Freelander 1 2.5 v6 air and bleeding coolant trouble

Hey guys
My first post on here I will introduce myself just in desperate need of a little help.
I have just replaced the thermostat housing on the v on my engine due to a coolant leak.
I have refilled the expansion tank and the coolant seems to disappear from the tank it’s got a good 5 litres in there. If I heat the engine up and undo the cap it floods back in but as soon as I do the cap up tight it disappears again. I’m puzzled. I think I can hear air in the system sounds almost like sand grains shooting through the coolant pipes. The lower radiator hose is cool and the top one that runs above the radiator gets pretty hot. I can see the bleed screw at the bulk head and I have undone this and I had quite a lot of bubbling but then a event stream. Am I doing something wrong here

thanks guys

First off, don't run the KV6 with low coolant, as the head gaskets go almost instantly.

Second, don't bleed the coolant with the engine hot.

Fill the tank almost to the top with coolant, then undo the bleed point by the heater, until only coolant comes out. Make sure you keep the coolant tank up to the max mark, or just above. The higher the coolant level in the tank, the more pressure there will be to push trapped air out.

Once you have just coolant coming out the bleed point, then start the engine for a couple of minutes, then stop it an bleed it again. Keep repeating this until no more air comes out.

The rest of the air in the system should purge out in time, sometimes over several weeks.
The KV6 isn't an easy engine to bleed, and some are worse than others.

Ok thanks. As I’ve already got coolant in there so I just add more then