Cooling system bleeding question.

Hi Guys,

Can I pick your brains?
Went out for a short run locally yesterday around the Chepstow area.
I had just completed my transmission oil change with Redlne MTL and wanted to splash it around the gearbox!
All was going well until I hit some slow moving traffic which became stationary.
Long story short.....I overheated and conked out. (Left it for 40 minutes to cool down and made it home no problem)

I'm thinking that it could be simple and I have air in the system which I need to bleed out. I may of caused this when I worked on the carburettor strip down as I disconnected the small hoses to the auto choke....would this do it?
So, the bleed point on the radiator in the front boot hinge is proving to be impossible to access. (For me anyway)
I had an idea to jack the rear of the X1/9 as high as I could, remove the coolant expansion tank lid, open up the heater controls and start her up.
The expansion tank being the highest point would mean any air in the system would exit from there wouldn't it?.....am I correct?

I did this and had the X1/9 idling for almost an hour on my driveway jacked up and couldn't get the temperature needle to even go horizontal and hit 90 degrees.
Would I have cured this now?

One suspicion I have is that when I overheated in the stationary traffic, I was on a steepish hill.
Would this have made any trapped air in the system migrate to the radiator reducing the coolant going through it and raising the temperature?

Any input would be really appreciated.

Gaz.

ive just flushed my coolant and i bled from the carb hose the top one , i undid the hose let engine run and kept the expansion tank topped up as cooa lant came out the hose with a steady steam , ive taken it for a run and it seems ok