Coolant keeps disappearing with no visible leak

Last reviewed 14 August 2026 · OBDCode UK editorial

ungraded — treat as general guidance

Can you keep driving?

Do not drive with the cold level below the handbook minimum, a rising temperature, steam, or a coolant warning. If the engine is fully cold, the level is correct and there is no warning, limit driving to a short essential trip to a nearby garage. Never remove the pressure cap while hot.

Checks you can make without dismantling anything

• Only when the engine is fully cold and the car is level, view the expansion-tank level without opening a hot cap.
• Photograph the cold level on different days from the same angle.
• Look from outside the vehicle for staining, dampness or a fresh puddle; do not crawl underneath.
• Record cabin misting, a sweet smell, persistent exhaust vapour and temperature warnings for the garage.

Stop and arrange recovery when

• The temperature rises or a temperature warning appears.
• The level is below minimum when cold or drops quickly.
• Steam appears, the cabin fills with mist, or coolant reaches a tyre or the road.
• You cannot confirm the correct coolant or safe cold-check procedure from the handbook.

What to tell the garage

Provide cold-level photographs, the top-up history, temperature behaviour and where any staining or dampness appears.

UK cost

We don’t have a verified UK price range for this job yet. Ask for a written estimate that separates diagnosis, parts, labour, VAT, fluids and any calibration.

Related guides

• Car overheating even though coolant looks full
• Exhaust smoke colour triage
• Head-gasket quote questions

Sources

• The Highway Code — breakdowns and incidents · grade A · accessed 12 August 2026 · supports safe stop, recovery
• DVSA MOT inspection manual for private passenger and light commercial vehicles · grade A · accessed 12 August 2026 · supports mot

General guidance, not professional advice.