hi i have a defender 90 td5 its dne 125000 miles i have been having trouble with the cooling system it keeps spitting the coolant out of the bottle when it gets up to temp i have changed the water pump, thermostat, top rad hose, radiator, bottle cap,and going to change the heater matrix tomorow has any one had this problem or got any ideas what ealse it could be is there any chance the head gasket could be doing this its doing ma fookin head in