Chilton's manual refers you to the section on removal and disassembly of the cooling unit b/c they are integral, not separate assemblies (But there's no diagram, just the text I posted above). That procedure starts on page AC-39 of the 87 van manual and includes a diagram. There may be extra parts not in the diagram. Strange they don't mention heater core specifically.

But the starting step is to remove the glove box and under cover. Then it should all be visible and at least you can get a better look.

I know there have been other threads around people not getting heat and cleaning the heater core is something they've done. Maybe they'll chime in.

This is helpful for following your heater lines. http://www.toyotavantech.com/forum/s...-your-Vanwagon