probably a dumb question but as far as i can see there's two possible locations, one on the passenger side of the block where the sensors are (the hose that goes to the top of the radiator) and one that goes to the front drivers side of the block and comes from the bottom of the radiator.
normally i'd just pull them both off to see but i've only got one gasket and once i pull them off no way to go get another one.
cheers
Matt