How much does it cost to replace your exhaust system?

Understanding your exhaust system

The combustion process produces toxic gases in your engine, not to mention a lot of heat and noise. It’s your exhaust system’s job to deal with all of this, so that your car can run safely, quietly, efficiently, and cleanly.

Performance-wise, the two key roles your exhaust system fulfils are controlling back pressure and maintaining exhaust gas flow:

• Back pressure is the resistance created when gases are being forced out of the engine. There needs to be some back pressure to help draw in air and fuel, but too much will force the engine to work harder to expel the gases, leaving it with less power for everything else.

• The exhaust gas flow makes sure that the gases leave the exhaust system smoothly and efficiently. If one or more of the system’s components are damaged or failing, this will create a buildup of gas that cannot leave the engine, affecting your car’s fuel efficiency.

Your exhaust system also helps to make your car cleaner and greener. Without it, your engine would be emitting noxious fumes into the atmosphere, which is bad not only for the environment, but also for the people who have to breathe them in.

How the exhaust’s components work together

• Exhaust manifold

  This collects the hot, harmful gases from all the engine cylinders, and funnels them into one pipe (the front pipe), which passes them to the catalytic converter.

• Catalytic converter

  This is where the gases are turned into less harmful emissions. Through a series of chemical reactions, the catalytic converter reduces toxic gases such as nitrogen oxides, and changes hydrocarbons and carbon monoxide (CO) into water (H₂O) and carbon dioxide (CO2).

• Diesel particulate filter (DPF)

  If you have a diesel car, you’ll also have a diesel particulate filter (DPF). This collects the soot and other particles from the diesel, and burns them off before they reach the tailpipe.

• Resonator

  The resonator’s job is to reduce high-pitched frequencies. It does this by using sound waves that cancel each other out, similar to noise-cancelling headphones. Not all cars have this component.

• Silencer/muffler

  Like the resonator, the silencer also reduces noise (specifically the exhaust gases escaping). If you’ve ever heard a car with a faulty or missing silencer or muffler, you’ll know how important this is in terms of noise pollution. It works by absorbing some of the sound waves that move through it. The resonator and silencer are part of the midsection.

• Sensors:

  There are sensors at various points throughout the exhaust system. Oxygen sensors check the oxygen levels in the exhaust gases, which helps the engine control unit (ECU) decide on the right air-to-fuel ratio to make the engine run more efficiently. There are generally two of these: one in the manifold and one near the silencer, but some vehicles have four.

  In addition to these main components, there are other parts, namely the exhaust hangers and flexible sections. The hangers attach the exhaust to your car while the flexible sections are included to allow for the movement generated by the engine’s vibration.

• Tailpipe

  The tailpipe is the final piece of the exhaust system; this is the one you see sticking out the back of the car. It takes the cleaned exhaust fumes and releases them into the air.

Signs your exhaust needs to be replaced

• Unusual sounds

  If your engine is rumbling, or is simply louder than usual, this could mean your silencer or exhaust pipes need checking. If the engine is hissing, you could have leaking pipes. A rattling sound, on the other hand, could indicate that your catalytic converter, or another exhaust system component is loose.

• Vibrations

  Vibrations could also be a sign that part of your exhaust system is loose. You’re likely to feel these in the steering wheel, the accelerator, or your seat. If your tailpipe is lower than usual, or even dragging along the road, you know it’s progressed from ‘loose’ to ‘falling off’.

• Smells

  If you can smell exhaust fumes inside your car, your exhaust system is leaking toxic gases into the air you’re breathing. This is incredibly dangerous, so you should not drive until your exhaust has been repaired or replaced. If the smell is more sulphurous (like rotten eggs), that’s an indication that your catalytic converter is damaged or failing.

• Smoke

  Look out for smoke coming from your tailpipe. A bit of steam is perfectly normal, but anything more is your cue to get your exhaust system checked. Depending on the colour of the smoke, there could be coolant, oil, or too much fuel in the system.

• Obvious damage

  Regularly inspect the visible parts of your exhaust system for signs of damage, such as rust, holes, and cracks. If you notice any of the above, you should get these parts replaced straight away, as they can cause leaks and other issues. Check your catalytic converter is still in place, too; thieves often target these because they contain precious metals.

• Fuel inefficiency

  A damaged exhaust can hurt your motor’s fuel efficiency. So, if you notice that you’re filling up at the petrol station more often than usual, this could be down to exhaust problems. Potential causes include a clogged exhaust, or a leak somewhere in the exhaust system. Both issues make the engine work harder, which increases fuel consumption.

• Lack of power

  Does your car have less power than usual (particularly when you’re accelerating), or are you having trouble starting it at all?

  This may indicate that your exhaust system isn’t working properly. As a result of this, the engine can’t get rid of gases efficiently, which negatively affects your car’s performance.

• Check engine light

  When the ‘check engine’ light illuminates, this can indicate numerous issues, such as a problem with the exhaust system, the catalytic converter, or the sensors. If this light appears, it’s worth getting your exhaust system checked out.

• Failed emissions test

  Your annual MOT will include an emissions test. If your car fails this test, that’s a sure sign that your exhaust system isn’t working as it should. This could be down to the catalytic converter and/or another component.

Common exhaust system issues

• Exhaust leaks: Often caused by rust and corrosion, exhaust leaks can also be down to loose connections or broken seals, the impact of road debris, or general wear and tear.

• Catalytic converter overheating: Various issues can cause the catalytic converter to overheat, including having the wrong air-fuel ratio, increased back pressure from a clogged exhaust, and engine misfires, which can lead to unburned fuel ending up in the exhaust system.

• Catalytic converter contamination: If oil, coolant or fuel additives get into the catalytic converter, it won’t work properly (and could even fail altogether).

• Silencer/muffler issues: Rust is one of the main causes of silencer/muffler problems. This part is exposed to both heat and moisture, which can quickly develop into rust if you don’t keep on top of it.

  Rust also spreads easily - and before you know it, you’ll be dealing with holes and cracks. Physical damage caused by driving (e.g. going over speed bumps, or being hit by road debris) is also a factor.

• Oxygen sensor malfunction: The most common issue with oxygen sensors is general wear and tear.

  They’re designed to last for around 30,000 to 100,000 miles, depending on how recently they were fitted. Modern oxygen sensors tend to last longer. Contaminated fuel and additives can also be a problem, along with faulty or damaged wiring.

How much does it cost to replace an exhaust?

The average cost for exhaust replacement in the UK is approximately £135, with typical costs ranging from £100 to £600.

The price you pay will depend on a variety of factors, including:

• Your car’s make and model.
• How much damage has been done.
• Which parts need to be replaced.
• How long the work takes.
• Local labour costs.

Where you live can affect the cost of a replacement exhaust. Generally speaking, if you’re based in a large city, it will set you back more than if you were in a rural area.

Average cost by vehicle manufacturer

• Vauxhall: £95 to £440
• Ford: £100 to £400
• Nissan: £105 to £535
• Volkswagen: £110 to £450
• Toyota: £110 to £500
• Honda: £140 to £490
• Audi: £190 to £550
• BMW: £200 to £600
• Mercedes-Benz: £210 to £650
• Land Rover: £275 to £700

Average cost by location

• Birmingham: £150 to £400
• Sheffield: £150 to £400
• Cardiff: £150 to £410
• Bristol: £155 to £415
• Manchester: £160 to £420
• Leeds: £160 to £420
• Glasgow: £170 to £430
• Edinburgh: £180 to £450

Repair vs. replacement

When you’re deciding whether to repair your car or replace your exhaust system, there are a few things to take into consideration:

• If the damage is only minor, (e.g. a small crack in one part of the exhaust) then repairing it is probably the best option. This is also advisable if your car is relatively old or in poor condition, as it wouldn’t make sense to put a brand-new exhaust into a motor that’s nearing the end of its life.

• Cost is also a factor. Repairing the exhaust, if feasible, is always going to be cheaper than replacement.

• However, whilst repairing is the cheapest option initially, you should also consider whether you’ll end up paying more in the long run. For example, if you have a part that’s been repaired several times, it may be better to simply replace it, rather than continue spending money on temporary fixes.

• If the damage is significant and your car isn’t too old, replacement is likely the best way to go, as this will add value when you decide to sell your car.

• You should also consider whether your exhaust system is in line with current emissions legislation. If it’s not, you should replace it with an upgraded one. Before you decide, consult a mechanic for a second opinion.

Repair vs. replacement (costs)

The cost of getting your exhaust system up and running again will depend on which part(s) need replacing or fixing. As a guide, here are some average costs for common exhaust repairs:

• Repair exhaust leaks: £75 to £200, depending on where the leak is, and how bad it is.
• Repair rust: £50 to £100, depending on how widespread it is.
• Repair cracks in the exhaust manifold: £200 to £1,000, depending on how bad the damage is.
• Clean and repair diesel particulate filter (DPF): £100 to £250, depending on how clogged it is, and whether the garage has the right tools available.
• Replace catalytic converter: £300 to £1,000, depending on whether you use an original equipment manufacturer (OEM) or generic part.
• Replace midsection: £300 to £500, depending on how many parts need to be replaced.