I have an '84 Westy that I recently bought.  Previous owners repair
bills showed varitey of cooling problems.  84,000 miles and it
appears no major engine work has been done.

Drove it from San Francisco to Vancouver last week, every couple of
hours the temp gauge would go "off the chart" and the red LED would
be blinking, mostly while going uphill.

I would stop and check, coolant didn't seem to be leaking out of the
system, but the EXPANSION TANK would be empty!  (the refill tank
would be fine).

Now here's the weird part, I would loosen the cap of the expansion
tank a bit and air would seem to rush out then coolant would rush in
FROM THE ENGINE, not the refill tank.  Once the expansion tanks was
full, I would close the cap.  (the refill tank level would barely
change in this scenario).  After a cool down period, I could drive
again for a couple/few more hours.

Note, the refill tank and hose seem to be working, because at other
times the coolant level of the refill tank goes up and down as one
would expect.

The rad fan works, but it doesn't come on that often.

Before leaving on the trip I bled the system.  I'm concerned that I
didn't bleed it well enough or that air is getting into the cooling
system from the combustion chambers.

Ideas?  Advice?  This is my first water cooled van and I'm stumped.....