Symptoms
- Metallic rattling sound from the rear or underside of the car
- Often worse at idle or specific RPM ranges
- May get louder when accelerating
- Could be paired with a change in exhaust sound (louder/different tone)
Likely causes
- CommonLoose or broken exhaust hangerA failed rubber hanger lets the pipe sag and contact the body or frame.
- CommonLoose internal baffle inside the muffler or resonatorA broken baffle can rattle around inside the muffler, especially at certain RPMs.
- PossibleExhaust pipe rusted through with a loose sectionRust can weaken joints and clamps, letting sections rattle against each other.
- PossibleCatalytic converter internal substrate breaking apartA failing catalytic converter can rattle, especially when you shake the car or rev the engine.
- PossibleLoose clamp at a pipe jointA clamp that's worked loose over time lets two pipe sections rattle against each other.
What to do
- Visually inspect exhaust hangers along the length of the pipe for cracking, stretching, or complete failure.
- Gently shake the tailpipe by hand (with the engine off and cool) to see if you can feel or hear looseness.
- Rev the engine gently while parked (safely, away from anyone behind the car) to see if the rattle changes with RPM, which can suggest an internal baffle.
- Check exhaust pipe joints and clamps for looseness or visible rust-through.
- If you suspect the catalytic converter, a mechanic can check with a simple shake test or by tapping on it to listen for loose material inside.
- Replace a broken hanger, which is usually a quick and inexpensive fix.
- Have a muffler or exhaust shop replace a section with a rattling internal baffle, since these usually can't be repaired, only replaced.
- Address exhaust rattles reasonably promptly, since a hanging or dragging pipe can eventually create a bigger problem or a road hazard.
Tools and parts
- Flashlight
Exhaust hangerSearch: “exhaust hanger for [year make model]”
Muffler or resonatorSearch: “muffler for [year make model]”
When to call a pro
If you can't identify or reach the source, a muffler shop can quickly diagnose and repair loose hangers, clamps, or internal components.
Safety
Use caution
Only inspect the exhaust system when it's cool, since components get extremely hot during and after driving.