Spitting Anti-Freeze

Where from? Are you sure it is anti-freeze?

Why not just have your car towed to the nearest independent repair shop or BMW dealership to have it examined by a competent mechanic. Then you will know exactly what is wrong and can get it repaired. Its pretty obvious you are not going to fix your own car, so get it done, NOW!

"Just changed the anti freeze." Did you change the thermostat too? It sounds like you might have put the tstat in backwards and now it doesn't open properly. The result is overheating.

Spitting out antifreeze is the affect of the problem you are having, getting to the bottom of the Error Message will fix it.

Sounds like there is a fair amount of pressure in your cooling system. Does the pressure stay up after you have switched off the engine?

Usually this points to a blown gasket. Cylinder pressure manages to get into water ways and pressurise the cooling system, causing leaks and or bursted water pipes. Hope for your sake the problem is less serious though.

If it is a blown gasket, make sure you have the cylinder head skimmed before replacing the gasket. Actually, have the cylinder head checked out by a specialist and overhaul it while you have it off.

MW

Resulting in warped head, blown gasket etc. etc. Expensive bit of DIY?

No did not touch the thermostat simply put new anti-freeze in.

must be an air lock (through the heater) then?

The M20 has a bleed valve in the top of the thermostat housing - maybe the M30 has the same thing? The radiator on mine also has a plastic bleed screw in the top so that the coolant will get to the top of the engine. I know from experience that if you don't bleed the M20 properly when changing the coolant then you're asking for trouble from the inevitable air-lock which will be in there. I seized the engine, wrecked the pistons and warped the cylinder head shortly after changing coolant for the first time on a BMW resulting in a $300 repair job. A slant 6 can be a real learning experience.

Steve