Wilbur,
I've had an EMS (http://www.littleblackbox.co.za/html/little_black_box.html) fitted to my TD5 110 for about six years now and it's probably saved me a serious amount of cash already on four occasions. It picks up coolant leaks very quickly (even when a radiator hose or the blanking plug at the back of the oil cooler fails) and shouts loudly. No problems with the float or expansion tank at all.
Derrick