I have a 2011 328i 3l convert/hardtop.  I have had nothing but rotten luck the past 3 months with this thing.  All the previous post were because I bought a brand new starter that was no good.  I assumed it was because it was new in the box.  Just because it's new don't mean a thing.   So now to the present mess.  I got it all back together and cranked it and she run fine so I drove it to the store.  When I got back and pulled into the drive I heard a loud spraying sound and steam coming from the hood.  I shut it down opened the hood but saw nothing but a little steam.  Then all of a sudden a blast of steam comes out of the left side of the motor towards the front and it blast then quite then a couple of seconds latter it did it again and it sounded exactly like a pressure relief valve.  I'm praying that there is one  because if not and it not some sort of hose then guess what (head gasket).  But I have been working on motors for over 50 years (mostly 50's & 60's & 70's) but I have never seen or herd of this.  Does anyone know what it is?  It was late and I have not taken anything down to see what it might be.     Thanks Roger

Morning Roger

Sorry to burst your bubble but no pressure release valve. The cooling system is a sealed system take a look at www.realoem.com either select your model or put the last7 digits of your Vin into the search box. Then search the relevant section, it will show you the parts and where they fit.

My guess would be a hose or "O"ring split and low coolant level maybe a gasket (water pump or thermostat seal) If the system was full there would be signs of a leak somewhere (white residue) around or near the leak.

Dave