Abnormal exhaust noise: causes

Abnormal exhaust noise (blowing, rattling, rumbling, engine sounding loud) often indicates a leak or damage in the exhaust system. Here are common causes and order of magnitude for costs.

Common causes

Hole or perforation in a silencer (rear, centre) or pipe: corrosion, impact. Joint between two sections leaking or burnt: blowing under acceleration. Bracket or clamp broken: exhaust moving or knocking under the car. Catalyst or DPF damaged (metallic noise, loose parts). Manifold or front pipe cracked (blowing from engine side).

What to do

Have the leak or damaged area located (when cold, visual check; sometimes at idle when hot). A large leak before the catalyst can let fumes into the cabin: ventilate and have it repaired urgently. Driving with a badly damaged exhaust may be illegal (noise, emissions) and worsen damage.

Order of magnitude for costs

Rear silencer: €150–500 and more (parts and fitting). Centre section: €100–400. Joint: €20–80. Catalyst: €300–1,500 and more depending on vehicle. My Auto Check-up helps you describe symptoms for an initial estimate before visiting the garage.