As several people have already posted it is an easy job once you get into it.  If you are not already aware you should know that the rear seat has to be removed unless you are willing to modify the box that covers the core and blower housing.  Looking at the heater and cover from the front you will see the vent for the warm air, the plastic cover for the core and blower has a section that goes under the lower edge of the air vent thus completely surrounding said vent.  With the seat in place you can not get the cover to come forward enough to remove it unless you cut the plastic that crosses under the vent out.  Cutting the plastic is easy and will not have much effect on the structural integrity of the cover as it is screwed down on both sides.  The down side that I see to this approach is that while you will more quickly and easily get your heater changed you will not be able to clean up the leaked coolant as well.  I have replace the cores on both our Westy Syncro and my G
L Syncro and on both of them I pulled the rear seat completely so that I could mop up the coolant underneath.  Should you choose to pull the seat it is not hard as it is held in by four bolts(two per side).  Make sure that you get both a new heater core and the valve Oring as it will be brittle and in need of replacement.

Mark in AK

----- Original Message -----
From: Jamie McMahon <jamie_m@COMCAST.NET>
Date: Wednesday, February 21, 2007 2:08 pm
Subject: Help.. replaceing rear heater core 87 Vanagon GL
To: vanagon@GERRY.VANAGON.COM

> I am going to be changeing the leaking rear heater core in my 87
> Vanagon GL. What I need is some tips on doing it correctly. I have
> checked the archive and did not find much info. Do I need to bleed
> the entire cooling  system after I do it? or can I just bleed it
> at the core? If someone could point me in the right direction it
> would help me greatly. The concept of coolant in my bus is a new
> thing for me. I am new to the list and this is my first Vanagon.
>
> Thanks, Jamie
> 87 Vanagon GL (Boo Boo)
> 73 Westy (Pumpkin)
>