Hmm, are you sure it is the heater core and not the o-ring? Over time, 
those o-rings get very non-flexible. Regardless, when you replace the 
core, you'll want to replace the o-ring too. It's a fairly straight 
forward job. In a non-Westy, there will be a plastic box (if I'm 
remembering correctly) that covers the core. Remove that and you should 
have easy access to the core. You'll want some clamps to pinch the 
hoses down (to reduce the loss of coolant while replacing the core.)

If you are in a westy, you can pull the rear seat (procedure is in the 
Bentley) and that will give you access to the rear core.

On Dec 6, 2004, at 1:27 PM, Todd Brown wrote:

> My little heater core under the rear seat found in later-model 
> Vanagons is seeping coolant.� The Bentley manual has zero info on 
> removing/installing the core/leaky valve.
> �
> As luck would have it, I have a nice replacement core lying around and 
> want to swap them out -- anyone done it?� Do I have to drain the 
> entire cooling system?� Simply put, how large of a nightmare am I 
> looking to tackle here??!
> �
> Thanks in advance!
> �
> Todd
> 90 Carat
> �