I'd like to share something that someone on this list shared with me years
ago. This is done after you've done all the "jack-up-the-front" stuff from
Bentley, etc.  After driving the van to full temperature let it cool down
overnight. There will be some air in the rear reservoir.  Open it up and
fill it with coolant again. Drive it again until it's hot then let it cool
overnight again. There will be more air there. Fill it back up. Keep doing
this for about a week or until air stops appearing in the tank.  After I did
this the temp gauge is always below the led when I'm driving and when it
idles it only goes a hair passed the led even on hot days. The light has
never blinked.  I'm convinced that most head problems people have are from
too much air in their systems.

Bryan