Does a Bad Catalytic Converter Make Noise?

Can a Failing Catalytic Converter Cause Noise?

Yes, a bad catalytic converter can make noise, depending on the type of damage. If the internal components break down or the outer shell is damaged, you may hear rattling, hissing, or excessive exhaust noise.

Common Noises from a Bad Catalytic Converter

Other Signs of a Bad Catalytic Converter

✅ Loss of Power – The engine struggles under load due to restricted exhaust flow.
✅ Check Engine Light (CEL) On – Common codes include P0420 (Catalyst Efficiency Below Threshold).
✅ Rotten Egg Smell – A sulfur-like odor indicates a failing converter.
✅ Overheating Under the Car – A severely clogged catalytic converter can glow red-hot.

What to Do If Your Catalytic Converter Is Making Noise

1. Inspect for Rattling Sounds – If you hear rattling when tapping on the converter, the internal honeycomb structure may be broken.
2. Check for Exhaust Leaks – Hissing or loud exhaust noises may indicate cracks or leaks in the converter.
3. Run a Diagnostic Scan – Check for P0420/P0430 codes, which indicate catalytic converter failure.
4. Replace the Catalytic Converter – If it’s severely clogged or rattling, replacement is the best option.

Final Thoughts

Yes, a bad catalytic converter can make noise, especially if the internal components are damaged or the converter is clogged or cracked. If you hear rattling, hissing, or loud exhaust sounds, it’s time to inspect and possibly replace the converter.

FAQs

1. What does a failing catalytic converter sound like?

It often makes a rattling, hissing, or loud exhaust noise, depending on the type of damage.

2. Can I drive with a rattling catalytic converter?

You can, but it’s not recommended—a failing converter can worsen over time and cause engine performance issues.

3. Why does a catalytic converter rattle?

The ceramic honeycomb inside breaks apart, causing loose fragments to rattle inside the shell.

4. How do I fix a noisy catalytic converter?

If the converter is rattling or clogged, replacement is the best option—repairs are rarely effective.

5. How much does it cost to replace a catalytic converter?

• Aftermarket catalytic converter: $200–$600
• OEM catalytic converter: $1,000–$2,500
• Labor costs: $100–$300

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