If you turn on the heater fans, you do remove additional heat from the
engine. Both due to increased cooling capacity and the fact that the
heater loop is before the t-stat. However, if you do not have air
flowing over the heater cores, there is no cooling effect and any water
flow through the cores is water flow not available for the radiator.
Normally, this does not make much of a difference if noticeable at all.
The water flowing through the cores does wear the core and each time the
core heats and cools will take away some of its life. So, if your
cooling system is working properly, close the valves. Save the cores.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Robert Cardo
Sent: Friday, June 10, 2005 2:27 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Rear heater core during summer

<<THX0001@AOL.COM(George�Goff) Date: Subject: Re: Rear heater core
during summer
In a message dated 6/9/05 11:47:50 PM, dhaynes@OPTONLINE.NET writes:
<< Close it. Any coolant flowing though the heater core is coolant not
available for the radiator. >>
Exactly. I once notice a slight increase in the indicated operating
temperature during the winter months which I eventually confirmed to be
caused by the shunt through the heater core.
George>>

Pipe dream.
Bad info.

If in fact my vehicle ( any of them ) is running hot durring the summer
months, and possibly even stuck in rush hour traffic, an old trick of
the trade is to turn on the heater fans, whch will assist in cooling the
overheated coolant.

More radiator mass, more cooling fan to the larger mass makes for a
quicker cool down .

Less coolant for the radiator?

Nope.

If the system is bled properly the amount of coolant will be exactly the
same in the radiator, as in the whole system, with or without the front
and or rear heater valves open.

Good mind twisting material though.
You guys actually had me thinking on this triva.