Not always.

It is a sign of HGF, but the lack of that sign does not mean it hasn't failed.

water loss could be from the pressure cap on expansion tank. They have been known to fail meaning an escape of coolent and steam. its hard to see if it is leaking but hey at 4 quid for a new one its worth a try before you replace HG.

Early freelanders had expansion tanks that cracked around the cap. The new ones have larger caps. They are cheap to buy, even from a main dealer.