fill the header tank right up and try to raise the front of the car and run it with the cap OFF up to temp and keep it toped up, rev it up a few times and wait for the thermostat to open fully all the air should come out that way but I understand it can be a long job especially on the 24 v. When its all done adjust the level of the header tank to correct level and refit the cap.
Some cars have a bleed valve/opening in the highest cooling hose which is opened when re-filling the cooling system, all the air escapes and when the system is full of water the valve can be closed.