Thanks for sharing your experiences and know-how, i guess it's hard to put in a sentence or two the trials and frustrations and little victories... on closer inspection of my rad cap (the water was there, right upto the neck) i noticed the lower seal was hard with a nibble off one edge.These engines are pretty good about not overheating until there is a lack of fluid. Sometimes it takes a couple times of filling, running, and checking before the level is where it belongs, that's normal. I have had to do this two or three times with mine, but they never were low and overheated from a bubble of air, they purge really well, but levels might drop. Now that the radiator is full, add to the overflow, going above the hot line is OK, the engine has to warm up, push fluid through the overflow line and into the tank,, and there is plenty of room in it so no harm will occur, air bubbles in the hose itself sometimes give a false level, or, expanded fluid is so slow that the bubble still exists sometimes.
The one spot for a small leak is the thermostat housing. it is on the passenger side of the head, the upper radiator hose attaches to it, temp sensor is located on it, and they tend to slowly seep really slow over time and corrode. Who ever thought a steel gasket with rubber on either side sandwiched between aluminum and water going through it is a good idea, I've redone them four times on two PT Cruisers I have in the family. Last time I put a thin layer of #2 Permatex on both sides of the metal gasket to act as a shield against the steel and aluminum from contacting each other and it seems to prevent the corrosion problem.
i went to the spares shop to purchase a replacement, he gave me a 17psi??? that was slightly narrower and it rattled about in the neck, so i took it back and ordered online.
with my parkinsons wobble i would be stressing trying to do the pressure thing, so i've booked in to the test station for monday.... the level is now there, albeit the expansion is empty. fingers crossed