do you have to discharge a/c to replace the heater core?

Yeah if your heater core is inside the cab, 1. no you do not have to discharge the ac since the heater core is in the coolant system, I do recommend draining the coolant and disconnecting the lines from the engine compartment and getting as much coolant out as possible from there before removing it, and 2. that's probably exactly the reason you're smelling antifreeze is the heater core.

[quote:9701cd651b="imchuckrock"]I have a 1998 ford f150 with a 4.6 with approx 130,000 miles on it. I heard you have to discharge the a/c on it to replace the heater core. I have replaced heater cores before on other cars & trucks and never had to do this. I this correct? Also i am not positive it is the heater core but I smell antifreeze inside the truck so that leads me to belive that is what it is.[/quote:9701cd651b]

I have the same problem on my 97 with same engine, according to Haynes auto repair manual disconnecting the AC evaporater lines is part of the procedure. I came to this forum to ask the same question. More precisely I would Like to know WHAT is the WORK AROUND to avoid disconnecting AC. If its just more work I'll do it. I have changed about 6 heater cores. but this will be the first that requires a complete dash removal. for peace of mind ,I would like to know why Haynes suggests it.

There is obviously no reference to the A/C lines in those illustrations. Thanks for the quick response and the illustrations.