I agree, Sam. I have done it both ways, no difference noted. The heater
hose "T" connectors have a smaller feed pipe inside diameter on the legs
that go to the rear heater than they do on the legs for the front
heater. Only about 6mm or so, versus about 10mm for the front heater
feeds. In any case, a tiny opening compared to the main coolant passages
to the radiator.

Any Vanagon cooling system that depends on blocking that tiny 6mm bypass
needs repair IMO.

Mark

Sam Walters wrote:
> ...
> Basic physics - larger pipes and openings have much less resistance than
> smaller ones.
>
> And the much larger pipes and hoses carrying coolant to the radiator
> offer significantly less "resistance" than the smaller hoses going to
> the front and rear heaters.  While some of the coolant will flow through
> the rear heater hoses if they are left in place connected and thus
> return to the engine without having been to the radiator, all of it will
> not circulate through there and bypass the radiator.  Given the size
> differential of the pipes,  most of it will go to the front and the
> radiator as that is the path of least resistance.  Coolant will still
> flow straight through the T toward the front heater even though some
> will make the 90 degree turn into the rear heater loop.
>
> In addition to thinking about it from a physics perspective, I have some
> practical experience:
>
> Some PO (2nd back I think) took the rear heater out of my 85 weekender.
> The hoses are connected under the rear seat with a short metal bypass
> tube.  The van runs very cool and the front heater works fine.  In fact,
> it seems to heat up the front as fast as my other vans.  Didn't miss the
> rear heater this past winter but had thought I would.
>
> ....