Hi Ric,
    I have noticed through much driving with a coolant pressure gauge attach
to the system at the radiator  bleed plug that the coolant pump increases
pressure by 4 psi at 4k rpm.   Or it has 4 more psi of pressure at 4k than a
1k rpm. This is on a van that seems to handle winter and summer well. This
tells me the coolant pump puts 4 psi pressure on the system until the
thermostat opens.  While cruising down an interstate I can watch the
thermostat open and close as the coolant pressure drops a bit while it
opens.
    So if you test the pressure at the front air bleed plug you should be
able to discern if the pump and thermostat are proper.
Darrell

----- Original Message -----
From: "Richard Golen" <rgolen@UMASSD.EDU>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, November 19, 2000 6:20 AM
Subject: Another heating/cooling question

> In the immortal words of one of Batman's arch-enemies...."riddle me this"
>
> My son's 84 Vanagon will overheat in the summer when driven slowly....and
> in the winter he barely gets heat. Is it the water pump....is it the
> thermostat or is it both?
>
> He's coming home from Rochester NY for Thanksgiving this week and I want
to
> see if I can send him back with a bit more heat than he's had in the past
> year or so....
>
>
> Thanks.
>
> Ric
>