All Defender drivers should take note of what happens to your head if you only use water in the radiator. Not using the right fluid as stated by LR will damage the head like in the pictures shown. Water tends to rot away the alloy head which then leads to you getting hot water spat out of the fluid reservoir unit. It comes out as a brown rust coloured fluid.
So if your motor keeps needing a fluid top up you ay have already had the same issue as i i had. You can see the holes that happened in the pics.
What happens is the cylinders pump pressure into the water system as the holes then eat away at the head gasket and the gap then allows the compression to pump the fluid through the water ways up in to the header tank on the dash at the top of the engine bay. The engine ran fine, started OK etc but was losing fluid and i had some brown rust coloured fluid marks on the engine etc.
So, i spent £1300 on a new head made in Spain and having it fitted. Dont make the same expensive mistake folks and use the right fluid which isnt tap water or distilled water and its an orange colour.
I inherited the problem with the vehicle and now always use the right fluid not plain water!!!!!!!!!!!!