Exhaust problems are a nightmare. They're stressful, they're scary and, if you're not careful, they're expensive as well. When you notice that something is wrong, you need the solution fast. But there are so many common exhaust problems and you can find yourself wading through a sea of information to find the right answer.
Sometimes, you can't even find it.
That's why we've put together this guide of frequently asked questions about common exhaust problems. We've answered nine of the most pressing problems all in one place, and you can use the table of contents below to jump straight to the one you need.
Each answer covers:
- What the problem is
- The symptoms of your issue
- What your next steps should be
We've also provided our number one tip for solving any of these problems as soon as possible, so make sure you read all the way to the end.
So, what are we waiting for?
- Why is There Blue Smoke Coming From My Exhaust When Accelerating?
- Why is There White Smoke Coming From My Exhaust When Accelerating?
- Why is There Black Smoke Coming From My Exhaust When Accelerating?
- Why is There Grey Smoke Coming From My Exhaust When Accelerating?
- Why Does My Exhaust Rattle When Accelerating?
- What Causes a Noisy Car Exhaust?
- Why Can I Smell Exhaust Fumes?
- How Do I Find an Exhaust Leak?
- What Should I Do If My Exhaust Has Fallen Off?
- How Do I Solve Any Of These Common Exhaust Problems?
Why is There Blue Smoke Coming From My Exhaust When Accelerating?
If you notice blue smoke coming from your exhaust when you are accelerating or idling, then there can be several possible reasons for this:
- Worn valve seals or piston rings (usually in cars with a high mileage)
- Too much oil in the system
- Oil spilt on the exhaust during a service
- Worn-out turbocharger
- Bad glow plugs (diesel cars only)
Blue smoke can be a sign of oil burning with fuel in the combustion chamber due to a leak in the engine valve seals. Blue smoke that appears when accelerating can be the result of an issue with the Positive Crankcase Ventilation valve (PCV). If the PCV is not working properly, oil, air, and gases will continue to mix, and the blue smoke will continue to leave your exhaust.
As there are multiple valve seals in your vehicle, you must have this checked out by a mechanic so that they can figure out which one is causing the issue.
For diesel cars, a bad glow plug can cause blue smoke. Blue smoke can even be caused by oil escaping from an improperly sealed gasket and dropping onto the hot exhaust parts of the drivetrain - this will also produce an unpleasant smell.
If your head gasket is experiencing problems you may need to have the cylinder head replaced as the head gasket will likely be distorted due to the heat.
We would strongly recommend getting the problem fixed as soon as possible if you notice blue smoke coming from your exhaust. If your car is leaking oil, there will come a time when there isn't enough to properly lubricate your engine. This can lead to expensive damage!
To find out exactly why there is blue smoke coming from your exhaust and to get the problem fixed, book an exhaust repair with a local garage.
Why is There White Smoke Coming From My Exhaust When Accelerating?
If you notice thin white smoke at the start of a journey or when the exhaust is cold, you shouldn't worry too much. The smoke should stop once you get the engine and exhaust up to proper working temperature.
However, as a word of warning, if you complete a lot of short journeys and see white smoke frequently, it could become more of a problem. White smoke is steam (evaporated water vapour).
If the exhaust doesn't get up to its proper working temperature, it won't remove all the condensation this causes. This can rust and corrode your exhaust. If this gets too bad, it can fail the MOT emissions test! Try and avoid using your car for short journeys if you can walk or cycle instead.
An internal coolant leak could be to blame if you can smell something sweet coming from the exhaust - this can be caused by a damaged cylinder head or engine block.
A failing coolant system can cause your engine to overheat and lead to head gasket failure - in which case you should stop driving immediately and call a mechanic.
A faulty fuel injector may also be sending too much fuel into the combustion chamber, whilst diesel cars may also suffer from issues with injector pump timing.
If the white smoke increases or won't go away or your engine temperature begins to rise, stop the car as soon as possible. Then, book an appointment at a local garage and get it towed there for an inspection and repair.
Why is There Black Smoke Coming From My Exhaust When Accelerating?
If you drive a diesel car, you shouldn't always worry about seeing black smoke while accelerating. If you only notice it when the engine is first switched on or under hard acceleration, it could just be uncombusted diesel escaping from your exhaust. It should go away once you get your engine up to proper working temperature or stop accelerating.
However, if the black smoke persists, is more frequent or is constantly pouring from your diesel car, it's a much more serious problem. The most likely suspect? Worn fuel injectors.
Your car knows how much fuel it is supposed to inject. It releases the right amount of fuel through the fuel injector's nozzle and keeps your car running smoothly.
The only problem is that the nozzle can enlarge over time. So, while your car knows exactly how much fuel it's supposed to inject, it's based directly on the size of the nozzle - and it can't tell how much it has enlarged.
Long story short, if the nozzle is too wide, too much fuel gets injected into the engine. This leads to incomplete combustion and large clouds of black smoke.
Black smoke can affect both petrol and diesel cars, and could suggest that the fuel has been contaminated. Diesel cars may produce black smoke if there is a build-up of soot in the diesel particulate filter (DPF), whilst petrol cars can suffer from a clogged air filter. Damaged turbochargers may also lead to the production of black smoke.
If you notice black smoke coming from the exhaust of a petrol car, there could be a serious fault or a worn engine. Stop driving immediately and book an appointment at a local garage for a repair. Make sure you get a recovery truck to tow your vehicle there.
Why is There Grey Smoke Coming From My Exhaust When Accelerating?
There are four main problems that cause your exhaust to produce grey smoke when accelerating:
- A faulty turbocharger
- Too much oil in the system
- A faulty PCV (Positive Crankcase Ventilation) Valve
- A transmission fluid leak (Automatic cars only)
If you notice grey exhaust smoke, this is most likely oil leaking into the combustion chamber. This can be attributed to a faulty valve stem seal, which you will need a mechanic to fix for you - a worn out positive crankcase ventilation valve (PCV) can also be mended by a mechanic. Damaged piston rings or a worn out turbocharger also need to be looked at - stop driving if it is the latter, as you will only cause further damage to the engine.
If too much oil is your problem, it may just burn itself and the grey smoke should disappear. Unfortunately, the same can't be said of the other issues on this list. When you notice grey smoke coming out of your exhaust for an extended period of time, avoid driving and book an appointment at a local garage.
All of these issues require a professional inspection to diagnose. What's more, they could end up being very costly repairs even without making the damage worse - so don't risk it!
Why Does My Exhaust Rattle When Accelerating?
An exhaust rattle usually means that the exhaust system is loose or misaligned. There are many reasons for this, including:
- Rusted or missing brackets
- External damage from a collision
- A leaking exhaust.
If you hear your exhaust rattling, you should treat it as a serious fault. Don't turn up your music to drown it out and hope for the best. A loose exhaust is an inefficient exhaust - and that could mean that Carbon Monoxide is filtering into your cabin! This silent killer is incredibly deadly and should be dealt with immediately.
If you hear an exhaust rattle, open the windows to keep your car well-ventilated and try to avoid sitting in your vehicle while it idles. If you start to feel dizzy or light-headed, stop driving immediately and get out of the car. This is a sure-fire sign that you are about to be overcome by Carbon Monoxide.
Other components within your exhaust system - such as broken pipes, rusty mufflers, failing catalytic converters, and blown exhaust gaskets - can all be the cause of the rattling noise.
A broken heat shield can produce a rattling sound whilst accelerating, as more strain is placed on the engine. You may notice decreased performance, a burning smell, and your engine may even overheat. You should always stop driving if you suspect that your engine is overheating.
Engine mounts keep the engine in place - if they come loose, so will the engine. The rattling noise whilst accelerating can come from the two parts touching, which could lead to drivetrain failure. You may notice that your wheels are out of alignment, the car is leaking oil, or there is engine vibration - you should have a mechanic take a look if this is the case.
Worn or stuck valve trains that result in premature ignition in the combustion chambers can also produce this rattle. Whilst you may just need an oil change, it is still worth having your car checked out by a garage.
To fix a rattling exhaust, you must book an appointment at a local garage. Get your car towed by your breakdown provider rather than driving it there to keep yourself safe.
What Causes a Noisy Car Exhaust?
Several problems can cause a noisy car exhaust. On top of that, each noise is a sign of a different problem. Here's what your noisy exhaust could mean:
Chugging Noise = Blockage in the system.
Roaring Noise = Faulty silencer or muffler.
Hissing Noise = Crack in the exhaust manifold, exhaust pipe or head gasket. Missing mounting or sealing bolts, missing sealing clamp.
Rattling Noise = Misaligned exhaust or a loose part.
Loud Metallic Vibration = Something touching the exhaust pipe or clamp or a missing support bracket or mounting.
Any exhaust noise is bad news - especially a hissing noise! If you hear any of the above or another noise that you're not happy with, book an inspection at a garage near you.
Avoid driving the car as much as possible and try and get it towed to the garage rather than driving it yourself.
Why Can I Smell Exhaust Fumes?
If you can smell exhaust fumes, it is very likely that your exhaust is leaking. Exhaust gases that usually escape out the back of your car are escaping somewhere else and filtering into the cabin.
Before you start to panic, make sure that the exhaust smell is definitely from your car. Sometimes, other drivers' exhaust gases filter into the cabin through the ventilation system. If that's definitely not the case, pull over immediately. We also don't recommend driving your car to a local garage to get the problem fixed. You should contact your recovery provider instead and get it towed. You could suffer from Carbon Monoxide Poisoning, which is a very unpleasant experience and can put your life in danger.
Other reasons that you're smelling exhaust fumes include:
- A broken catalytic converter (smells like rotten eggs)
- Broken heater core (burning antifreeze smell)
- Burning oil (smouldering smell in cabin)
If you're smelling any of the above, you need to book an inspection at a garage near you. Once the mechanic has found the issue, they will be able to provide a suitable repair.
How Do I Find an Exhaust Leak?
An easy way to find an exhaust leak is to identify when you smell the exhaust fumes.
Can you smell them all the time? Then the leak is somewhere near the front of your system. This is usually caused by physical damage or a problem with the exhaust manifold gasket.
Do you only smell fumes while idling? Then the problem is likely at the back of the system.
Pinpointing the leak can help the mechanic who fixes your car complete the job quicker.
If you want to find the exact cause of your exhaust leak, you can complete a full visual inspection. However, DO NOT TOUCH any part of your exhaust at any time as it will be very hot.
While the engine is running, lift the bonnet. Find the exhaust manifold and check the condition. You can use your vehicle handbook to help with this. You may see that the manifold is rusty or has an obvious hole (which is a pretty simple diagnosis).
If that doesn't seem to be the problem, listen for any weird noises along the length of your car while the engine is idling. The louder the noise, the closer to the engine it is.
You might also want someone to rev the engine for you while you listen. This will help you identify any changes in the exhaust noise.
What Should I Do If My Exhaust Has Fallen Off?
The muffler is the only part of the exhaust system that can fall off (see below).
You're probably going to notice if this happens. There may be a loud shearing noise, a clunking sound as it hits the road or you may see it on the road in the rearview mirror. Stop your car as soon as you notice that your muffler has fallen off.
If it has fallen into the road, try and move it - but be careful, as it will be very hot for a few minutes. If your muffler falls off on the motorway, call the police and make sure you keep yourself safe while waiting for help.
Once you have retrieved the muffler, you should get a professional opinion about whether it is still usable. It doesn't matter whether it is reusable or not, but you do need to get a muffler reattached as soon as possible. Failing to do so can cause an MOT failure in the emissions test.
Always seek a professional opinion before deciding if your muffler is safe to reattach or not. The easiest way to do that is by booking an appointment at a garage near you.
How Do I Solve Any Of These Common Exhaust Problems?
Throughout this article, we've mentioned that you need to get your car to a local garage as soon as possible to get your exhaust problems fixed. While that may seem obvious, how you find a great garage near you and get the best deal on your exhaust repair might be a little less clear.
Well, the answer to that exhaust related problem is BookMyGarage.
Our online comparison site contains thousands of fully-qualified independent, franchised and fast-fit garages that can complete a high-quality exhaust repair or replacement.
Enter your vehicle reg and postcode to compare their labour prices, availability, distance and reviews and ratings, then select a suitable date and time to book a FREE visual inspection with the one that suits you best. Once you agree to the work, you deal with the garage directly and never pay a penny until after they've completed the job.
Most importantly, you get to compare everything like-for-like. If you're looking for the cheapest exhaust repair in your area, BookMyGarage is the place to find it.
Join over 5 million drivers who have compared and saved on MOT, servicing and repair costs through BookMyGarage today. Get a quote for your exhaust repair or replacement online now.