V6 gurgle noise behind the dashboard centre?

[biffa75]

Hi folks,

I decided to take the 75 out this morning tondo the family shop and with gentle revs around 1500rpm a water gurgling noise could be heard behind the centre of the dash.
Haven't noticed the coolant level drop. Tried looking into the V of the engine, can't see a great deal but possibly slightly damp but can't say if it's coolant.
After a short run of about 13 miles i couldn't hear the gurgle anymore. Is it normal? Or airlock in the matrix?

Thanks in advance

Rob