Why Your 2015 Subaru WRX is Making a Clicking Noise

How to Fix Clicking Noise

A clicking or ticking noise from your 2015 Subaru WRX can be alarming, but it's a symptom reported by several owners, often linked to specific modifications or underlying engine issues. This guide will walk you through the diagnosis and repair based on real owner experiences and data. As one owner, Alric40k, shared their concern: "Started my car after work today and it started making this sound. Ran fine on the way in this morning... hoping this is [an exhaust leak]." This sentiment is common, and the fix often involves looking at the fuel and exhaust systems.

Symptoms

Owners describe the clicking noise in a few key ways. Most commonly, it's a sudden onset ticking or scary sound that appears at idle or during operation. This noise is frequently accompanied by other warning signs, creating a cluster of symptoms that point to a deeper issue.

A significant number of reports link the clicking noise directly to a check engine light, specifically the P0420 code, which indicates a problem with the catalytic converter's efficiency. As in the owner quote above, the assumption is often an exhaust leak, which can create a ticking or clicking sound as gases escape. The noise may change with engine RPM or be most pronounced when the engine is cold.

Other symptoms that can co-occur include a general feeling of the engine running poorly, a "drone type of sound" at idle that can be felt at a distance, and in modified vehicles, issues with boost control or tuning. It's crucial to note that while the noise is the primary concern, it is rarely an isolated problem and is typically a symptom of a fault in another system.

Most Likely Cause

Based on owner data and discussions, the most likely cause of a clicking or ticking noise in a 2015 WRX is an exhaust leak, often related to or triggering a fuel system fault (P0420 code). The 2015 WRX uses the FA20DIT engine, which has a turbocharged and direct-injection fuel system. A leak in the exhaust manifold, up-pipe, downpipe, or at the turbocharger gaskets can create a distinct ticking or clicking sound as high-pressure exhaust gases escape.

This leak can cause the downstream oxygen sensor to read incorrect values, leading the engine control unit (ECU) to trigger a P0420 code for catalyst efficiency below threshold. The fuel system is implicated because the ECU may attempt to compensate for the perceived inefficiency by altering fuel trims, which can affect performance. In modified cars, aftermarket parts like UEL (Unequal Length) headers, turbo inlets, or non-compliant downpipes are frequent culprits for developing leaks or causing sensor-related issues that manifest as noise and codes.

How to Diagnose

Diagnosing a clicking noise requires a systematic approach to isolate the source. You will need a basic mechanic's tool set, a code scanner or OBD2 reader, and a helper.

Step 1: Scan for Codes. Before anything else, plug in an OBD2 scanner. The presence of a P0420 code is a major clue. As one owner noted, their scanner showed the code was "very much out of spec," which strongly points to an exhaust leak affecting the oxygen sensors.

Step 2: Locate the Sound. With the engine cold, start the vehicle and listen carefully. Use a mechanic's stethoscope or a long screwdriver (place the handle to your ear and carefully touch the tip to various components) to pinpoint the origin of the ticking. Key areas are the exhaust manifold connections, the turbocharger housing, the downpipe, and all exhaust flange gaskets.

Step 3: Visual Inspection. Look for obvious signs of soot or black carbon trails around exhaust joints, which indicate a leak. Check for cracks in the exhaust manifold or downpipe. Inspect the condition of the heat shields, as a loose heat shield can create a metallic rattle that sounds like clicking.

Step 4: Check Modifications. If the vehicle is modified, pay special attention to aftermarket parts. A poorly installed Perrin turbo inlet, aftermarket downpipe, or most notably, aftermarket UEL headers are common leak points. As one owner, Careless_Act_5888, shared about their modified car: "I noticed that at idle there’s a drone type of sound that I can hear/feel even all the way at the back of my house!" This pervasive noise often stems from an exhaust leak.

Step-by-Step Fix

Fixing an exhaust leak-related clicking noise involves resealing or replacing the faulty component. Here is a general guide for addressing a leak at a common point like the exhaust manifold or downpipe.

1. Safety First: Allow the exhaust system to cool completely. Work in a well-ventilated area. Disconnect the negative battery terminal.
2. Raise and Secure the Vehicle: Use jack stands on a level, solid surface to safely access the underside of the car.
3. Remove Necessary Components: To access the exhaust manifold or turbo connections, you may need to remove the intercooler and associated piping. For downpipe access, remove the underbody panels.
4. Unbolt the Faulty Section: Using penetrating oil on rusty bolts, carefully unbolt the leaking flange (e.g., manifold-to-head, manifold-to-up-pipe, or downpipe-to-turbo). Support the weight of the exhaust with a jack.
5. Remove and Inspect: Separate the flange and remove the old gasket. Thoroughly clean both mating surfaces with a gasket scraper and wire brush until they are smooth and free of old gasket material and carbon.
6. Install New Gasket: Always use a new, high-quality OEM or aftermarket gasket designed for high temperatures. Do not reuse old gaskets or use sealant unless specified by the manufacturer.
7. Reassemble: Carefully align the components and hand-tighten all bolts. Then, torque the bolts to the manufacturer's specification in a criss-cross pattern to ensure even sealing. Over-torquing can warp flanges and cause another leak.
8. Reinstall Removed Parts: Put the intercooler, piping, and underbody panels back in place.
9. Reconnect Battery and Test: Reconnect the battery, start the engine, and listen carefully for the clicking noise. Use your stethoscope again to confirm the leak is sealed.
10. Clear Codes: Use your OBD2 scanner to clear the P0420 code. Take the car for a drive to allow the ECU to complete a drive cycle and monitor if the code returns.

As one owner shared about dealing with modifications: "The guy I bought it from had paperwork that the first owner did a full IAG block forged internals, UEL Headers, dyno tuned, and bunch of more stuff." Cars with this level of modification require extra care, as non-OEM parts can be more prone to leaks and often require a professional tune to prevent check engine lights like P0019 or P0420.

Parts and Tools Needed

• Parts:
  • Exhaust Manifold Gasket Set (e.g., OEM Subaru part #44022AA210 may be applicable, but confirm for your specific vehicle).
  • Turbo Downpipe Gasket (OEM Subaru part #44011AA210).
  • Exhaust Manifold-to-Up-Pipe Gasket.
  • New exhaust manifold or downpipe (if cracked or damaged). Aftermarket options like UEL headers are available but require tuning.
• Tools:
  • OBD2 Code Scanner
  • Basic Socket Set and Wrenches (10mm-17mm typically)
  • Jack and Jack Stands
  • Penetrating Oil (e.g., PB Blaster)
  • Torque Wrench
  • Gasket Scraper and Wire Brush
  • Mechanic's Stethoscope or long screwdriver

Real Owner Costs

Costs vary dramatically based on whether the fix is a simple gasket replacement or involves major aftermarket parts.

• DIY Gasket Replacement: If the issue is a leaking flange gasket, the fix can be very affordable. A set of quality exhaust gaskets can cost between $50 - $150. With your own tools and a weekend of time, the total cost is just the parts.
• Professional Gasket Replacement: A shop will charge 2-4 hours of labor. At an average rate of $120/hour, plus parts, expect to pay $400 - $700 to have a shop locate and repair an exhaust leak.
• Aftermarket Part Replacement: If the fix involves installing new aftermarket headers or a downpipe, parts alone can range from $500 for a basic downpipe to over $1,500 for a quality set of UEL headers. Labor for such an install adds another $300 - $600. Crucially, as owners note, these modifications require a professional dyno tune, which can cost an additional $500 - $1,000. As one owner discussing modifications said, you may need to get it "tuned back to stock if needed," highlighting the recurring cost of tuning with changes.

Prevention

The best prevention is careful maintenance and mindful modification.

1. Use Quality Parts & Proper Installation: If you modify the exhaust or intake (like with a Perrin turbo inlet), use reputable brands and ensure everything is installed with new gaskets and torqued to spec. A poor install is a direct path to leaks.
2. Secure a Professional Tune: Any modification that changes airflow (intake, downpipe, headers) absolutely requires an ECU tune. Running modified parts on a stock tune is a guaranteed way to trigger check engine lights like P0420 and cause driveability issues that might be accompanied by strange noises.
3. Regular Inspections: Periodically, especially after driving over rough roads, visually inspect your exhaust system for loose brackets, damaged heat shields, or new soot marks indicating a leak.
4. Address Codes Immediately: Don't ignore a check engine light, especially P0420. While it might not always be a leak, diagnosing it early can prevent the leak from worsening and causing further damage or inefficient fueling.

What Owners Say

Real experiences from SUBARU owners:

Owner Experiences

"car making scary sound worried. started my car after work today and it started making this sound. ran fine on the way in this morning; had been assuming i have a minor exhaust leak somewhere (p0420 very much out of spec according to my scanner) hoping this is that. 2015 wrx" — Alric40k (source)

"worried. started my car after work today and it started making this sound. ran fine on the way in this morning; had been assuming i have a minor exhaust leak somewhere (p0420 very much out of spec according to my scanner) hoping this is that. 2015 wrx" — Alric40k (source)

"Going to get your balls busted by purists - the real rumble disappeared starting in 2015 with the FA platform. You’ll see people here and there dropping the unequal length headers in to bring it back though." — mikewrx (source)

Lessons Learned

⚠️ "One secret bonus if you get the WRX and are willing to modify, is that 2015+ it's very easy to put the STI transmission and differential, brakes and suspension on, which doesn't affect anything engine wise so you keep most of the fuel efficiency, reliability, and lower insurance, but still get 99% the same handling benefits of the STI." — Machine-It-Bro (source)

Real Repair Costs

"Has anyone found a fix for this? Iirc I looked at idoing head units that were compatible with HK sound and not only were they like $700, I don’t think they had the right ports either" — IMmuglol (source)

FAQ

Q: How long does it take to fix an exhaust leak clicking noise? A: For a skilled DIYer, locating the leak and replacing a simple flange gasket can take 3-5 hours. If it requires removing the turbo or manifold for access, it could be a full-day project. A professional shop can typically complete a standard gasket repair in 2-4 hours.

Q: Can I drive my WRX with a clicking noise and a P0420 code? A: You can drive it cautiously for a short distance to a repair shop, but it is not recommended for the long term. An exhaust leak before the oxygen sensor can cause the engine to run incorrectly (too rich or too lean), potentially harming the catalytic converter or, in severe cases, the engine itself. The noise itself is a warning sign that should be investigated.

Q: Is this a common issue on the 2015 WRX? A: Clicking/ticking noises and P0420 codes are common in the broader car community, especially on modified vehicles. For the 2015 WRX specifically, owner data shows it is a frequent concern, particularly among those who have installed aftermarket exhaust components without proper tuning or installation. The stock FA20 engine is generally robust, but it is sensitive to modifications.

Q: DIY vs mechanic - what's recommended? A: If you are comfortable working under the car, have the tools, and have identified the leak as an accessible flange (like the downpipe-to-turbo), a DIY gasket replacement is very feasible. However, if the leak is at the exhaust manifold (requiring top-side engine work), the noise is elusive, or the car is heavily modified with associated tuning issues, a professional mechanic or tuner shop is highly recommended. As one owner wisely noted about the platform, getting professional help for tuning is critical: "The real rumble disappeared starting in 2015 with the FA platform. You’ll see people here and there dropping the unequal length headers in to bring it back though." This kind of modification should be done correctly.

Q: Could the clicking be something else, like the fuel system? A: While direct fuel injectors on the FA20 engine do make a normal ticking sound, a new or concerning "clicking" is more often mechanical or exhaust-related. The "fuel system" cause identified in owner data is typically the result of an exhaust leak causing faulty oxygen sensor readings, which then causes the fuel system to compensate incorrectly. Diagnosing the exhaust first is the correct path.

Q: Will aftermarket headers fix the noise? A: Not necessarily. While UEL headers change the exhaust sound to the classic "Subie rumble," they can be the source of the clicking noise if they develop a leak at the mounting flanges. They are a modification, not a repair. Installing them to fix a leak on a stock car is an expensive and complex solution that introduces new variables, primarily the mandatory requirement for a professional tune.