Start the car from cold
Starting the car from cold will help you detect potential issues that a warm engine can hide. A “cold start” simply means the engine has not run for several hours – ideally overnight. Many faults, from tired batteries to worn engine internals, are at their most obvious in the first minute after a cold start, which is why some sellers warm a car up before a viewing. When you arrange to see a used car, ask the seller not to run it beforehand, and touch the bonnet when you arrive: if it is warm, ask why.
What to look and listen for
- Slow or laboured cranking – if the car struggles to turn over from cold, it may need a new battery, or the alternator may not be charging properly. Alternatively, there could be a problem with the starter motor.
- Rattles and knocks – a brief rattle on start-up that disappears can indicate timing chain or tensioner wear on some engines; persistent knocking is more serious.
- Exhaust smoke – a puff of vapour on a cold morning is normal, but ongoing blue smoke suggests the engine is burning oil, and white smoke that smells sweet can point to a head gasket problem. Black smoke indicates over-fuelling.
- Warning lights – all dashboard lights should come on with the ignition and go out shortly after starting. Watch for the battery, oil and engine management lights in particular.
- Uneven idle or stalling – a healthy engine should settle to a steady idle quickly, even when cold.
A cold start costs nothing and takes two minutes, yet it can expose problems that would cost hundreds or thousands to fix. Combine it with a full car history check before you commit to buying.