I have recently purchased a new Ford Fiesta (not the very latest model) with a 1.0-litre Ecoboost engine. After returning from a drive around town today, I lifted the bonnet and noticed that the water in the coolant reservoir was bubbling. The fan was running. As soon as the fan stopped the bubbling stopped. Water temperature gauge showed normal and not at all raised. I haven't had a turbo engine before and wondered if this was normal.