Hi Vince,

    This is Tommy, you may need to plurge the air out of the system, and
actually be running low on coolant. Its worth checking anyway.
    With a helper, first you need to raise the rear of the van, (be safe,
use stands) on the upper right side of the radiator there is a bleeder
screw. Have your friend holding the idle from inside the van, at about 1500
RPM's, add coolant to the fill tank untill all the air is forced from the
bleed screw, tighten the bleeder, top off the fill tank, and replace the
cap, only then lowering the idle.
    You may have another problem but I would check this first.

Tommy
Volkswagen Restorations USA
www.freeyellow.com/members7/volksfix1/