Hi... ok ...i believe your problem IS an air pocket in the system. Many of us have been in your shoes and after lots of trial and error and effort i am sure this is the problem. I have solved it in my 92 and have had no overheating in 2 years. Here s what to do;
1 when cold in morning...top up at rad cap{which is not on rad or expansion tank but above water pump}
2 do this every morning untill you don t need to
3 all levels should become normal and therefore ....overheating problem solved!
....keep us posted as to your progress