Heater core for 1956 Thunderbird
 

I could have sworn I posted this earlier but can't find it, so I must have hit the wrong button.

I plan on installing a new engine/tranny into my 1956 Thunderbird in the near future. I happened to notice the heater core on the firewall and was wondering how does one test a heater core to tell if it should be repaired or replaced? Can it be tested while still on the car? Does it need to be pressure tested at a radiator shop? I don't know the history of this core, but it looks to be in good shape from the outside. It did have both heater hoses attached to it before I removed the old engine. I don't know if the heater worked before I removed the old engine. Any advice would be appreciated.

Re: Heater core for 1956 Thunderbird
 

A friendly radiator shop may test it for you for free?
(hoping it leaks so they can charge you to fix it)

I dunked mine in a bucket of water and blew some air into one tube, with a finger over the other.
Normal operating pressure is 13 psi max.
Knowing that it was hooked up before is a good sign.

Re: Heater core for 1956 Thunderbird
 

I second this method! plug one of the tubes with a rubber stopper or your finger, place in a bucket of water and blow 12-13 psi into the other tube by setting the air compressor down. You can also do the opposite and fill with water and blowing the air in and seeing if any water leaks out but air bubbles are much easier to see!

Re: Heater core for 1956 Thunderbird
 

I rigged up an old radiator checker to test my '59 Ford core. It held 20 psi for 10 minutes, good enough for me. Funny that the core itself looked absolutely new being housed in the heater box.