Rattling Noise Under The Car
A rattle from underneath is often a loose heat shield, exhaust hanger or clamp; it can also be a broken catalytic converter or worn suspension parts.
Normal risk
Usually not urgent, but have it checked soon to avoid parts coming loose.
Short answer · What causes a rattle under the car?
Most often a heat shield on the exhaust has a rusted fastening and rattles at certain engine speeds. Loose exhaust hangers, a broken catalytic converter core and worn anti-roll bar links are other common causes. A workshop can usually find it quickly on a lift.
Safe checks you can do
- Note when it rattlesRattle at a certain engine speed points to the exhaust; rattle over bumps points to suspension.
- Tap the exhaust when coldWith the engine cold and off, gently tap the exhaust and shields to find loose parts.Never touch the exhaust after driving.
- Look for hanging partsCheck for anything hanging low under the car.
Questions that narrow it down
- Does it rattle at idle or at a certain rpm?Points to exhaust heat shields or the catalytic converter.
- Does it rattle over bumps?Points to suspension links or bushes.
- Is there a smell of rotten eggs or a check engine light?Can mean a damaged catalytic converter.
Possible causes
Listed without ranking. Use the questions above to see which ones fit your car.
- Loose heat shieldRusted fastenings let it vibrate.
- Worn exhaust hanger or clampThe exhaust moves and hits the body.
- Broken catalytic converter coreLoose pieces rattle inside the converter.
- Worn anti-roll bar links or bushesRattle over bumps.
Questions about Rattling Noise Under The Car
Is a loose heat shield dangerous?
Usually not, but a shield that falls off can no longer protect the floor from exhaust heat. Have it fixed.
How do I know if the catalytic converter is broken?
Tapping it can produce a rattle like loose stones. Often a catalyst code and reduced power come with it.