Joseph Law

Bumper Content Writer

Smoke from your car's exhaust can be a worrying thing to see, regardless of the colour, as it’s usually an indication of something wrong. 

The one upside of seeing said smoke, however, is that it can be very useful in diagnosing the issue, for differing problems cause different colours. 

In this blog, we’ll explain the potential causes for any colour exhaust smoke you’re likely to see. 

Even if a car is running perfectly, you may still see some light white smoke or steam from the exhaust, particularly on cold days, for the first few miles of driving. 

Older diesel-engined vehicles may also emit a small puff of black smoke upon hard acceleration, but not constantly. 

Other than those two cases, an engine that is running well should not produce visible smoke. If your car is producing smoke, pay close attention to the colour of it, as this can often tell you a lot about the nature of the underlying problem. 

What Coloured Smoke Means From an Engine 

, keep an eye out for what colour it is, this can either be done by having a friend rev the engine slightly whilst stationary, or checking behind you whilst driving. 

What causes white smoke from your exhaust? 

A little white smoke at the very start of a journey is normal, but thick consistent clouds of white smoke mean your engine is burning coolant, which tends to indicate a head gasket failure or worse. 

For more information on white smoke, we have an entire blog article about the causes and symptoms. 

. There are a few different ways this can happen, as there are multiple sealing points stopping oil from entering the engine. Likely causes include: 

In cars with turbocharged engines, this is a very common cause of oil being burnt, 

 use oil to lubricate the spinning shaft, they have seals to prevent this oil from entering the air stream into the engine. 

This is a valve that redirects exhaust gases that get past the pistons and into the crankcase (bottom half of the engine), when the system gets blocked oil can be pushed through instead of gas, and be burnt in the cylinders 

Piston rings seal the piston to the cylinder wall when worn from very high mileage and/or poor oil servicing, they then allow oil into the combustion chamber 

Another sealing component, valve guides hold the valves that allow air into the engine. When worn they allow oil into the combustion chamber.

What causes black smoke from a petrol engine? 

Large amounts of black smoke tend to indicate the fuel-air ratio is too rich - that is there is too much fuel for the amount of air entering the cylinders. This can be from either too much fuel, or not enough air. 

Too much fuel entering can be caused by the 

 not properly metering the fuel when spraying into the engine, allowing excess fuel to go unburnt and appear as black smoke.

The main job of the turbo is to increase the amount of air entering the cylinders, a fault with the turbo e.g. worn bearings or a stuck actuator, will have a dramatic effect on the amount of air entering the combustion chambers, causing air/fuel mixture that is far too rich. 

What causes black smoke from a Diesel engine? 

Diesel engines are different in their operation to petrol engines, whilst all of the issues listed above can be present in a 

, there are other causes only a diesel car will experience. 

The diesel particulate filter is a diesel-specific emissions device used to reduce the amount of soot present in an engine's exhaust gases. Soot is created as part of the diesel engine cycle, but in cars fitted with a DPF, this is trapped and converted to ash. 

 can cause visible soot to be emitted, the removal of the DPF entirely is also another cause for soot to exit the exhaust. This will usually occur on heavy acceleration. 

Every diesel car from 2009 will have a DPF - and some made before then too - check out our guide on 

What causes grey smoke from your exhaust? 

Grey smoke can be caused by a few different things, if a small amount of engine oil is being burnt, this may not present as thick black smoke but a lighter colour that looks grey in daylight. 

 use a modulator system that is powered by negative pressure. As the engine's intake manifold experiences negative pressure in most situations, gearbox modulators are sometimes connected to the intake manifold. 

If a problem occurs with the modulator, the vacuum in the intake manifold can suck transmission fluid into the intake, causing it to be ignited along with the fuel. This isn’t a very common problem and will only happen if the following conditions are met: 

Can I drive my car if the exhaust is smoking? 

If the smoke dissipates quickly after the engine has warmed up, it's probably just water vapour and the car will be okay to drive. However, if the smoke is constant, regardless of the colour, you should not drive any further than necessary, ideally to a garage or repair centre. 

Not only could the smoke-causing issue damage your engine, but it could also get you in trouble with the police if you’re obstructing the view of other drivers. 

If you can smell exhaust or fuel fumes inside the car, refrain from driving as soon as possible, finishing the journey with the windows open. Being able to smell exhaust fumes inside the car is an indication there is a significant exhaust leak. 

If you can smell exhaust or fuel fumes inside your car, take it to a mechanic or garage as soon as possible, continuing to drive could cause coughing, breathing difficulties and other long-term effects. 

, you can split the cost of repairs and services into monthly payments at no additional cost. Choose from 1000s of reliable garages and dealerships across the country.

 has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.

Why Is Smoke Coming Out of My Exhaust & What The Different Colours Mean 

¿Por qué sale humo de distintos colores del tubo de escape?

Cars are complex things, and because of this, they have many different ways of telling us as drivers, when something is going wrong. Often this appears in an easy-to-see 

 or a written warning, but sometimes it’s more subtle. 

The colour of the smoke from your exhaust can be a real indicator of the health of the engine, if you have white smoke coming from your exhaust, be sure to read on. 

In an ideal world, and with a car that’s running well, you should never expect to see much from the 

Light-coloured white smoke/steam is normal especially when starting the engine on a cold day, the moisture from the air condenses in the exhaust as it heats up. The force of the exhaust gases then expels this as steam from the tailpipe. 

What Causes White Smoke from the Exhaust 

Large amounts of thick white smoke from the exhaust are usually caused by the engine burning water in the cylinders, producing steam that looks just like smoke. This can be caused by a few different issues, one of which is a 

Unfortunately, a blown head gasket is the best-case scenario for an engine producing white smoke; other causes can be from a cracked or warped engine block or a cracked cylinder head. 

White smoke coming from the exhaust in cold weather 

A small amount of white smoke when just starting the car, that dissipates into the air quickly, is usually not a sign of anything serious; it’s actually just water vapour and is usually more noticeable on colder days. 

Minimal white ‘smoke’ when the engine is cold is caused by a similar principle to us being able to see our breath on a cold winter's day; the cold, humid air condenses inside the exhaust and is then turned into steam by the extremely hot exhaust gases. 

Once the exhaust has warmed up fully, the smoke will stop.

How to Check if White Smoke is Caused by a Blown Head Gasket 

If your car is producing white smoke, it may be caused by a blown head gasket. There are a few key points to check to help diagnose the problem 

Does the smoke continue after a few minutes of driving?

If so, then there’s a good chance the engine is burning coolant through either the head gasket or a cracked cylinder head and/or block. 

Coolant should stay at a constant level, with only very minimal losses over many thousands of miles. If you’re having to top up your 

 regularly and have constant white smoke, it’s likely your head gasket has blown. 

If you can see bubbles rising inside your expansion tank, along with the two previous symptoms, there is a strong chance the pressure inside the cylinder is pressurising the coolant system through a break in the head gasket. 

An inexpensive test you can do at home is a block leak test, which uses a simple device to check if exhaust gases are escaping through the coolant system, a surefire sign that the head gasket is blown. 

The kits are around £20 and involve adding some of the included liquid into the plastic device, then this is held over the coolant expansion tank with the engine running. Be sure to follow the instructions on the product, and never open the coolant tank when the engine is already hot. 

For more information on what a blown head gasket means for your car, read our guide 

How to Fix White Smoke Coming From Your Exhaust 

As we’ve discussed, if the white smoke or steam is thick and continues even after the engine is warm, it is likely to be a blown head gasket. You can follow the steps above to check for this. 

In the event of a blown head gasket, the engine will need substantial work at a garage. Thankfully, many engines can be stripped and rebuilt without the need for expensive machining work, as long as the engine hasn’t overheated severely. 

If it has overheated, though, the block and head may have been warped - resurfacing of one or both parts will then be needed, adding more time and expense to the job. 

Unfortunately, there are no real solutions to a cracked engine block that doesn't require a new engine. The cheapest way to achieve this is often with a second-hand engine from a breaker’s yard or dismantler. 

Is White Smoke from the Exhaust in Winter Normal? 

White smoke isn't always a serious issue; if the smoke/steam dissipates easily and stops after the engine is warm, it is caused purely by condensation in the exhaust. 

This is much more prominent in winter, due to the water vapour being easier to spot - just like being able to see your breath.

To conclude, white smoke from your exhaust is often seen on cold days and is generally harmless, but it’s good to be aware of what to look out for if it persists. For more information on car maintenance and car repair tips, check our blog.

White Smoke From Your Exhaust: Causes, Diagnosis & How to Fix It

Why is white smoke coming out of my exhaust?

¿Qué significa el humo blanco del tubo de escape?

Warum kommt weißer Rauch aus dem Auspuff meines Autos?

It can be easy to miss, but water leaking into your car can cause serious issues if left to worsen. Thankfully there are some telltale signs to identify when you have rainwater leaking into your car interior, and some common causes that can help identify the cause. 

If you notice any of these signs, it’s wise to investigate fully to find the cause of the leak, before it causes irreparable or expensive damage. 

An unmistakable sign that water is entering your car is if the floor mats are sodden, which is likely to be especially noticeable after heavy rain or a period of not driving the vehicle. 

It's likely if the floor mats are wet, then the carpet too will be soaked through, the extent of which can help identify where the leak has originated from. 

When water leaks in through seals, it is likely to also bring some road grime, dust and dirt. If this water soaks into your upholstery, be that the seats, carpet or headliner, it is likely to leave a discolouration. 

Usually an off-white or light brown colour, discoloured fabric is an easy way to identify where the water is entering, marks on the headliner are likely to be from a leaky sunroof, for example. 

3. Window misting or screen freezing on the inside 

Excess moisture inside a vehicle will present itself in a couple of ways, if it's particularly cold outside the vapour may condense on the inside of the 

. Alternatively, it can simply fog up the windows, requiring wiping or airing to remove. 

If your windows constantly fog up, check for other signs of leaking. Usually, the windows will fog nearer the source first, for instance, a broken boot seal will cause the rear window to fog most.

One of the most common causes of a smelly car interior is an old water leak that has not been addressed, or at least the upholstery is not sufficiently dried out. 

To remedy a mouldy-smelling interior, with no obvious leak, thoroughly clean the carpets and floor mats. Once clean and dried, monitor closely the carpets around the problem areas for dampness, especially after rain. 

If you’re experiencing strange electrical faults with no apparent cause, ruling out a water leak is a good step. Problems usually occur in cars that have the 

 located in or around footwells and by door frames. 

This is one of the most unfortunate ways to find out you have a water leak, as it may be too late to save the damaged components if the faults are caused by water damage. Check with an auto electrician if the faults persist. 

A noise similar to water moving around in a half-full water bottle is often caused by water getting into your doors. 

Water entering the door frames is not actually uncommon, the seals on the outside are not designed to prevent all water ingress. Instead, the doors have drain holes to allow the water to simply drain away. 

If these drain holes become clogged, the water can build up, potentially leaking into the car, causing problems with electric windows and speakers, or causing the door itself to rust. 

Water leaks can be difficult to trace, but there are only a certain amount of entry points on most cars. 

Whilst there aren’t likely to be any specialist damp/leak experts for cars, any general mechanic should be able to investigate water leaks in your car. 

If possible, we’d suggest a garage that specialises in your make of car, as they are more likely to have come across the common causes on that specific model before. 

Split the cost of repairs into interest-free monthly repayments with 

The cost to fix water leaks can be anywhere from £50 to £2,000+, depending on the level of damage caused by the water before it is fixed. 

Some water leaks can be fixed simply by replacing a broken seal or rubber, some may even still be present but have simply become dislodged from their intended position. Both situations would be reasonably cheap to fix. 

If there has been rainwater leaking into the car for a while, costs could quickly rise if electrical systems have been damaged, or upholstery needs to be professionally cleaned or replaced. 

If you have a water leak and are wondering whether to bother getting it sorted, we would recommend doing so as soon as possible, purely to avoid hefty bills down the road. Water damage can be significant. 

 controls every electrical system in a car, and the module is sometimes mounted near potential water ingress points. 

The cost of repairing water damage to your car's ECU could easily run into the thousands, as a replacement often involves also replacing ignition key modules, immobiliser modules, door locks and more.

If water leaks are left unabated, mould is likely to develop, this combined with staining, carpets and seats can be damaged to the point of being uneconomical to repair. 

As they’re not a service item, replacement carpets and seats can be hard to come by, and take many hours to replace. 

, and whereas modern cars are protected from this by design (as well as their paint), water-logged carpets and upholstery can cause untimely corrosion to areas such as floor pans, bulkheads and roof panels. 

We’ve explained why it's critical to fix a water leak, and how to spot one, but how do you fix a water leak in your car? The answer generally depends on where the leak is from. 

Once located, assess the area from where the water is leaking, if a seal is obviously damaged or not properly secured, try to reattach or affix this. When investigating a leak, check for any loose bolts, screws or trim panels, as these could be preventing a seal where required. 

If the leak is not easily apparent, or you need to remove panels or components for better access, we’d advise seeking professional advice first. 

Whilst a short-term solution may not be perfect, it could help prevent further damage, as long as it doesn't become an insufficient long-term fix. 

Plastic bags or sheeting can be used to stop water ingress, or if the area of the leak is not known exactly, a car cover could be used to shield the affected area during a shower. Half covers are also available that just cover the roof and windows. 

We would not suggest using silicone sealant or glue as these can sometimes make the problem more difficult to fix permanently later on. 

, you can split the cost of car repairs at 4000+ expert repairers across the UK. Apply online before your visit to the garage in just a few clicks. 

Water Leaking Into Your Car When It Rains? Causes & Fixes

¿Agua filtrándose en tu coche cuando llueve? Causas y soluciones

Bei Regen dringt Wasser in Ihr Auto ein – Ursachen und Abhilfen

Rust has always been a problem for cars in the UK, as it's caused by wet winters and salted roads. 

The longer the rust is left, the larger the bill will be. So, if your car shows signs of rust, it's best to get it sorted as soon as possible. 

Today, we're here to explain rust repair costs while answering some common queries about this problem. Read on to find out how much you can expect to pay and how to find a garage near you.

The average rust repair costs around £360 for UK drivers.

However, costs can be anywhere from £200 for a patch rust repair, to £3,000+ for multiple panel replacement. The exact cost depends on the area, type of car, and extent of the rust. 

We’ve listed some common rust areas, their causes, and costs below. 

Split the cost of car repairs and service with Bumper 

. Choose from 1000s of dependable repairers. 

With cars having different shapes and designs, rust doesn’t always appear in the same place. Here are some five main areas you might find rust and how to spot them. 

Most areas most prone to rust are underneath the car, but the wheel arches are subject to more road dirt and grime than anywhere else. Wheel arches are often made up of an outer skin and an inner structural panel. 

Wheel arches catch any dirt, water, and road salt thrown up by the wheels. Rust will appear even faster if the area has a coating of mud, as this holds moisture against the steel. 

We also mentioned how wheel arches are made; this sandwich of metal sheets is the perfect place for any moisture to pool; wheel arches often rust from the inside out. 

How much does wheel arch rust cost to repair? 

Rear wheel arches are pricier as they're integral to the car's bodyshell, while front wheel arches often need only a wing panel replacement, costing around £500. The high expense is due to the wheel arch being part of the car's main body, requiring specialist welding, bodywork, and painting for a like-new repair.

Another common place for cars to show rust is on the sills. This is the section of the floor between the front and rear wheels that makes up the bottom section of the door frame. 

Road grime and water from the wheels hit the sills, but that's not all. Cars have drainage channels that direct rainwater through gaps between doors and into the sills.

If these drainage holes get blocked, water accumulates and causes internal rust. Regular maintenance and clearing of these holes can prevent rusting.

 for a rust repair. Since the sills are a structural component, they need to be repaired properly to pass an MOT.

Most cars have inner and outer sills. Severe rust on the outer sill likely means the inner sill will also need replacing with a welded new panel.

A common theme is that trapped water causes most car rust issues, including on the boot floor and especially in the spare wheel well.

Rust in the boot is an easy and important check to do when 

Standing or trapped water from boot leaks are the most common cause of boot floor rust.

What is the cost of repairing boot floor rust?

This repair price is more reasonable, as the boot floor is not seen. However, the final cost is still affected by the extent of rust, your location, and the make of your car.

 in older cars and should be fixed quickly to prevent fumes from leaking into the cabin.

Rusty exhausts are common in older cars, leading to leaks and eventual detachment. The main causes are road salt/water and condensation.

While road salt exposure is unavoidable, condensation can be minimised by reducing short trips. 

Water condenses inside the cold exhaust pipe when parked, but long journeys allow hot gases to vaporise this water, preventing rust buildup from shorter trips.

How much does it cost to fix a rusty exhaust pipe?

 are made from plain steel and not stainless steel.

Thankfully, exhausts are bolted to the engine and held by rubber mounts, making them easy for a garage to replace.

 are subject to road water, dirt, and salt. Older or high-mileage cars can experience higher levels of rust in these areas. 

Though most wishbones, control arms, and springs are painted to prevent rust, suspension components often get hit by stones and debris. This damage, along with exposure to water and salt, makes them particularly prone to rust.

How much does suspension rust cost to fix? 

Most suspension rust repairs cost between

. Like exhausts, suspension components can be unbolted and cheaply replaced.

Rust occurs when iron, oxygen, and water mix together - a process called oxidation. 

Rust is a common issue for car bodies, suspension components, and any other car parts that contain iron ore. Water and salt accelerate this process, and cars in the UK are exposed to significant amounts of both.

Here are some common questions about rust and car rust repair costs. 

Depending on its location and severity, rust can seriously affect your vehicle's safety, particularly on suspension components, sills, and subframes.

Even minor rust on bodywork like wheel arches, roof, boot lid, doors, and front wings should not be overlooked. Addressing it promptly is a proactive step towards maintaining your vehicle's safety and longevity. 

Since rust is an ongoing issue, you should fix it promptly to reduce repair costs.

 if the rust is extensive and on a structural component (e.g. sill, subframe, or suspension). 

Similarly, rust on the bodywork within a specified distance of suspension mountings or seat belt anchorage points will also not pass an MOT. 

If your car has surface rust, you can touch up specific areas at home.

Use rust converter paints on clean, rust-free areas to turn rust into a solid material and prevent further rusting. 

Professional welding is required for rust on structural components or inside-out rust. After applying the converter paint, the area should be finished with colour-matched paint and a top coat.

Rust requires ongoing preventative maintenance, ideally before it starts.

Undersealing, a protective paint applied to the car's underside, helps prevent rust by shielding bare steel from water. A similar product can be injected into sills and wheel arches.

Car rust can start at any time. However, it’s more common in older cars that have experienced more bumps and time on the road. 

Other factors that can cause a car to rust earlier include damage, climate, and the quality of your paintwork. 

What are the different types of car rust?

. This occurs when water comes into contact with a contaminant or when paint damage exposes the metal.

The takeaway - Ask an expert about rust repair costs

So there you have it: rust can present a big problem for car owners if it isn’t fixed. 

If you’re unsure how bad your rust problem is, ask one of our experts. Otherwise, your car might experience more damage than it needs to. It’s always better to get a professional opinion if you’re unsure!

, you can split the cost of repairs into interest-free instalments. Apply online and choose from 1000s of garages and dealerships across the country. 

How Much Does Car Rust Repair Cost in the UK?

¿Cuánto cuesta reparar el óxido en un coche?

Was kostet die Reparatur von Rostschäden am Auto?

Winter in the UK can be a miserable time, especially for commuting or general travel, with frosted screens, frozen door handles and icy roads to contend with. One thing that can be even more frustrating, is having a windscreen that is frozen on the inside, find out how you can stop this happening! 

How to stop a windscreen from freezing on the inside 

What causes your windscreen to freeze on the inside? 

A frozen windscreen on the inside is caused by excess moisture inside the car, often introduced by wet clothes or a leak somewhere around the window/door seals. 

This moisture condenses on the glass and then is turned to ice when the outside air temperature drops overnight. 

If you can't find any leaks and don't keep wet jackets inside your car, check the climate controls are not set to recirculate, this can cause your breath to build up moisture inside during driving, which then freezes overnight.

How to remove ice from inside your windscreen 

To remove ice from inside the windscreen, it’s best to allow the car's heat to defrost the ice inside your car, as scraping can cause smudges and marks after it has defrosted. When doing this, use some cloth or towels to absorb the water, as allowing it to run down into your dashboard may well cause issues. 

If you don't have time to wait for the ice to defrost, using a small scraper is possible, but needs to be done with care to avoid covering the inside of your car in frost. 

If your windscreen has frozen on the inside, it’s important to fully clear this before driving, as it will affect your visibility. 

Don’t use any kind of aerosol or spray de-icer inside your car, the fumes given off will not be good for you. Also, the chemical solution could damage electrical components or upholstery inside your car. 

Is it normal to have ice inside your windscreen? 

Having a frozen windscreen is perfectly normal throughout the winter, but if you drive your car regularly it shouldn't freeze on the inside as often. 

It can be an indication that you have a leak, so if it’s happening repeatedly, and you have tried all the suggestions in this guide, it might be time to get some help from a mechanic, or if your car is within warranty, your dealership. 

If your car has niggling faults like we’ve talked about in this article, and none of the solutions have worked for you, it may be time to get some professional advice on the problem. Bumper allows you to split car repair costs into interest-free monthly payments. Find out more 

How To Stop Your Car Windscreen Freezing On The Inside

Tyre pressure monitoring is a great system to have, it allows you to be confident your tyres are at the correct pressure without needing to manually check each one. However, you may sometimes find the system mistakenly warning you of low tyre pressure, especially in the cold! 

This blog post will explain why this is, other causes of your tyre pressure light illuminating and what you can do to mitigate this. 

What is a Tyre Pressure Monitoring System and how does it work? 

As the name suggests, most tyre pressure monitoring systems or TPMS reads the air pressure in your tyres constantly and communicates this to a module in the car wirelessly. 

When the sensors detect a pressure that is lower than it should be, an alert will be shown to the driver in the form of a small light, a message on the dash screen, an audible tone or a combination of the three. 

Advice

Why Is Smoke Coming Out of My Exhaust & What The Different Colours Mean

White Smoke From Your Exhaust: Causes, Diagnosis & How to Fix It

Water Leaking Into Your Car When It Rains? Causes & Fixes

How Much Does Car Rust Repair Cost in the UK?

How To Stop Your Car Windscreen Freezing On The Inside

Why Does My Tyre Pressure Light Come On In The Cold?

Cheapest ULEZ-Compliant Cars

Car Won’t Start in Cold? Causes & Fixes