i don't know anything about rovers, but here's my two cents any way. ;) have you noticed any white smoke coming from the tailpipe? that's a good indication there is water getting into the combustion chamber. if that's the case, it could either be head gasket, cracked head, or a crack in the cylinder next to the water jacket. now, if there's no white smoke coming from the tailpipe, you're going to have to lokk for leaks in the cooling system. wash the engine well, then check under the hood after every trip in your car. with a clean engine it's easier to find leaks. one other thing it could be is a leaking heater hose, or heater core. you should be able to smell the antifreeze/coolant if it's leaking from the heater core as those are usually installed on the passenger side under the dash up on the firewall. check the carpet to see if it's wet or smells of coolant. well, good luck to ya!