How To Diagnose Strange Smells And Odours From Your Car

One of the things about owning a car, regardless of its age, is that you will come to notice all sorts of weird and wonderful smells and odours coming from various parts of it.


Whether it be a smell coming through your air vents, from a certain part of the engine or from underneath the car, some smells and odours might be unfamiliar to you, and you may become concerned about whether it’s something that could lead to a big (and expensive) problem that you will have to sort out.



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Let’s face it; the only things you should smell inside your car are air fresheners or the scent of your takeaway food in a bag that your passenger is holding onto for you!


So if you have started to notice a smell that is unfamiliar to you and is definitely coming from your car, here is how you can diagnose what the cause of it might be. Thanks to Motorline Direct for compiling this handy list!


Engine smells


Sometimes you might notice some smells originating from the engine bay that you can at times smell through your air vents:


  • Burning rubber – if you notice a smell of burning rubber under the bonnet, chances are one of your hoses may have become loose or partially collapsed onto a hot engine part such as the exhaust or the engine block itself;
  • Burning oil – you are highly likely to smell burning oil from older cars. This can be due to a number of things, such as a leaking sump plug, oil seals, or even an oil cap that hasn’t sealed properly. These odours can typically be smelled from the inside of a car after a long journey or when standing near the engine bay with the bonnet open;
  • ‘Sweet’ smells – do you happen to notice an aroma reminiscent to sweets? There is only thing that can cause such a smell from your engine, and that is from the coolant (or “antifreeze”). Causes can range from a slight hose leak by the expansion tank to something major like a failed cylinder head gasket;


Exterior smells


Although most smells are sourced from some part of the engine, there are occasions where you can smell something only from the outside of the vehicle.


For example, if you smell a strong odour like something burning, but the smell does not come from the engine bay, it is highly likely to be braking related. Driving along with the handbrake up is the most common cause, alternatively you may have faulty brake pads or shoes on one of your wheels (this is sometimes known as binding brakes).


Fuel smells can sometimes be noticed when you’re standing outside of your car. If you notice a slight hint of petrol in the air when you start your engine this is normal, but strong smells indicate you have a fuel leak somewhere – in such cases you should get your car to a garage immediately!


Another common source of strange smells is from the exhaust:


  • Oil smells – this usually indicates that your engine is burning oil, and the most common culprits are either blocked hydraulic lifters or lash adjusters (top end), failing valve stem oil seals (top end) or worn piston rings (bottom end);
  • Egg smells – the catalytic converter is the cause of such smells, and this may indicate that it or some other parts of your car’s emissions system could be failing.


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