Had the low coolant warning pop up last night on the way home. Went to check the level and top up to find that a level wasn't easily readable on the reservoir! The coolant inside isn't pink or indeed purple but a weird brownish colour (it isn't sludgy and doesn't appear to contain oil) the bottle also looks like there's quite a bit of scale on the inside of it all too, especially on the level sensor as well as minor sediment particles. The car has done 13k miles and hasn't really seen any abuse in my ownership (from 2k miles). The car is booked in for investigation with the dealers under warranty. Has anyone else had this issue or heard of anything similar? Car is totally stock, it hasn't ever to my knowledge overheated and the oil is spotless and on level.