I am getting a coolant leak inside the car from under the dash whenever I nail the throttle after running 5-10 minutes. - I am assuming it is right at the hose connection. I am not sure if this is a pressure thing or a airlock situation.

What I would like to know is can I drop the heater box from under the dash without removing the dash itself. I had restored the core box and did a pressure test of the heater core itself. The removal and install was done during a car strip down stage so nothing was in the way. Now I am assembled.

thanks

What car?

And I doubt that it is a connection leak? and not a air lock issue.
More than likely it's a rotted out heater core. Always replace them when you have the box open. They don't last forever.

I agree, doubt it is connection. And even a newer core could be leaking if it is Chinese junk. I haven't accessed a lot of them but the ones I have on my M and F body Mopars require pulling the dash.

Sorry

It is a 70 roadrunner
As mentioned I did pressure test it and did not see any signs of rot, I believe it was original and not import. Anyways that is why I was thinking connection but if the dash has to be pulled I will bypass for now and what till the snow flies.

thanks

does anyone know what I need to remove to get to this heater core?
remove windshield & dash?
remove the core box from under the dash?
remove just the heater core from the box? How

thanks again

Can't help on a B body, but my Dart and my Diplomat did NOT require pulling the dash to drop the heater box. Might be wise to invest in a factory service manual as it will detail this chore nicely.

If its a leak at the connection point give the hosa clamps a little tightening and re-check... better yet, get some new heater hose and re-check. If its a core leak, the box needs to drop. On mine ('70E w. AC) it can be done with dash in. Agree the FSM is your friend on this.

The heater box will come out from under the dash, pull the glove box out. probably take the passenber seat out as well to get some room.
then take the box apart and clean and replace the core, reinstall.

I removed mine in my 69 Sport Satellite many, many years ago. I didn't remove the passenger seat but that would have made it much easier. The entire heater box will come out as a unit, then you can tear it down and make your repairs. Mine is a A/C heater unit and I'm assuming it should be the same. I was just a dumb kid and managed it, so you should have no problems. It does help to label the electrical and vacuum connections if yours has them. Take pictures also. All those things I didn't do, but it was around 1978 and times have changed.