heres the story- took out the heater core - found out it wasnt nearly as daunting a task as the repair manual indicated- did not have to remove the entire dash assembly after all! anyway, the core did not have a leak after all (thanks Paul for a great test procedure!) so I went to reinstall, and decided to search for new O-rings that seal the heater pipes to the matrix. I found some I thought were suitable, but the pipes leaked like crazy. the ones I bought at a premium from LandRover dealer also leaked, and now I am faced with the quandary of what to do. The replacement heater matrix allegedly will not leak at the joints, but there are no guarantees. The reason the dealer says the joint may leak is because the holes that the pipes go into are scarred and one is slightly out of round. Anyway, anyone faced this and solved it cheaply (less than $190- the cost of the new heater core)
-robbie