I have a 03 Land Rover Discovery. Last month it overheated. My husband put plain water in it and it didn't overheat again until yesterday. When I got home I noticed that it registered near the red line but not on it. What do you think the problem could be? Any input would be helpful so that I could give my husband some ideas because I know he'll try to fix it on his own if he can. He's very good with vehicles but this is the first Land Rover he has ever worked on. He'd kill me if he knew I was asking this qeustion. LOL. He's a man's man. Thanks.