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Firstly, this question is written by someone with very little knowledge of cars. So, please bear with me.

Some weeks ago, I was driving to work and smelled this horrible, thick, burning odour. Given that I hadn't smelled anything like this before when driving, I pulled over and opened the bonnet. (I don't really know why - I guess I was expecting to see fire.) But it looked OK. Nothing visibly wrong and I carried on to work; the burning smell died down after 2-3 minutes.

The smell must have happened again two or three times following this. I finally asked my friend in work who suggested it could be the clutch or a build up of something - he suggested some italian tuning. Since then, the thick smell went away.

However every so often I will smell this much lighter burning smell and unless I am totally mistaken, I think it's coming from the bonnet. Anyway, I took it to the garage today and they couldn't find anything at all. Clutch is fine and they couldn't spot anything wrong.

Can anybody offer some things to look out for or try so I can get to the bottom of this.

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It sounds as if you have driven over a plastic bag and it got stuck to your vehicles hot exhaust. And now its slowly melting it away.

You could visually inspect the exhaust to confirm. It should look like a black blob or the ruminants of a plastic bag.

Make sure you don't touch it after the vehicle has been driven. The exhaust is know to get rather hot (extremely hot) and will leave quite the mark.

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Thanks for this suggestion. I will look in the morning with some light! – Federer May 10 '14 at 21:03

Engine oil leaks (or any other oil for that matter) can cause a smell if drips onto the exhaust. It wouldn't have to be a large oil leak to cause a noticeable smell, just even the occasional drip. I have also seen an engine that would have a small leak overnight and would smell first thing in the morning when it was started until the oil burnt off. Another example which is common is a small oil leak externally on a turbo (may not be applicable in your case) where the oil is likely to get very hot and smell.

It is difficult to see an oil leak without being under the car, but check all fluid levels anyway.

I have also recently seen a Subaru with the inner C.V joint boot on a front driveshaft had torn throwing grease directly onto the Exhaust CAT which caused a bad smell.

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Found a bird once stuck on a radiator and also a rodent of some sort stuck around the heater core. Both owners complained of a burning smell that went away after removal of burnt corpses.

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Christ, I really hope this isn't it! – Federer May 10 '14 at 21:02

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