Sh*t!!! I've just read this, I hope this doesn't apply to us? : ( "Firstly, no - its not normal. As long as you are not overfilling the bottle, then you've got a leak. Is it wet ever under the expansion tank? check inside the oil filler cap - if you see a milky residue, then its either head-gasket or oil cooler - same if you see an oily film inside the water tank. if you can hear water bubbles gurgling when sat in the car with the ignition turned on after you have heated the engine up, then this points to a head gasket. I have a tool that sniffs the air in the water tank for combustion gases -