Could well be - you can get pink coolant if you mix two particular brands apparently. How old is your Beamer? You can get a suspension of rust in the coolant too, which makes a scummy brown layer. Check your dipstick and see if the oil looks ok and is at the appropriate level. Head gasket failure usually shows up a funny white scum in the coolant as far as I know. Possibly drain the coolant and fill back up with only one type to see if it happens again.

Edited by Bobbin Threadbare on 14/06/2011 at 12:42

Why did the turbo fail? The turbo is water cooled-if it failed, oil could have mixed with the coolant. Alternatively, your oil cooler might have sprung a leak allowing water and oil to mix.