Exhaust system repair

The exhaust system — from engine to tailpipe

The exhaust system does far more than just route gases out of the engine. It consists of several components: the downpipe from the engine, the catalytic converter that turns harmful gases into CO₂ and water, possibly a particulate filter (DPF on diesel, GPF on newer petrol) that captures soot particles, lambda sensors that measure oxygen content, the mid-pipe and rear muffler that suppress noise, and finally the tailpipes. Each component has a function — a fault in one place affects performance, fuel economy, noise and emissions.

Symptoms of a bad exhaust system

The most common symptoms are increased noise (typically when accelerating), vibrations at low rpm, the check-engine light, reduced power and higher fuel consumption. Noises that change with engine speed are usually due to holes or cracks — a noise that starts suddenly typically means a pipe joint or coupling has split. Vibrations can come from broken hangers or destroyed mounts. When the check-engine light comes on with noises, it's often catalyst or lambda-sensor failure.

Catalytic converter and particulate filter

The catalytic converter contains precious metals (platinum, palladium, rhodium) and is a big cost when replaced. It wears out over 150,000–250,000 km, with the typical symptom being a check-engine light and a failed inspection. Theft of catalytic converters also happens — cars sit low enough that thieves can cut them out in minutes. On diesel, most cars from 2009 onward have a DPF (diesel particulate filter) that captures soot. The DPF normally regenerates while driving (passive regeneration at motorway speeds) or automatically (active regeneration at elevated temperature). If you only do short city trips, the filter can clog — we then perform a forced regeneration or manual clean. On newer petrol cars (from around 2018) the EU has also introduced GPFs (gasoline particulate filters) that work similarly.

Inspection and emissions

The exhaust system is critical in the EU inspection. Leaks, holes, a defective catalyst or tampered emissions result in a failed test. If your car is heading for inspection and you have noise or warning lights, we recommend a check with us first — we can carry out the necessary repairs and double-check that everything is in order before you go to the test.

Repair vs full replacement

Small holes in mufflers can often be welded locally, and pipe sections are replaced with pre-formed parts that we adapt on site. Where corrosion is extensive it pays to replace the entire pipe run. Catalysts cannot be "repaired" — they are sealed units replaced as a whole. On a moderately clogged DPF we can perform forced regeneration or chemical cleaning, but a fully ruined DPF must be replaced.

Book your repair online or call us on 41 17 32 24.