I just replaced my rear heater core and the valve o-ring is round.  I also
ordered a new o-ring before I bought the heater core thinking it might fix
my leak, and it was round.  My original heater had a flat seal.  I
personaly like the o-ring better as it has a little more "give" to it when
tightening the plastic/nylon bleeder screw than my original with it's flat
seal which was made of a hard material.  I was always scared of snaping the
bleeder screw off, so I also bought a spare bleeder screw and it also came
with an o-ring.  I do not know the size but it is a pretty tight fit on the
bleeder screw.

Pascal
'84 Westy

On Sun, 26 Sep 2004 18:45:28 -0700, Shawn Wright <swright@ZUIKO.SLS.BC.CA>
wrote:

>Can anyone tell me whether the rear heater valve O-ring for an '88 Vanagon
>might be a common size? Part # 861 819 297
>
>Mine is brittle and cracked, so it's hard to tell the size of the
original - if I can
>get one locally it would save me some time...
>
>Thanks.--
>Shawn Wright
>http://Zuiko.sls.bc.ca/swright
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