http://www.benplace.com/rear_heater.htm

Leave the 2 hoses there, fill those with coolant, block them with a screw,
when pushing the screw in both hoses, the coolant will overflow. There will
be no air in the system. Even if there is a small amount, it will stay there.

The best solution, go to home depot or any other car parts store, buy 2
small valve, one for each hose, open valves, put a rag or any small
container, fill the expansion tank if not full, close it, have someone start
the van, bleed the 2 hoses, close valve.

When the original rear heater valve is close, no coolant is passing in the
rear heater,  if there is, yourt valve is finish. It won't change anything
at all in the engine temperature.

I jsut bleed a 1.9 this weekend.

I drove mine(87)like that for one year.

Now what i did; remove the heater, block the hoses holes, went camping.

Cheers.
ps.: stop worying about the coolant system, it's not a alien ship.
http://www.benplace.com/