Why does my car overheat only in traffic?

Common causes include a cooling-fan fault, low coolant, restricted airflow or cooling-system problems that are less obvious when road speed is providing extra airflow.

In relation to “Why does my car overheat only in traffic?”, a warning light or new driving symptom is most useful when you record when it appears, what the car is doing at the time and whether any other warning or smell appears with it.

For “Why does my car overheat only in traffic?”, do not remove a hot expansion-tank or radiator cap. Let the system cool fully and investigate coolant level, fan operation, leaks and circulation before further driving.

For “Why does my car overheat only in traffic?”, the mechanical principles here are not unique to Northern Ireland, but the roadworthiness consequence is relevant to an NI driver. Use the vehicle handbook for model-specific instructions and the attached official sources — nidirect - The Highway Code for Northern Ireland, nidirect - MOT and vehicle testing, and GOV.UK - Vehicle recalls and faults — for legal or testing context. A dashboard symbol can mean different things between manufacturers, so the exact symbol and behaviour matter.

Practical next step for “Why does my car overheat only in traffic?”: record the warning or symptom, check the handbook and basic safe-to-check items, and arrange diagnosis if the cause is not obvious. Stop driving if there is a red warning, loss of braking/steering, severe overheating, heavy smoke, major fluid loss or any other sign the car may be unsafe.