----------------------------
Hi Brian,
    I had the same question as you as it didn't seem to do much when open or
closed.  When I replaced the coolant  hoses on my 86 I found opening the
thermostat bleeder valve allows air and or coolant  from the thermostat
housing to travel up the hose attached to it and  into the coolant  pipe
that sits around the  top of the engine.

Darrell

-----Original Message-----
From: Brian Doss <BDOSS24046@AOL.COM>
To: Vanagon@VANAGON.COM <Vanagon@VANAGON.COM>
Date: Wednesday, July 08, 1998 6:47 AM
Subject: Question: bleeder on thermostat housing

>my '88 has a "bleeder screw" which is a knob on top of the thermo housing.
In
>the Bentley book, it says to open this knob by turning counter clockwise
>before and during filling the cooling system. Well, at no time during the
>process did I see any coolant escape from this bleeder, so what is it's
>function, and should coolant escape from here in a properly air-purged
system?
>