• 1exhaust manifold
• 2hanger
• 3flex pipe
• 4resonator
• 5catalytic converter
• 6muffler

Exhaust system noises

8 guides in this section

The exhaust makes the most recognisable sounds of all: the roar of a burnt-through muffler, banging when you lift off the throttle, a metallic rattle at particular engine speeds. Most of them do not affect how the car drives, but they should not be ignored either — behind a rattle that sounds harmless there is sometimes a broken catalytic converter, and its fragments can be drawn into the engine.

The section covers the whole path: from a penny heat shield and a torn flexible section to a burnt manifold and a blocked catalytic converter, including what each fault sounds like and the risk of exhaust getting into the cabin.

Where the noise comes from

exhaust system, along the floor to the rear

Narrow the sound down by questions

An interactive diagnosis tree: a few questions and the list of causes gets much shorter.

• Backfiring from the exhaust
• Rattling under the car

All articles in this section

• A broken catalytic converter: the sound A pouring rustle under the floor and a rattle at idle — how a collapsed catalytic converter ceramic sounds, how to check it and what it risks for the engine.
• Can you drive with a broken catalytic converter Collapsed converter ceramic rustles and chokes the engine. When you can drive to a workshop, when you cannot, and what it risks for the engine.
• How to find a rattling heat shield A metallic rattle in a narrow band of engine speeds is usually a loose heat shield. How to find it in ten minutes and how it is secured properly.
• Signs of a blocked catalytic converter A blocked converter chokes the engine: the car will not accelerate, stalls under load, uses more fuel. How to tell it from other causes of lost power.
• Signs of a rotten silencer The car has got louder, a rumble and popping come from under the floor, exhaust fumes reach the cabin — the signs of a rotten silencer and the repair.
• Signs of a torn exhaust flex pipe A sudden roar under your feet, vibration at idle and exhaust fumes in the cabin — how to recognise a torn flex pipe and what the repair involves.
• The exhaust has become louder: the causes A burnt-through silencer, a torn flex pipe, joints and gaskets: why the exhaust got louder, what it threatens and how the repair is decided.
• The exhaust roars when cold Why the exhaust roars after a cold start and quietens as it warms: manifold gasket, cracks, flex pipe. The checks and how the repair is decided.

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