I've got a 325i 2012 and i'm wondering when the warning is supposed to come on, as last night I have to put 500ml in to bring it up to maximum. Should it have warned me?
If its same as my E46 a float inside the cap moves up and down and triggers the coolant warning light when float drops to bottom. Physically check that that float is moving ok 1/2 litre is not a lot of coolant so could be ok.
