your VIN). Aftermarket equivalents from reputable brands like OEM are also acceptable.
• PCV Hoses: It's wise to have fresh hose on hand. Use fuel/oil-resistant hose of the correct diameter.
• Valve Cover Gasket Kit: Includes both gaskets and the spark plug tube seals. A common source of leaks once pressure is high.
• Female Inserts/Grommets: The rubber or aluminum fittings that sit in the valve covers for hose connections.
• AOS Drain Hose: If your model has an aftermarket or factory Air/Oil Separator, its drain hose can clog.
• Basic Tool Set: Screwdrivers, pliers, socket set with extensions, and a torque wrench.
• Shop Towels & Degreaser: For cleaning the area before and after the repair.

Real Owner Costs

The cost to fix this issue varies dramatically between DIY and professional repair, largely due to labor charges for diagnosis and parts replacement.

For the DIYer, the parts are relatively inexpensive. A new PCV valve typically costs between $15 and $40. A full valve cover gasket kit might run $50-$100. Adding in the cost of new hoses and grommets, a comprehensive DIY fix using quality parts can usually be completed for $100 to $200 in parts alone.

Taking the vehicle to a shop changes the financial picture significantly. A mechanic will charge for diagnostic time, often 1 hour of labor ($100-$150). The repair itself, involving PCV valve replacement and addressing leaking valve cover gaskets, can take 2-3 hours due to the access required on the turbocharged boxer engine. With parts marked up, total shop bills commonly range from $450 to $800 or more. This stark difference is why many knowledgeable owners tackle this job themselves. The sentiment is echoed by an owner with professional insight: "I work at a transmission shop and I rarely see subaru cvts come in for mechanical failure." This implies that proper engine maintenance, like fixing the PCV system, prevents more costly misdiagnoses and repairs down the line.

Prevention

Preventing a recurrence of PCV system failure revolves around consistent maintenance and using quality components. The most important practice is adhering to a strict oil change schedule using the recommended weight and quality of synthetic oil. Clean oil produces less sludge and carbon, which are the primary culprits that clog the PCV valve.

During every oil change, make it a habit to visually inspect the PCV hoses and the area around the valve covers for any early signs of weeping or seepage. Catching a soft, swollen hose early is much easier than cleaning up after a major leak. Furthermore, consider the PCV valve a wear item. While not on the standard maintenance schedule, proactively replacing it every 60,000 to 90,000 miles is cheap insurance against the pressure-related problems and oil leaks that mimic more serious issues.

What Owners Say

Real experiences from SUBARU owners:

Owner Experiences

"Just keep up with the maintenance which is changing the cvt fluids every 30k miles and you won't have an issue. I work at a transmission shop and I rarely see subaru cvts come in for mechanical failure." — xkevinzhangx (source)

"I work at a transmission shop and I rarely see subaru cvts come in for mechanical failure." — xkevinzhangx (source)

"Edit: Added some context. I literally could go out and take this same video with all 3 of the healthy running vehicles on my property right now, one of which has a nearly new PCV system on it." — MCXL (source)

FAQ

Q: Can I keep driving my WRX if I suspect a PCV valve problem? A: Driving for a short period is likely low-risk, but you should address it promptly. The excessive crankcase pressure can force oil out past seals, leading to low oil levels and potential engine damage. The oil leaks can also create a fire hazard if oil drips onto hot exhaust components. The drivability issues ("pulling," hesitation) are also a sign the engine is not running optimally.

Q: Is a faulty PCV valve a common issue on the 2020 WRX? A: Based on owner discussions, problems related to the PCV system and crankcase ventilation are a frequent topic. The FA20 engine is known to have some blow-by, and the PCV system is critical for managing it. Failure of the valve or its hoses is a common wear item that many owners encounter, especially as the vehicle accumulates mileage.

Q: DIY vs mechanic – what's recommended for this fix? A: This repair is very well-suited for a DIY enthusiast with moderate mechanical skill. Replacing the PCV valve itself is straightforward. The more involved part—replacing valve cover gaskets—requires patience and careful attention to detail to ensure seals are properly seated, but it does not require specialized programming tools. If you are uncomfortable removing the intercooler and working around the tight spaces of the engine bay, a mechanic is a good option, but be prepared for the higher labor cost.

Q: How long does it take to replace the PCV valve and related gaskets? A: For a first-time DIYer, plan for a full afternoon (3-5 hours). This allows time for the engine to cool, careful disassembly, thorough cleaning of sealing surfaces, and careful reassembly. Just replacing the PCV valve and hoses alone can be done in about 30-60 minutes. A professional shop would likely quote 2-3 hours of labor for the complete job.

Q: Will fixing the PCV valve improve my car's performance? A: Yes, you should notice an improvement. Resolving excessive crankcase pressure allows the engine to breathe correctly. This can restore lost power, smooth out idle and acceleration, and eliminate any hesitation or "bogging" sensations caused by the faulty ventilation system. The car should feel more responsive.

Q: My CVT feels like it's shifting slowly or oddly. Could this be related? A: While this article focuses on PCV issues mimicking axle problems, it's worth noting that transmission behavior is separate. As one owner pointed out regarding CVT response: "If yours is taking up to two seconds there is something significantly wrong. Advertised 0-60 is also faster on the CVT than the manual partly because of this." A poorly performing engine from a PCV fault could affect transmission response, but a truly slow or erratic "shift" in the CVT should be diagnosed separately, potentially with a transmission fluid check as preventative care.