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Smoke Signals. What does the smoke from my car exhaust mean?

Practical Motoring logo Practical Motoring 28/05/2018 Isaac Bober

© Provided by Practical Motoring Have you ever started your car and seen a big puff of smoke plume out from behind it? Here’s how to tell what the smoke from your car’s exhaust pipe means.

THE EXHAUST pipe is an emissions outlet for your vehicle, and while most people think that only diesel vehicles blow smoke, all vehicle types can and will blow smoke from the exhaust pipe(s). And the colour and duration of the smoke can tell you whether your car is healthy or very sick.

Like a doctor checking your vital signs, the colour of the smoke from your car’s exhaust pipe can tell a mechanic exactly what’s going on with your vehicle. And the smoke can vary in colour from the white vapour and occasionally some spluttery water you see when you start your car on a cold morning; this usually goes away once the engine has warmed up. Let’s get into this but, remember, this is just a guide, always have your vehicle checked by a fully trained mechanic.

White Smoke – Vapour

As mentioned, you’ll usually see wispy white smoke blowing from your exhaust on a cold morning while your engine warms up. You might even notice some spluttery water leaking from the exhaust pipe. This vapour disappears once your engine is warm; you can check your engine temperature via the gauge on your dashboard – it should sit around the half-way mark when your engine is warm. If your engine is still blowing white smoke when the engine is warm (you’ve been driving for a 10-15min) then you’ll need to get it looked at by your mechanic.

White Smoke

Unlike vapour, thicker white smoke can be a symptom of something more sinister, like a cracked engine block, a blown head gasket and coolant leaking into the engine, or the engine overheating because of the coolant leak; which is the worse of the two scenarios. This is not a fix you should attempt yourself and if you do see thick white smoke pouring from your exhaust pipe then make sure you stop driving your car immediately and book it in with your mechanic, telling them what you’ve just witnessed – you might even have to stop mid-journey and call a breakdown service. These aren’t cheap fixes and you shouldn’t ignore them – in some cases, you might end up having to replace your entire engine.

Blue Smoke

This might be something you’ve noticed with your lawnmower; I have… and it means the same thing if you see it pouring out the back of your car, that there’s oil leaking into the combustion chamber and being burned via buggered piston rings. Head straight to your mechanic. If your car is turbocharged, blue smoke can also mean the blower is stuffed.

Grey Smoke

This smoke signal suggests that your engine is possibly burning transmission fluid (you’ll likely also be able to smell the burning transmission fluid), the turbocharger (if your car is turbocharged) is faulty, or that your car is using too much oil. Either way, if your car is belching out plumes of grey smoke get it to your local mechanic.

Black Smoke

If you see thick black smoke pouring out of your exhaust pipe it usually means your vehicles is burning too much fuel. One quick check is to take a look at the air filter which might be clogged and need replacing; this is a simple DIY job, but it could also be an issue with the fuel injectors, etc. So, if you see black smoke, again, book your car in with your mechanic.

Smoke coming out of your vehicle’s exhaust system is never a good thing, but like most things, if you catch it early and don’t ignore it, then you’ll likely be able to deal with the issue before things become worse.

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