If the car has been parked outside, could it be attributed to water that has frozen and them thawed as you drove the car?
Parked in a garage (albeit unheated so probably very cold
). The steam didn't smell of anything so after my initial panic that the car was on fire (and the OH thinking it might have been the clutch), we figured it was probably just water + A/C because it was odourless.
BTW thanks for all your suggestions on coolant levels etc - it's been a bit too cold to venture outside so I haven't checked the fluid levels yet.
