Car · Problems

White smoke from exhaust

A little vapour on a cold start is normal and clears within minutes. Thick white smoke that persists when warm is not.

UrgencyModerate
Can I drive?Yes, carefully
Likely causesHead gasket

Likely causes

  1. Head gasket40%

    Thick sweet white smoke, mayonnaise under the oil cap and coolant dropping with no visible leak.

    Garage price: Head gasket £590 – £1,560
  2. Dirty or faulty injector25%
    Garage price: Diesel injector £245 – £650
  3. Glow plugs20%
    Garage price: Glow plugs £105 – £355
  4. Clogged EGR valve15%
    Garage price: EGR valve £275 – £740

What you can check yourself

  1. Watch the coolant level over several days.
  2. On a diesel, acrid white smoke at start-up points more to glow plugs or an injector.

Fault codes often linked

P0093 Fuel system large leak detectedP0171 System too lean (bank 1)P0172 System too rich (bank 1)P0175 System too rich (bank 2)P0201 Injector circuit, cylinder 1P0300 Random or multiple cylinder misfireP0301 Cylinder 1 misfire detectedP0302 Cylinder 2 misfire detected

Frequently asked questions

White smoke from exhaust: what causes it?

Likely causes: head gasket (40%), dirty or faulty injector (25%), glow plugs (20%).

Can I drive?

Yes, carefully. Urgency: moderate.

Indicative estimate. MecaScan cannot see your vehicle: always have a diagnosis confirmed by a professional, and never work on brakes, steering or airbags without the skills.