What Your Exhaust Smoke Colour Is Telling You

A little vapour from the exhaust on a cool morning is normal. Thick, coloured smoke usually isn't. The colour gives a strong clue about what's wrong.

Thin white vapour

A thin, wispy white vapour that disappears after the engine warms up is usually just condensation. It's normal and nothing to worry about.

Thick white smoke

Thick, billowing white smoke that keeps coming after the engine is warm, often with a sweet smell, can mean coolant is being burned in the engine. Possible causes include:

• Blown head gasket

• Cracked cylinder head

• Cracked engine block

Other signs include losing coolant with no visible leak and the engine overheating. Stop driving and get it checked to avoid severe engine damage.

Blue or grey smoke

Blue-tinged smoke usually means the engine is burning oil. Common causes:

• Worn piston rings

• Worn valve stem seals (often more smoke at start-up)

• A faulty PCV system

• A failing turbocharger on turbo engines

You may also notice the oil level dropping between changes.

Black smoke

Black smoke means the engine is burning too much fuel, a rich mixture. Possible causes:

• Clogged air filter

• Faulty MAF or oxygen sensor

• Leaking fuel injectors

• High fuel pressure

On diesel engines, some black smoke under heavy acceleration can be normal, but a lot of black smoke means something needs attention.

What to do

Note the colour, when it happens (start-up, acceleration, all the time) and any smell. Then have the engine diagnosed. Catching problems like a failing head gasket early can make a huge difference to the repair bill.

Need help with this? RCJ Mobile Mechanics comes to you in Portmore, Spanish Town, Kingston, St. Andrew and across St. Catherine. Call or WhatsApp (658) 207-6565 or book a mechanic online.