Your car’s exhaust system is one of the hardest-working components on the vehicle so it needs to be working properly. If your car seems to be struggling for performance, or is making some unusual noises, it’s possible that your exhaust could be broken.
A modern car exhaust system is much more than a simply chimney that takes gases from the engine to the outside world. It’s a crucial component for cleaning up harmful emissions coming out of the engine to reduce pollution. It can also help drive a turbocharger, by using the exhaust gases to spin a turbine that pushes more air into the engine to generate more power.
The exhaust on a passenger car will always exit right at the back of the vehicle to make sure that the fumes and gases are kept well away from the car’s cabin. This also keeps noise down inside the car.
However, the exhaust system quite vulnerable to damage. Being located on the underside of the car, a few centimetres from the road surface, means that it’s at the mercy of the elements and easily damaged by impact. That may be a direct damage from crunching over a speed hump, for example, or gradual corrosion from water and muck being splashed up from the road over a number of years.
As your car gets older, the chance of something failing within the exhaust system increases. If that happens, it will need fixing as soon as possible. You want a good system in working order to get the performance and fuel economy from your car, and the annual MOT test checks for noise readings and emissions levels. An exhaust system fault could end up returning you an expensive ‘fail’.
Ten signs that your exhaust could be broken
How do you know if your car has a problem with it’s exhaust? Here’s what to look and listen out for:
1. Rattle or vibration
If the exhaust pipe has come loose and is touching another part of the car’s underside, the chances are you’ll feel a vibration going through the vehicle.
This is often accompanied by an obvious rattling or buzzing noise, as metallic bits move around and hit other metallic bits at a high frequency.
2. Visible discolouring or damage
Older cars often have blackened exhaust tips, which is not necessarily a sign of a problem as it can be caused by years of hot exhaust gases exiting the system. Newer cars shouldn’t show this, however, so any visible discolouring at the tips or along the main exhaust pipe could indicate a problem.
Many modern cars actually have fake exhaust tips – either additional tips that are not conected to the rest of the exhaust system, or oversized and stylised holes that aren’t even exhaust tips at all – to make them look visually impressive. That means it can be harder to see the actual tip of the exhaust pipe where gases leave the vehicle.
3. Rumbling sound
One of the first signs that there could be something wrong somewhere along the exhaust pipe is a deep, low-down rumble – or maybe it sounds a bit like your car is blowing a raspberry to the rest of the world. That could signify a hole is developing, so some of exhaust gases are escaping through that hole rather than passing all the way to the end of the system.
4. Loud engine noise from the front of the car
If you’re getting a lot of noise from under the bonnet somewhere, it could mean a cracked manifold (the part where the gases come out of the engine and are collected into one pipe).
Alternatively, it coule be a worn gasket (a seal between different parts, usually between the engine block and the manifold).
If you’ve ever heard a car engine with no exhaust system attached to it, it’s unbelievably noisy as there’s nothing to direct and muffle the noise of hundreds of explosions going on inside the engine every second.
5. Loud engine noise from the rear of the car
Towards the rear of the car, just before the exhaust tip, is a box-shaped section called the silencer. As its name suggests, its job is to help muffle the noise of the engine.
Since it’s located right near the back of the underside of the car, it tends to be hit by dirt, water and debris flicked up from the road. That can easily lead to the silencer being damaged, which can result in a very noisy car.
6. Hissing noise
A hissing noise from underneath the car probable means there’s a leak somewhere, possibly through a crack in the exhaust manifold or in the pipework itself.
Unlike a hole, a crack may be very difficult to spot, especially if you’re looking at the car while it’s cold. As the metallic exhaust system heats up, it expands. This means that a crack may not appear until the engine is properly warmed up.
7. Muffled burbling
This could be cause by something that has broken off or come loose and that is now blocking the exhaust system. This can be quite dangerous as it can increase the gas pressure in the exhaust and lead to expensive (and explosive) breakages.
8. Catalytic converter
This is an important part of the exhaust system as it converts harmful gases associated with exhaust into more acceptable fumes. A catalytic converter (or ‘cat’) is usually a boxy section of the exhaust system located towards the middle of the exhaust pipe snaking its way under the car. They can be noisy when broken.
They’re also a target for thieves because they contain a lot of precious metals – and because the exhaust system hangs underneath the car, they’re easily accessible and quickly removable. If your car suddenly sounds louder and the noise is coming from around the middle of the car, check to see if there’s a big section of the exhaust missing.
9. Poor performance
An exhaust system is a part of the car’s entire engine make-up that you just can’t do without. If it’s worn out, loose or leaking, you will probably notice a difference in your car’s performance.
If your car seems to be struggling more than normal in everyday driving, it could be a problem in the exhaust system.
10. Decreased fuel economy
Fuel consumption tends to go hand-in-hand with performance. If your car is having to work harder than normal, it will also be using more fuel. If your exhaust is faulty, it can affect the fuel efficiency of your engine, which could mean greater use of petrol or diesel just to run it.
If your car seems to be using more fuel than normal, it could be a problem in the exhaust.
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