We've all been there - driving along and suddenly you get a whiff of something strange. Most of the time it can be blamed on the outside environment, from farmer's fields to factories, but what if it stays with you?

According to one car expert there are a number of unusual smells which mean something is up with your vehicle. Tim Alcock, Sales and Marketing Director at LeaseCar, says a strange smell can be one of the earliest and most critical indicators of a mechanical issue, potentially saving drivers from costly repairs or dangerous situations.

And failure to act quickly could leave you with a hefty bill. Tim explains: "A car's warning lights are important but your sense of smell can be an equally powerful diagnostic tool. Many mechanical problems produce a distinct odour long before they cause a breakdown.

"By learning to identify these smells, drivers can take a proactive approach to maintenance and ensure their vehicle remains safe and reliable." Tim has compiled a list of common and uncommon car odours, and what they could mean:

"This isn't the smell of a forgotten breakfast, it's the smell of a potential fire. The odour of burnt toast is an unmistakable sign of an electrical issue. It usually means that plastic insulation on a wire is melting or that a short circuit is causing a component to overheat. An electrical fire can spread with shocking speed and leave you stranded quickly. My advice is simple, pull over immediately, turn off the engine and disconnect the battery if you can do so safely. You may need to call roadside assistance for further diagnostic evaluation as this is not a smell risk driving home with."

"Not just foul smell, rotten eggs can indicate a serious vehicle problem. That pungent, sulphur-like smell is almost always a sign of a failing catalytic converter. This crucial emissions component is designed to turn toxic hydrogen sulfide into less harmful gases. When it fails, the hydrogen sulfide builds up and gives off that unmistakable stench. Occasionally rotten egg odour could be pointing to a fuel system issue or a leaking battery, but either way, the bottom line is that something is seriously wrong with your car if you begin to smell this. If you experience this, then the best course of action is to have your car inspected by a professional mechanic as soon as possible."

"Burnt carpet or hair is usually the smell of overheated brakes. It's most common after heavy, prolonged braking, such as on a steep downhill road. When brake pads get too hot, they lose their effectiveness, a dangerous condition known as brake fade. If you smell this during normal driving, it could mean a brake caliper is seized or a pad is sticking, causing constant friction. If you experience this smell, pull over swiftly and let your brakes cool down, as this is a sign that your braking system is compromised and needs attention."

"Maple syrup sounds delicious to smell but it is a dangerously deceptive scent. It's pleasant, yes, but it's a critical warning sign that you have a coolant leak. Antifreeze, which contains ethylene glycol, has a sweet scent that becomes more pronounced as it leaks onto a hot engine and vaporises. An unchecked coolant leak will inevitably lead to your engine overheating.To be blunt, an overheated engine is one of the quickest ways to cause catastrophic, irreparable damage. Check your car's coolant levels and look for coloured puddles under your car. Don't drive it until you've had this diagnosed."

"This strong odour is indicative of friction. It often signals a loose or slipping drive belt that's rubbing against a rotating engine component. This is a problem you want to catch early, because if a belt snaps, you could lose power steering, your alternator could stop charging the battery or your engine could overheat. It could also point to a problem with your brakes or even a loose tyre rubbing on a wheel arch. Whatever the cause, it's a clear signal that something is creating excessive heat and friction where it shouldn't be. As a snapped belt can cause a sudden loss of critical systems, you should pull over safely and have the issue inspected by a professional as soon as you notice any problem."

"This smell is unique to manual transmission vehicles and is the result of a slipping clutch. The friction material on the clutch plate can overheat from too much friction, literally burning like paper. This can happen from "riding the clutch" (resting your foot on the pedal), but more often it's a sign that the clutch is simply worn out and nearing the end of its life. While you might get a little more life out of it after first smelling burnt paper, if the clutch is on its last leg you should prepare yourself for it to fail completely and the potential risk of leaving you stranded. Pulling over safely and getting this inspected as early as possible can lead to avoiding a breakdown later down the line"

"This isn't just an unpleasant smell, it's a diagnostic curveball. A fishy or foul odour can sometimes be a sign of leaking gear oil or antifreeze dripping onto a hot component. Some of these fluids have a very specific, unpleasant smell when they're heated. On rare occasions, it can also point to an electrical short circuit. Whilst not as urgent as some other smells, this is a smell that needs to be investigated because it's pointing to a fluid leak in a critical system that you might not otherwise notice."

"This smoky, greasy smell is the calling card of an oil leak. Engine oil is escaping from a worn gasket or a cracked seal and dripping onto a hot part of the engine or exhaust. The danger here is twofold: it's a potential fire hazard and if the leak is significant, your engine could be running dangerously low on oil. A low oil level is a surefire way to cause serious internal engine damage. You should pull over safely and quickly to check your oil dipstick immediately if you find yourself in this situation."

"Exhaust fumes are the most critical smell of all. The odour of exhaust fumes inside the passenger cabin is an immediate safety hazard and not something you should ever take lightly. It points to a leak in your exhaust system, allowing toxic carbon monoxide gas (an invisible and odourless killer) to enter the vehicle. If you smell exhaust, you must immediately pull over, turn off the engine, open the window and exit the car to get fresh air. Do not continue driving. This scenario could lead to a life-threatening emergency."