Originally Posted by charmalu

Do the pressure test that NHDOC recommends to do. If you discover that the heater core is leaking, you will have to remove the Dash and get into the heat A/C box . It is quite an involved job.

DMORRISON has a good write up on getting in there. this is for replacing his Evaporator, but the Heater Core is close by.

http://www.peachparts.com/Wikka/W123Evaporator

Hope it is something else,

Charlie