p38 coolant drama's

hi, i've got the p38 2.5 DHSE, obviously it has issues! problem number 1:

After going for a decent drive it likes to kick the coolant out of the expansion tank leaving a rather nice puddle on the floor. It drives fine and i had a new rad, water pump, thermostat and expansion tank cap in the summer. there is no coolant in the oil or vice versa so dont think its HGF however could be wrong.

Problem number 2:

usually only happens with cruise control but on occasions it has happened when not using CC, the engine dies for about 5 seconds when coming out of CC or when its in offload, but after the 5 seconds the engine comes back to life and all is fine again. its quite strange

Any one have any ideas?
Thanks in advance

First problem could be air in the system or the expansion cap not screwed right down, mine is very tight for the last few turns.
Second problem I would be looking at the crank sensor, you need to get the fault codes read. The ECU uses 2 signals to know the engine is running, the crank sensor and the needle lift sensor on injector 4. The fuel is shut off on the overrun so no signal from the lift sensor, therefore if the crank sensor is playing up the engine will shut down on the overrun.

Whats the best way of getting air out the system?
I read somewhere to just let it run for 1/2 hour with the cap off, do you think that will sort it?
And yeah i think i am going to have to get the faults read on it, i had a feeling it would just be a sensor, well i hope it is anyway!

Squeeze and release the hoses vigerously with the engine idling and the cap off.

If you have still got your cooling problems after what has been suggested I would pressure test the cooling system.
You can get a kit which puts pressure on the expansion tank with a small hand pump. It is a BMW screw fitting and I would guess they are cheap and readily available in Germany.
It won't tell the full story but if it won't hold pressure it will point you towards leaking head gasket or cracked head.