The old heater core is out - it had a small leak. Luckily the coolant did not drain into the car but escaped through the drain hose on the firewall.
My friend Lucky working in the wheel housing…
Fusick offers a perfect reproduction of the original ribbed GM heater hoses. The original heater hoses had 5 ribs just like these super nice reproductions.
I re-connected the new heater core to the cooling system and used correct reproduction heater hoses to connect the original heater valve which is still working perfectly. The hose clamps are not the correct ones yet. I think there should be tower style hose clamps which I do not have at the moment. There is still an original one on the bottom of the valve and also one on the other heater hose, thats why I´m very sure that the other two clamps should be tower style as well. I have not found a perfect reproduction clamp yet, but I´m still looking…
The dash removed. The radio is also out for repair.
There are metal clips inside holding the left A/C hose in place. You have to reach in and unclip them.
You will have to remove this support bracket.
Recirculation door - un-plug the orange vacuum hose.
You have to remove these 4 screws/nuts on the firewall. You can access number 4 from underneath the car only. Number 3 is hidden underneath the cables.
The number 4 screw on the cowl is holding a cable clip in place and the other end is the right bottom screw of the heater box - you need a second person with a 7/8 wrench to release it from the side under the car while you unscrew it from inside the car with a 3/8.
Once all the screws are off you can carefully remove the box. You have to slip it to the passenger side to get it out.
The old core in the heater case.
The 1974 Cadillac heater case and heater core. You can see the two mode doors here and on the right is the recirculation door. The thick hose on top is the aspirator hose going to the temperature sensor in the dash.
This is where the old core had developed a leak.
The old core still in place. Note the rubber seals on the tubes of the heater core. You have to move them over to the new core.
The new heater core in place. I got mine from rockauto.com. Its very similar - the only difference is how the two tubes are braced to the core, but that is no problem at all.
Out of curiosity I checked where the old core was leaking, and the leak was pretty obvious as you can see.
I just used two flat screwdrivers instead of this special tool.
The whole AC unit has to be removed to get access to the evaporator and heater core... The slight surface rust that showed up where the gaskets were, was removed as well of course...
The big hole on the left is where the blower motor is installed.
This is where the AC box usually is installed
You can see how much has be removed just to get to the evaporator and heater core...
I discovered the first issue at the hot water valve
The hoses around the time relay delay were leaking a little bit
For testing purposes I hung a spare master vacuum switch into the car - this solved the problem
The old fast idle diaphragm was leaking and brittle and was replaced with a better one...
The 1967 Cadillac Automatic Climate Control Vacuum Schematic from the shop manual -
1968 is almost identical BTW... Click on the image for a larger view!
Here is a video about the Master Switch that a gentleman posted on youtube