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 servicenWorn-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?

White smoke coming from your exhaust is either your engine warming up or a sign of a coolant leak. As you can probably guess, one is much worse than the other. 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 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. 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.nnRoaring 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).nnnnnYou'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.

9 FAQs About Common Exhaust Problems (Answered)

To keep your exhaust in good condition, you need to be able to spot when something is wrong.

Any unusual exhaust noises, smoke or leaks can all signal that your vehicle has an exhaust problem.

Read on and find out if you have an exhaust problem, why your exhaust may be smoking and why it may be making noise.

Page Contents

Signs You Have an Exhaust Problem
Why is My Car's Exhaust Smoking?
Why is My Exhaust Noisy?
Where is the Noise Coming From?
What is a Car Exhaust?
What Does a Car Exhaust Do?
How Much is a New Exhaust?
Why Do MOT Tests Include an Exhaust Emissions Test?
How to Prevent Exhaust System Problems

Signs You Have an Exhaust Problem

Your vehicle could be experiencing an exhaust problem if you notice any of the following warning signs:

An illuminated check engine light
Poor vehicle performance
Steering wheel vibrations
Visible discolouration of the exhaust tips
Audible exhaust rattle
A rumbling or hissing sound
A broken catalytic converter
Increased engine noise
Smelly exhaust
Decreased fuel economy

A mechanic will be able to advise you as to whether you require an exhaust repair or replacement.

Why is My Car's Exhaust Smoking?

Your car exhaust could be smoking for several reasons, including:

A leaking head gasket
A faulty coolant system
Burnt electrical wires
Worn out pistons
Faulty fuel valves

If you regularly maintain and service your vehicle, then any visible exhaust emissions will likely not be an issue – though you should still check this.

When diagnosing a smokey car exhaust, take note of when and where the smoke appears.

If the smoke only appears when the car is stationary, there could be a different issue to smoke that appears when accelerating, for example.

Fire Under the Bonnet

If you identify that the smoke is being caused by a fire under your car bonnet, you need to turn off the engine immediately.

Pull the bonnet release lever – do not attempt to prop it open.

Everyone should exit the vehicle and stand well back.

You should call the emergency services.

Car Smoking but Not Overheating

If your car is smoking but not overheating, then this could be the result of any of the following issues:

Leaking coolant
Oil leaks
Faulty wiring

White Smoke

If you notice white smoke coming from your exhaust, this is likely steam caused by condensation in the exhaust pipe.

Alternatively, your vehicle could be leaking coolant or experiencing head gasket failure.

White smoke coming from your car exhaust can be caused by a cracked engine block or damaged coolant or radiator hoses.

Black Smoke

If you drive a petrol car and see black smoke, then it is likely that too much fuel is being burned off.

Your vehicle may also be suffering from air filter or fuel injector problems.

If your drive a diesel car, then a blocked diesel particulate filter (DPF) could be to blame.

Provided the filter has not become excessively blocked, you should take your car for a long drive on the motorway to try and trigger the regeneration process so that the filter can clean itself.

Blue Smoke

Dark grey or blue exhaust smoke signals that your engine is burning oil.

This can leak into the combustion chamber where it is burned with fuel.

Your engine may misfire when you turn the keys in the ignition or the vehicle may shake more when idle if this is the case.

These leaks can be caused by any of the following components being worn out or damaged:

Head gasket
Inlet manifold
Engine oil seals
PCV seals
Valve stem seals
Pistons
Piston rings

You should have your vehicle inspected by a professional mechanic if you notice blue exhaust smoke.

Grey Smoke

Thick grey exhaust smoke usually means that your vehicle is burning oil.

When this leaks into the combustion chamber, this can reduce fuel economy and cause damage to the catalytic converter.

A faulty valve stem seal or piston ring could be to blame.

Blueish grey exhaust smoke when accelerating will need to be addressed by a professional mechanic, as the piston rings could be damaged.

Why is My Exhaust Noisy?

Different sounds can point towards different exhaust issues.

Hissing Noises

Hissing sounds are often a sign of an exhaust leak, signalling there could be a crack in the exhaust pipe, exhaust manifold or a leaking gasket.

Roaring Noises

A roaring noise can indicate that there is a car sound silencer problem.

Chugging Noises

There could be a blockage in the exhaust system if you hear a chugging noise.

Rattling Noises

An exhaust rattle usually indicates that the system has come loose or suffered a misalignment.

Where is the Noise Coming From?

In addition to determining the type of noise you’re hearing, working out where the sound is coming from can help you pinpoint why your exhaust is noisy.

Front of Car

If you notice loud exhaust sounds coming from the front of your car, then you may have a bad gasket, a loose flexible pipe connection or a cracked exhaust manifold.

Centre of Car

If your hear exhaust noises from under the centre of the car, then there could be a loose connection or a hole in your exhaust.

Alternatively, there could be a problem with the catalytic converter – which will likely be expensive to repair.

Rear of Car

Noises from the rear of the vehicle are usually related to the muffler or caused by a hole in an exhaust system pipe.

What is a Car Exhaust?

Your car’s exhaust system manages the expulsion of gases produced during the engine combustion process.

What Does a Car Exhaust Do?

The exhaust in a car serves 4 main purposes:

Noise control
Improving engine performance
Improving fuel consumption
Directing exhaust fumes away from passengers

All exhausts produce gases as emissions, and the exhaust emissions system channels these noxious fumes away.

Exhaust gases are collected from the cylinder head in the engine by the exhaust manifold, which diverts the gases from the engine cylinders and releases them through the front pipe.

The exhaust gases go through the catalytic converter, which removes the harmful elements and converts them into inert gases.

These gases can then pass through a silencer or a muffler before exiting via the tailpipe.

How Much is a New Exhaust?

Whilst this will vary depending on your vehicle and where you’re based in the UK, an exhaust replacement can cost as much as £2,000.

An exhaust repair can cost up to £600.

Parts and labour costs will also have an impact on the price.

If you notice that your engine is becoming noisier, the exhaust is corroded or you are having to fill up more often, then you may need a new exhaust.

Why Do MOT Tests Include an Exhaust Emissions Test?

The emissions test is part of MOT testing to ensure vehicles in the UK comply with government standards.

The exhaust emissions test ensures that the pollutants emitted from your vehicle’s exhaust are within the legal limits.

This test is mandatory for all diesel, petrol and gas-powered vehicles that have 4 or more wheels.

Depending on when your vehicle was first used, the test may be visual or it may be a metered smoke test.

If your vehicle produces higher emissions than expected, you could fail the MOT test.

Please note that your vehicle could be tested during a roadside check.

To give your vehicle the best chance of passing, you should book regular car services and deal with exhaust problems quickly.

How to Prevent Exhaust System Problems

To reduce the likelihood of exhaust system issues occurring, you should have your exhaust system inspected every year.

Regular car servicing and vehicle maintenance can help to prevent exhaust system damage.

A Guide to Common Car Exhaust Problems