I am installing a coolant heater for my diesel that will be running on
veggie oil (hopefully soon).  The heater is located above the rear deck of
the van about 1 foot above the engine.  I have run 5/8 line up through some
holes that I cut in the floor of the rear deck.  I plumbed into the coolant
system but can�t get the coolant to run up through the heater and back out
again(the heater is basically a little maze of metal pipe in a small area
with barbs on either end).  Now I didn�t run the van too long, probably
about 5 or ten minutes) because I was worried about overheating, but the
coolant wouldn�t run through the lines up through the heater and back down
to the system).  I know that the coolant is a low pressure system, but since
it�s a closed system shouldn�t it have to run its course?

Help.

Dave