I own a citroen c4 (unfortunately). On the drive home this evening (and a couple of times recently) i have been getting a warning message to stop as the engine temp is too hot. So when i got back i waited for the engine to cool, then took the cap off the reservoir to check the levels. I was horrified to see it was bone dry! However after taking the top off there was some fluid on the floor under the engine - not sure what it was or where it came from but maybe i drained the system by mistake after taking the cap off. Any advice on what to do from here would be greatly appreciated.. does it need to be checked out by a garage or just add coolant and water?