hi, I have a 2011 c-max diesel auto, for over a month now i have been plagued with coolant loss! in 400 miles i have topped it up with nearly 5 litres of coolant! no signs on ground (constant wet weather doesnt help) oil seems ok , no signs of wetness inside car! been back to evans halshaw 3 times now , they cant find it !went in again yesterday , could not find it.. booked in for extensive investigation on the 21 august,( having to have a courtesy car !) has anyone any idea?