Exhaust problems, fixed
without the guesswork.
Compare exhaust repair and replacement prices from trusted garages near you. Back boxes, catalytic converters, DPFs and full systems. Book online in 30 seconds, no upfront payment.
- Free to use
- No upfront payment
- Pay the garage directly
- Free cancellation
Find your price in 30 seconds
No upfront payment. Pay the garage directly.
More than just a pipe at the back of the car.
Your exhaust system does three separate jobs: it channels toxic combustion gases away from the cabin, reduces engine noise to legal levels, and cleans the emissions before they leave the tailpipe. Every section plays a part, and a failure in one area often puts extra strain on the rest of the system.
Starting at the engine, exhaust gases leave the cylinders through the exhaust manifold, which funnels them into a single downpipe. From there they pass through the catalytic converter (and the diesel particulate filter on diesel engines), which handle the emissions treatment. Next comes the centre section with its resonator, then the rear silencer (back box) and finally the tailpipe you can see at the back.
Threaded along the system are lambda sensors (also called oxygen sensors) that monitor gas composition and feed data to the engine management system. The whole lot is held in place by rubber hangers, metal brackets and clamp joints that let the system flex without cracking. In a UK climate, where road salt, rain and temperature swings take a constant toll on bare metal underneath the car, corrosion is the number one reason exhausts need attention.
Six parts that keep the system working.
Each section of the exhaust has a specific role. Understanding what they do helps you make sense of the quote when something needs replacing.
Catalytic converter
Bolted into the downpipe section, the cat converts toxic gases (carbon monoxide, nitrogen oxides, unburnt hydrocarbons) into less harmful emissions using a honeycomb structure coated in precious metals. It's the single most expensive exhaust component and a legal requirement on every petrol car built after 1992. Symptoms of a failing cat include a sulphur or rotten-egg smell, a rattling noise from underneath, and a check engine light triggered by the downstream lambda sensor.
Diesel particulate filter (DPF)
Fitted to almost every diesel sold in the UK since 2009, the DPF traps soot particles and periodically burns them off during a process called regeneration. Short trips at low speed prevent regen from completing, which clogs the filter and triggers a dashboard warning. A blocked DPF can put the engine into limp mode. Cleaning or forced regeneration at a garage often solves the problem, but a heavily damaged filter needs replacing.
Silencer and back box
The rear silencer (or back box) is the section you can see poking out at the back of the car. Its job is to muffle engine noise to legal levels. Because it sits low and at the rear, it's exposed to road spray, salt, and kerb strikes, making it the most common section to corrode through. A blowing back box is loud, annoying and will fail the MOT on noise alone. The good news: replacements are relatively cheap and quick to fit.
Exhaust manifold
The manifold bolts directly to the engine's cylinder head and collects exhaust gases from each cylinder into a single pipe. It endures extreme heat cycles (often exceeding 800 degrees C on petrol engines) and can crack over time, especially on turbocharged cars. A cracked manifold causes a ticking or hissing noise on cold start that sometimes quietens as the metal expands. It also lets unmetered air into the exhaust, which confuses the lambda sensor and triggers the engine management light.
Lambda sensors (O2 sensors)
Most modern cars have two lambda sensors: one before and one after the catalytic converter. They measure the oxygen content in the exhaust gases and feed that data back to the engine control unit (ECU), which adjusts the fuel mixture in real time. A failing lambda sensor shows up as poor fuel economy, rough idling, a check engine light, or an MOT emissions failure. They're a wear item with a typical lifespan of 60,000-100,000 miles.
Mountings and hangers
Rubber exhaust hangers and metal brackets suspend the entire system underneath the car, allowing it to flex with engine movement and absorb road vibration. When a hanger snaps or perishes, the exhaust drops and rattles against the underside of the car, often mistaken for a much bigger problem. Replacing a broken hanger is one of the cheapest exhaust repairs going, usually under £30 including labour.
Six signs your exhaust needs attention.
Most exhaust problems announce themselves well before a complete failure. Catching them early usually means a cheaper repair and a smoother MOT.
Loud rumbling or roaring
A deep rumble on acceleration usually means a corroded back box or a blown gasket between sections. It gets progressively louder as the hole grows.
Rattling underneath
A loose heat shield, broken hanger, or a deteriorating catalytic converter internals. Rattling that changes with engine speed points to the cat; rattling over bumps usually means a mounting issue.
Reduced fuel economy
A faulty lambda sensor or exhaust leak upstream of the sensor throws off the air/fuel ratio, and the ECU compensates by running rich. You'll burn more fuel and may smell petrol from the tailpipe.
Strong exhaust smell in the cabin
This is the one to take seriously. If exhaust fumes are reaching the interior, there's a leak forward of the cabin, possibly a cracked manifold or corroded downpipe. Carbon monoxide is colourless and odourless in pure form, but exhaust gases carry enough other compounds to produce a noticeable smell. Don't ignore it.
Visible rust or holes
If you can see brown corrosion, flaking metal, or daylight through the exhaust when you look underneath, it's only a matter of time before the section blows through completely. Road salt in the UK accelerates this significantly over winter.
MOT emissions failure
A failed emissions test often points back to the exhaust system: a blocked DPF, a tired catalytic converter, or a faulty lambda sensor. The garage will usually tell you which component is behind the reading.
When a weld is enough and when it isn't.
Not every exhaust problem means a brand-new section. A small hole in an otherwise solid pipe can often be welded or patched for under £50. A blown gasket between two sections is a straightforward replacement. And a snapped rubber hanger is one of the cheapest fixes in the garage.
Replacement becomes the better option when corrosion has thinned the metal to the point where a weld won't hold, when the catalytic converter's internal honeycomb has broken up, or when the DPF is too far gone for cleaning. A good garage will show you the damage on the ramp and explain why they're recommending a new part rather than a repair.
On the parts side, you'll often hear about pattern parts versus OE (original equipment). Pattern parts are made by third-party manufacturers to fit your vehicle. Quality brands like Klarius, Walker and BM Catalysts produce parts that meet type-approval standards at significantly lower prices than the car manufacturer's own branded part. For most everyday cars, a pattern exhaust is perfectly fine. OE parts are worth considering for newer vehicles still under manufacturer warranty, or for premium marques where the owner wants to maintain a full OE service history.
Weld or patch
Small holes in solid metal. Quick, cheap, and effective when the surrounding pipe is still in good shape.
Gasket swap
A blown gasket between sections causes a noisy blow. New gasket plus clamp and you're sorted.
Section replacement
When corrosion has eaten through a full section, fitting a new back box or centre pipe is cleaner and longer-lasting than multiple patches.
Full system
On high-mileage cars with corrosion across several sections, a cat-back or full system replacement can work out cheaper per year of use.
What the MOT tester is looking for.
The exhaust system features in several areas of the annual MOT inspection. Understanding what the tester checks can help you avoid a failure and the cost of a retest.
Emissions test
Petrol cars are tested for CO, CO2 and hydrocarbon levels at idle and at fast idle. Diesels face a smoke opacity test (the 'smoke meter'). The limits depend on your vehicle's age and fuel type. A tired catalytic converter, faulty lambda sensor, or blocked DPF will push readings outside the acceptable range.
Visual inspection
The tester checks the entire system from manifold to tailpipe for corrosion, holes, cracks, and missing sections. Any component that has deteriorated to the point where it could fall off or leak significantly is a fail. They'll also check that the catalytic converter and DPF (where required) are present and appear to be the correct type for the vehicle.
Leak check
The tester feels along joints, gaskets, and corroded areas for escaping gas while the engine is running. A significant exhaust leak at any point in the system is a major fault. Even a small blow that's clearly getting worse will likely earn an advisory.
Noise levels
While there's no decibel meter involved in the standard MOT, the tester makes a judgement on whether the exhaust is excessively noisy compared to the original system. A blown silencer, removed resonator, or aftermarket exhaust that's clearly louder than standard can result in a fail.
Mountings and security
Every hanger, bracket and clamp is checked. The exhaust must be securely attached to the vehicle with no excessive movement. A system hanging low enough to risk dragging on the road or contacting other components underneath is a fail.
If your exhaust fails the MOT, most garages can carry out the repair and retest on the same day. Leaving the car with the same garage for the repair means you can request a partial retest within 10 working days, which is typically free or discounted.
What you can expect to pay in the UK.
Exhaust repair costs depend on which section needs work, whether you go OE or pattern, and the labour rate at your chosen garage. The ranges below cover the majority of everyday cars. Premium, performance and older vehicles sometimes sit above these figures.
Prices reflect the total cost of the job. Enter your reg on YourGarage for an accurate quote from garages near you.
| Component | Typical range |
|---|---|
Back box / rear silencer The most commonly replaced section. Pattern parts are widely available and the job rarely takes more than an hour. | £100 - £250 |
Centre section / mid pipe Includes the resonator on some vehicles. Rust-prone due to road spray hitting the underside. | £120 - £300 |
Catalytic converter The precious metals inside drive the cost. Some specialist vehicles (hybrids, V6/V8 engines) sit at the top end. | £300 - £1,000+ |
Diesel particulate filter (DPF) Forced regen or chemical cleaning costs much less (£100-£250). Full replacement is the last resort. | £400 - £1,500+ |
Lambda sensor Sensors are a wear item. The upstream (pre-cat) sensor fails more often due to heat exposure. | £100 - £250 |
Exhaust manifold Labour is a big chunk of this cost because of the tight access. Cast iron manifolds on older cars are cheaper than stainless turbo manifolds. | £200 - £600 |
Full exhaust system (cat-back) Replacing everything from the catalytic converter back. Worthwhile on high-mileage vehicles where multiple sections are corroded. | £500 - £1,500 |
Prices are estimates based on independent garage rates for common UK vehicles. Actual quotes will vary by make, model and location.
Don't just fix the noise. Fix the price first.
Exhaust repairs vary wildly in cost between garages. The part might be the same, but labour rates, markup on parts, and whether the garage recommends OE or pattern can swing the total bill by hundreds of pounds.
Comparing quotes on BookMyGarage takes 30 seconds. Pop in your reg and postcode, pick the repair you need, and you'll see transparent prices from garages near you. No phone calls, no "we'll have a look and let you know" runaround.
Transparent pricing
See the total price before you book, so you know the cost upfront.
Trusted garages
BookMyGarage lists garages with real customer reviews. You can check ratings before you book.
Quality parts
OE-equivalent or OE parts from reputable brands. No mystery components from unknown suppliers.
MOT-ready
Need the exhaust sorted for an MOT? Book both together and save yourself a second trip.
Exhaust repair FAQs
- How do I know if my exhaust has a leak?
- The most common sign is a louder-than-usual rumble or hissing noise, especially on acceleration. You might also smell fumes inside the cabin, see black soot marks around exhaust joints, or notice the engine feels sluggish. If in doubt, a garage can put the car on a ramp and check in a few minutes.
- Can a damaged exhaust cause an MOT failure?
- Yes, and it's one of the more common reasons. The MOT checks for exhaust leaks, excessive noise, secure mountings and emissions within legal limits. A blowing gasket, corroded section or faulty lambda sensor can all cause a fail.
- Is it safe to drive with a damaged exhaust?
- It depends on the damage. A small blow from a corroded joint will get worse but probably won't leave you stranded. A cracked manifold or detached section is more serious because exhaust gases (including carbon monoxide) can enter the cabin. If you smell fumes inside the car, get it looked at the same day.
- How long does an exhaust repair usually take?
- A simple patch, clamp or gasket replacement can be done in under an hour. Replacing a full back box or centre section typically takes 1-2 hours. A catalytic converter or DPF replacement can take half a day depending on how accessible it is on your particular vehicle.
- What is a catalytic converter and why is it so expensive?
- The catalytic converter (or cat) sits in the exhaust system and converts harmful gases like carbon monoxide and nitrogen oxides into less harmful emissions. It contains precious metals like platinum, palladium and rhodium, which is why it's the most expensive single component in the system and also why cat theft has become such a problem.
- Do I need an OE exhaust or will a pattern part do?
- For most cars, a quality pattern part from a reputable manufacturer like Klarius, Walker or BM Catalysts will fit and perform identically to the original at a fraction of the cost. OE parts are worth considering for newer or premium vehicles where the warranty is still active or resale value is a priority.
- My diesel has a DPF warning light. What should I do?
- First, try a DPF regeneration drive: 20-30 minutes at steady speed (around 2,500 RPM in a lower gear) on an A-road or motorway. If the light stays on after that, the filter likely needs a forced regen at a garage using diagnostic equipment, or it may need cleaning or replacement if it's heavily blocked.
- Will removing my DPF or catalytic converter pass the MOT?
- No. Driving a car on the road without the DPF it was built with (for diesels registered after 2009) is an automatic MOT failure. Removing a catalytic converter from a car that was originally fitted with one is also an MOT failure and may constitute an offence under the Road Vehicles (Construction and Use) Regulations. Both are checked visually and via the emissions test.