Exhaust repair and replacement

How to tell the exhaust is faulty

• The sound gets louder, rasps or hisses, especially when starting and accelerating. A small crack may only be heard with a cold engine, before the metal warms up and expands.
• There is a knock or a rattle from under the car over speed bumps or at idle. The cause is often a broken rubber hanger or a loose heat shield.
• The exhaust hangs lower than usual, the tailpipe is crooked or the pipe touches the ground.
• There is a smell of exhaust inside the car, especially at idle or when driving slowly.
• The engine warning light comes on. A leak in front of a lambda sensor can let air into the pipe and distort the sensor's reading.

The warning light has many other causes, so on its own it does not mean the fault is in the exhaust.

When the exhaust is repaired

There is no manufacturer interval for the exhaust. It is repaired when it leaks, has rusted through or its mounting has failed. How long a system lasts varies a lot. It depends on the material, road salt and how much the car is driven on short trips. A stainless steel system usually lasts clearly longer than one made of ordinary steel.

The exhaust is worth a look whenever the car is on the lift anyway, for example at a service. Surface rust does not yet mean a hole, and a silencer that looks sound from the outside can be eaten away inside. So we tap the pipe and move the joints and hangers by hand.

Weld or replace

Not everything is worth welding. A weld holds when the hole or crack is small and the metal around it is still sound. If rust has thinned the pipe over a wide area, the pipe soon gives way right next to the new weld. In that case we replace the damaged section. The usual solutions are:

• Welding, when the damage is small: a hole, a crack, a loose joint or a broken bracket.
• Replacing a section, when the rear silencer, the middle section or the front pipe has rusted through or thinned.
• Replacing hangers and brackets, when the pipe is sound but hangs low or knocks.

On many cars the system leaves the factory as one piece from the catalytic converter to the tailpipe. Then we cut out the damaged section and join the new one with a sleeve and clamp or by welding. The whole system does not have to be replaced just because it was made in one piece.

How the work is done

1. We lift the car and go through the system from the manifold to the tailpipe.
2. Where needed, we locate the leak with the engine running.
3. We tell you what we found: what can be welded, what has to be replaced and what the work costs. We start only once you have accepted the price.
4. We remove the damaged section. We undo or cut off any bolts that have seized with rust.
5. We weld the damage or fit the new section with new gaskets and clamps.
6. We hang the system on its hangers so that it touches neither the body nor the suspension.
7. We check the joints for leaks with the engine running and road test the car.

How long it takes

Replacing the rear silencer or the middle section of the system is usually less than an hour of work, when the joints come undone. How long welding takes depends on the size of the damage and how easy the spot is to reach. Replacing a catalytic converter usually takes from half an hour to about three hours, depending on the car. Bolts seized with rust add time to all of these jobs. If a part has to be ordered, we tell you when we agree the time.

What the price depends on

We do not publish a single price for exhaust repair, because the job can be one welded joint or half the system replaced. Replacing the rear silencer is a more bounded job, and it has its own estimate. The price depends on:

• Which part is damaged. The rear silencer is usually among the cheapest parts of the system, the catalytic converter and the particulate filter among the most expensive.
• Weld or replace. Welding is enough for small damage, but a thinned pipe has to be replaced.
• Parts. Original and aftermarket parts differ in price, and so do parts made of ordinary and of stainless steel.
• How the car is built. A twin exhaust has more parts, and on some cars underbody panels have to come off to reach the system.
• Rust. On a car driven on salted roads the flange bolts are often seized, and removing a broken bolt takes time.

We check the car and tell you the price before the work starts. If something else turns up during the repair, we call you before going on.

The exhaust and the inspection

At the inspection the exhaust is checked by eye and by ear. Under Traficom's inspection rules, a small leak and a wrongly directed tailpipe are minor faults, which earn a repair notice. The car fails, for example, for a clear leak, a missing catalytic converter, a non-compliant silencer or catalytic converter, or a mounting so poor that the pipe could come loose. An exhaust that is too loud earns a repair notice or a fail. On a petrol car the size of a leak is also judged in the emissions test, because air leaking into the pipe shows in the oxygen content of the exhaust gas.

According to Traficom's statistics, periodic inspections of passenger cars recorded 36 351 repair notices and 7 267 failing faults for the exhaust system in 2025. So there were five times as many repair notices.

A car with a repair notice passes, and nobody checks the repair afterwards. But rust keeps spreading from the edges of the hole, and the leak grows. By the next inspection it may already fail the car. The earlier a leak is repaired, the more often a weld or a single section is enough.

What you can check yourself

• Listen from behind and beside the car while someone else starts the cold engine. A rasping or hissing sound usually means a leak.
• Look from behind the car to see whether the pipe hangs low or the tailpipe is crooked.
• With the engine off and the pipe cooled down, move the tailpipe gently by hand. The hangers give a little, but a knock or a lot of play means a broken hanger or a loose joint.
• Note when the noise comes, and tell us. It speeds up finding the leak.

Do not touch the pipe while the engine is running or just after a drive, because it is hot. And do not go under the car if it is only on a jack.

When not to drive the car

A small leak at the rear of the system is usually no reason to leave the car standing, but it is a reason to book a time soon. Do not drive, however, if

• there is a smell of exhaust inside the car
• the exhaust has come loose and hangs or drags on the ground
• there is a burning smell from under the car.

Exhaust gas contains carbon monoxide, which cannot be smelled or seen. If you can smell exhaust inside the car, carbon monoxide is getting in too. A loose pipe can drop onto the road while driving, and a pipe dragging on the ground is damaged further. In that case it is safest to have the car towed to the workshop.