I had some wierd issues with the BMW last week regarding the Heaters (not blowing hot) and also the car started to run a little wierd (plumpish) for a few miles while driving then it went back to normal, it happened twice in the space of a few days. I opened up the bonnet and found my new air filter had fallen off, so this solved 1 problem, I now put the original back on and its fine and running really smooth again.
I am 100% sure that the problem with the heaters is an air block somewhere in the coolant system, there must be air bubble somewhere, I have tried to solve it by letting some air/pressure out and it seems to have worked and the heaters now work alot better but only when i'm driving fast, when stationery the air blows luke walm/cold. The car has never overheated and has always run on normal operating temperature.
Its still under warranty so I can sent it to the dealer to sort out but I can't be asked to take it in, so I thought I would just do it myself and do a proper job. I don't think they put anti-freeze in and just put water and thats why the sensors are not working when they supposed to. They had it previously for 4 days but I don't think they spent enough time on it to solve the problem so I requested the car back as I needed it.
So I am going to do a coolant flush/drain and refill and hope that it will fix the problem.
Any advice anyone can give me on the coolant change before I start it later today/tomorrow morning would be great. Thanks