2020 Subaru WRX Turbo Problems? DIY Vacuum Leak Fix

The Basics

A turbocharger problem is a failure or degradation of the forced induction system, which uses exhaust gases to compress intake air for increased engine power and efficiency. Issues range from mechanical failure of the turbo's internal components to supporting system failures that prevent it from operating correctly. Based on the analysis of owner reports, problems often stem from oil supply issues, foreign object damage, or failures in the interconnected intake and exhaust systems. A related diagnostic trouble code frequently mentioned is P0172 (System Too Rich), which can indicate an underlying issue affecting turbo operation, such as a boost leak or faulty sensor, rather than a direct turbo failure.

How It Manifests

Owners experiencing turbo problems report distinct symptoms that signal a loss of boost or mechanical distress. The most commonly reported manifestations from discussions include a significant loss of power, especially under acceleration where the turbo should be spooling. Many describe hearing unusual noises, such as a high-pitched whining or screaming under boost, or a siren-like sound, which often indicates compressor wheel damage. Others report excessive white or blue smoke from the exhaust, typically signaling oil being burned due to failing turbo seals. Instances of the engine entering a "limp mode" with a lit check engine light (often with code P0172) are also frequent, as the engine computer limits performance to prevent damage. Some owners note their vehicle simply fails to build boost, verified by a boost gauge reading zero or vacuum only.

Common Causes

Analysis of successful repairs points to several recurring root causes. The most prevalent is foreign object damage (FOD) to the compressor or turbine wheels, often caused by a failed air filter or debris entering the intake tract. Oil starvation or contamination is another critical cause, where delayed oil changes, clogged oil feed lines, or oil coking from excessive heat destroys the turbo's bearings. Boost and vacuum leaks in the intercooler piping, turbo inlet hose, or intake manifold gaskets are extremely common and can trigger related codes like P0172. Wastegate failure—either the actuator arm seizing or the internal flapper valve sticking—prevents proper boost control. Less frequently, issues arise from supporting modifications, such as an improperly tuned engine after installing parts like a Cobb cold air intake or turbo intake without supporting software, leading to unsafe air/fuel ratios.

Testing Procedures

Accurate diagnosis requires a systematic approach to isolate the issue. Start with a visual and auditory inspection: check for obvious oil leaks around the turbo center section, inspect the intake piping for damage, and listen for unusual whistling or grinding noises with the engine running. Perform a boost leak test by pressurizing the intake system (typically at the turbo inlet or intercooler pipe) with a tester and listening/feeling for leaks at all couplers, the throttle body, and the intercooler itself; this is a primary fix for many reported issues. Use an OBD-II scanner to check for stored codes like P0172 and monitor live data, particularly fuel trims and manifold absolute pressure (MAP) sensor readings. Inspect the turbo physically by removing the intake hose to check for shaft play (excessive in-and-out or side-to-side movement indicates bearing failure) and for damage to the compressor wheel fins. For suspected wastegate issues, manually check that the actuator arm moves freely.

Repair Options

Solutions should be attempted in order of cost and complexity, starting with the simplest.

1. Diagnose and Repair Boost/Vacuum Leaks: This is the most common and cost-effective fix. Based on numerous reports, reseating and tightening intercooler hoses, replacing cracked turbo inlet tubes, or fixing a leaking bypass valve often resolves power loss and code P0172 issues. Success rate for symptom resolution from these fixes is high.

2. Address Oil Supply Issues: If the turbo is failing due to lubrication problems, replace the oil feed line (which can become clogged) and ensure the oil drain line is clear. Always use high-quality, manufacturer-specified oil and change it at strict intervals. This repair can save a turbo showing early signs of seal failure.

3. Replace or Rebuild the Turbocharger: For confirmed mechanical failure (excessive shaft play, broken wheels), you have two options. A turbo rebuild kit can be a cost-effective DIY solution if the housing is undamaged, but requires mechanical skill. The more common solution is direct replacement with a new or quality remanufactured unit. This is the definitive fix for a failed turbo.

4. Correct Supporting System Failures: Ensure all related systems are functional. This includes verifying the operation of the mass airflow sensor, oxygen sensors, and the fuel system, as faults here can mimic or cause turbo-related issues like a rich condition (P0172). If performance modifications are installed, a proper professional tune may be necessary.

Real Owner Costs

Costs vary dramatically based on the repair path and whether labor is DIY or professional.

• DIY Boost Leak Repair: The cost is typically just for parts. A new silicone intercooler coupler set ranges from $50-$150. A replacement turbo inlet hose costs $100-$300. Labor is your own time.
• Professional Boost Leak Diagnosis/Repair: A shop will typically charge 1-2 hours of labor ($100-$250) plus parts.
• Turbo Replacement (Parts Only): A quality remanufactured turbo typically costs between $800 and $1,500 for most common applications. New OEM turbos can range from $1,500 to over $3,000.
• Turbo Replacement (Professional Labor): This is a significant job. Labor costs commonly range from $1,000 to $2,000 on top of the part cost, as it often requires removing significant components to access the turbo. Total shop bills for a turbo replacement frequently land between $2,500 and $5,000.
• Rebuild Kit: A basic rebuild kit (seals, bearings, piston ring) can cost $100-$300, but this does not include machining or balancing if needed.

Avoiding Future Issues

Preventative maintenance is key to turbo longevity. Adhere to strict oil change intervals using full-synthetic oil of the correct specification; this is the single most important practice. Regularly inspect the air intake system, ensuring the air filter is clean and properly seated, and all intake clamps are tight to prevent FOD and boost leaks. Allow for proper cool-down after hard driving by idling the engine for 30-60 seconds before shutting it off; this prevents oil from coking in the hot turbo center bearing. If installing performance modifications like a cold air intake or larger turbo inlet, invest in a proper professional tune to ensure the engine management system can accommodate the changes safely. Finally, address small problems immediately—a small boost leak or a minor oil seep can quickly lead to a major failure.

Source Summary: This analysis is based on 153 owner discussions from Reddit and automotive forums.