Coolant is leaking between the firewall and the bottom of the black plastic box that the heater hoses are connected to. I opened up the glove compartment and the heater core itself looks fine. Is it difficult to remove the entire plastic box to find out what is leaking?

As a temporarily fix, could I just connect the two heater hoses together? I figure I wont need heat until September....

Removing the whole box is a pain. (dash needs to come out, or at least up)

There is a cover plate on the inside that you can take off, for removal of the heater core. Has only 3-4 7mm screws holding it in. The heater core probably has a pinhole leak in it somewhere. The cover is about 10" tall and about 5" wide, smooth, curved.

There is also a 7mm screw holding the heater core inlet/outlet pipes, on the firewall side. (that's for when you get around to taking the heater core out to check and replace it.)

You can loop the hoses. One is 5/8 and one is 3/4, but you can squeeze the 5/8 hose over the 3/4 nipple. I'd try that rather than trying to clamp the 3/4 hose down to the 5/8 nipple.