How to Fix an Exhaust Leak on Your 2020 Subaru WRX

Overview

Exhaust system problems on the Vehicle are a common complaint among owners, often manifesting as a persistent rattle, clunk, or knocking noise from the rear of the car. Based on analysis of 12 owner discussions, this issue is frequently misdiagnosed, as the symptoms can closely mimic failing suspension components. The root cause is typically traced to a specific design or wear point within the exhaust system itself, rather than the suspension, though the two systems are often investigated together due to their proximity and similar acoustic symptoms.

Symptoms Reported by Owners

Owners describe a distinct metallic noise originating from the rear of the vehicle. The symptoms are highly dependent on driving conditions:

• Driving Over Bumps: The most frequently reported symptom is a loud, jarring "clunk" or "bang" when traversing bumps, potholes, or uneven pavement.
• Low-Speed Maneuvers: A repetitive "knocking" or "rattling" sound is common during low-speed turns, acceleration from a stop, or when going over speed bumps.
• Idle or Startup: Some owners note a subtle rattle or buzz at idle or upon initial startup that may disappear once the exhaust heats up and expands.
• Symptom Confusion: In nearly all discussions, owners initially suspected failed rear struts, top hats/strut mounts, or other suspension components due to the nature of the noise. This highlights the importance of a thorough diagnosis before purchasing parts.

What Causes It

Analysis of confirmed fixes from the community points to two primary failure points, with one being overwhelmingly more common.

1. Exhaust Pipe Contact with Rear Crossmember/Body (Primary Cause): This is the culprit in the vast majority of reported cases. The exhaust system, particularly the mid-pipe or resonator, can make contact with the vehicle's rear crossmember or underbody. This occurs due to:

   • Failed or Sagging Exhaust Hangers: The rubber hangers that support the exhaust system degrade over time, losing tension and allowing the exhaust to drop and shift.
   • Heat Shield Interference: A loose or bent heat shield can drop onto the exhaust pipe or allow the pipe to contact it.
   • System Movement: Engine torque and suspension travel cause the entire exhaust to move; without proper clearance, contact is inevitable.

2. Worn Suspension Components (Less Common, but Often Suspected): While the noise is exhaust-related, genuine suspension issues can produce similar sounds. These include:

   • Worn Strut Top Mounts ("Top Hats"): These bearings can wear and create a knocking sound on bumps.
   • Failed Struts or Shocks: Internal valve failure can cause a clunking noise.
   • Loose Sway Bar End Links or Bushings.

Community data suggests starting the diagnosis with the exhaust system, as it is a more frequent and often less expensive fix than suspension work.

Step-by-Step Solutions

Follow this diagnostic and repair sequence, starting with the simplest and most cost-effective checks.

Step 1: Initial Inspection and Diagnosis

1. Safely raise and support the vehicle on jack stands on level ground.
2. Physical Exhaust Check: Grasp the exhaust pipe (mid-section and muffler) and attempt to shake it vigorously up/down and side-to-side. Look for excessive movement (more than 1/2 inch) and listen for any clunking. Visually trace the entire exhaust path, especially near the rear axle or crossmember, for shiny, polished spots indicating contact.
3. Heat Shield Inspection: Check all heat shields along the exhaust for looseness or areas where they may be bent into contact with the pipe.
4. Hanger Inspection: Examine every rubber exhaust hanger. Look for cracks, tears, or signs that the hanger has stretched and lost its shape.

Step 2: Adjust Exhaust Clearance (Most Common Fix)

If contact is found, the goal is to create permanent clearance.

1. Loosen Exhaust Clamps: Identify the exhaust clamp(s) near the point of contact (often near the resonator). Loosen them slightly—do not remove.
2. Reposition the Exhaust: With the clamps loose, have an assistant twist or lift the exhaust section to achieve at least 10-15mm (3/8-1/2 inch) of clearance from the contact point. Using a pry bar with a wood block to protect components can help.
3. Re-tighten Clamps: While holding the exhaust in the corrected position, re-tighten the clamps to manufacturer specifications (typically 25-35 ft-lbs). Use a torque wrench if possible.
4. Re-check Clearance: Ensure the exhaust cannot move back into contact when shaken.

Step 3: Replace Exhaust Hangers

If the hangers are visibly damaged or the exhaust sags significantly, replacement is necessary.

1. Purchase OEM or equivalent replacement hangers. Using a hanger with a slightly different design or durometer (stiffness) can help pull the exhaust into a better position.
2. Spray the metal hanger pins with penetrating oil.
3. Use a flathead screwdriver or dedicated hanger removal tool to pry the old rubber hangers off their pins. Install the new ones.
4. Re-check clearance as in Step 2 after installation.

Step 4: Inspect and Address Suspension (If Exhaust Checks Out)

If no exhaust contact is found, move to suspension.

1. Check Strut Top Mounts: With the car on the ground, have an assistant turn the steering wheel left/right while you listen near the top of the strut tower in the trunk/rear cabin area for knocking.
2. Check Sway Bar Links: Shake the rear sway bar. If the end links are loose or the bushings are cracked/worn, they will clunk.
3. Strut Test: Perform a standard bounce test on each rear corner. Push down firmly and release. The car should return to its normal height and stop. If it continues to bounce, the strut is likely failed.

Owner Feedback

The community emphasizes the importance of correct diagnosis. One owner stated, "I replaced both rear struts and top hats chasing a clunk. The noise was still there. Finally, I saw the resonator was hitting the crossmember. A 10-minute adjustment with a loose clamp fixed it." This experience was echoed in multiple discussions.

Another noted the value of a helper: "You really need to get under there and have someone shake the exhaust while you look. The contact point was obvious once we did that." For suspension-related noise, owners who found success replacing top hats reported the knock was more of a "hollow thud" directly correlated with steering input at low speeds, distinct from the sharper "clang" of exhaust contact.

What to Expect to Pay

Costs vary dramatically between DIY and professional repair, and hinge entirely on the correct diagnosis.

• DIY Cost (Exhaust Fix):

  • Adjustment Only: $0, if only loosening and re-positioning clamps is required.
  • New Exhaust Hangers: $15 - $50 for a set of 2-4 quality aftermarket or OEM rubber hangers.
  • Tools: Basic socket set, jack stands, and penetrating oil.

• Professional Shop Cost:

  • Diagnosis/Inspection Fee: $50 - $150 (often applied to repair).
  • Exhaust Adjustment/Re-hang: $75 - $200 for labor.
  • Strut Top Mount Replacement: $250 - $400 per side (parts and labor).
  • Complete Strut Assembly Replacement: $400 - $700 per side (parts and labor).

Recommendation: Given the data, invest time in a thorough DIY inspection of the exhaust system first. The potential savings over misdiagnosed suspension work is significant, often exceeding $500. If the exhaust is ruled out, then proceed to suspension diagnostics.

Source Summary: This analysis is based on 12 owner discussions from Reddit and automotive forums.