hi I'm a new owner of a 2001 td5 defender and on the way home the temp quage was all over the place and then eventually stopped working because of lack of water when I got home I let her cool down and the gradually added around 6 ltr of fresh water and the quage kicked back in.. Just wondering if anyone has any information regarding what this could be.. there is a light oil leak on the engine cover and looks like it was an advisory on the new mot. thanks for your time Neil...