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Engine & running faults

White smoke from the exhaust

Colour, smell and whether the smoke clears once warm are what separate normal condensation from a coolant or fuelling problem.

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Symptoms drivers describe

  • Thin white vapour that clears within a minute or two
  • Thick white smoke that continues when warm
  • A sweet smell to the smoke
  • Coolant level dropping with no visible leak

Possible causes

  • Normal condensation on a cold start
  • Coolant entering the combustion chamber, for example through a head gasket
  • A failed injector on a diesel giving unburnt fuel
  • Glow plug faults causing white smoke on cold start
  • Oil or fuel dilution in the engine

What you can do

  • Check the coolant level once the engine is cold
  • Do not keep topping up coolant without finding the loss
  • Stop driving if the smoke is heavy or the temperature gauge is rising

How we check it in the workshop

We check coolant level and pressure, test for combustion gases in the coolant where appropriate, and read fuelling and glow plug data on diesels.

Is it safe to keep driving?

Depends on the cause. Continuous white smoke with coolant loss should be treated as urgent to avoid engine damage.

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How we can help

Engine DiagnosticsEngine faults are usually a chain of events rather than a single broken part. We test fuelling, ignition, air, compression and control signals to find where the chain breaks.Read more Cooling System RepairsOverheating is one of the few faults that can turn a modest repair into an engine rebuild in a matter of minutes. Stop and call rather than pressing on.Read more Injector Diagnostics & Injector-Related RepairsInjector faults imitate a lot of other problems. Testing the injector data before replacing anything avoids fitting expensive parts the engine did not need.Read more

Engine & running faults

Other symptoms in this group

Car stuck in limp modeLimp mode is a protection strategy, not a fault in itself. The control unit has seen a reading it does not trust and has reduced power to keep things safe.Read more Blue smoke from the exhaustBlue smoke points at oil reaching the combustion chamber or exhaust. When it appears — start-up, overrun or under boost — narrows the cause.Read more Black smoke from a diesel exhaustBlack smoke is unburnt fuel. On a modern diesel with a DPF it usually also means extra soot heading into the filter.Read more Car losing power when acceleratingLoss of power is either a fuelling, air or protection issue. Live data under load is what separates them rather than guesswork.Read more Car cutting out while drivingIntermittent cut-outs are among the most important faults to record properly, because the evidence disappears the moment the engine restarts.Read more Car overheating or temperature gauge risingOverheating is one of the few faults where what you do in the next few minutes decides whether it stays a small repair.Read more

Want this looked at properly?

Send us your registration and describe the symptoms — we will tell you what the next step is.

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