I would see if you can rent a pressure tester. Pump the radiator up to about 15#s and use a flashlight to try to find the leak.
It could be as easy as a loose hose clamp...

Good idea. I got the dash out. Wasn’t that bad. As I began to take out the bolts it became apparent that someone has removed it before. Several screws missing was the tell tale sign. Now my that it’s out I’m sure I’ll find all sorts of goodies to fix. The accordion vent hoses all pretty mush disintegrated at the slightest movement. I’ll have to add those to the list.


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Late to answer with my shade tree figurin out but I used a shop vac on one hose in the core and my finger stuck in the other. It held vacuum so I knew it was good. Bought a new valve and replaced all the hoses now all is well. 

"I do run my heat from time to time just for a piece of mind."

Dang da lank lank dang dang...I'm a grinnin.

 

 

Edited January 11, 20223 yr by siteunseen

With the dash out, I really can’t see where the leak is coming from.   The more I take apart the more I fear I won’t be able to put in back because it could be weeks I before this dash goes back in.   I guess now is the time to get new bulbs and clean up the gauges. Is the general consensus to go LED so you don’t need night vision goggles to read the gauges.  
I have like 5 simultaneous projects going on at the same time on this car….. not by choice.  Anyone out there have a 77-78 volt/fuel guage laying around?  Minnie looks pretty rough, and the display for the volts is rusted.   

8 minutes ago, Av8ferg said:

Is the general consensus to go LED so you don’t need night vision goggles to read the gauges.  

Yes, go LED.  I'd also replace all the vacuum hoses while it's apart.  If you can swing the money, update everything to Speedhut gauges that actually work properly.  The Datsun speedo is always off and the tach was bouncy in every Z I've had .

35 minutes ago, Av8ferg said:

With the dash out, I really can’t see where the leak is coming from.   The more I take apart the more I fear I won’t be able to put in back because it could be weeks I before this dash goes back in.   I guess now is the time to get new bulbs and clean up the gauges. Is the general consensus to go LED so you don’t need night vision goggles to read the gauges.  
I have like 5 simultaneous projects going on at the same time on this car….. not by choice.  Anyone out there have a 77-78 volt/fuel guage laying around?  Minnie looks pretty rough, and the display for the volts is rusted.   

 

 

 

 

I may be the occasional helpful card catalog but the brainiacs are the authors of the books. I just ride their coattails. 

 

Cliff, once again you saved me a bunch of time.   I just ordered those bulbs  for the gauges.   So much work….so little time.  

My latest struggle…removing the the heater core OMG is this an PITA. Any words of wisdom? So far disassembly is a guessing game, just removing screws and trying to get access to this thing. I’m sure it won’t be easy to find a replacement either.
Here’s where I’m at!



The good news is my fuel tank restoration is complete. Should be here in a few days. Will report the how it came out for others needing this done once I get eyes on it.


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I took mine out about a month ago, I can snap some photos if you need any. But pretty much, remove all the screws 🙂 there were a couple screws holding it to the firewall (I believe on the driver side) that I missed for the longest time. I pulled the core and HVAC controls all together. You’re on the right path by removing the blower first. 

I used 1/4" drive sockets with the smallest open-end wrench I had to turn them. Took the seat out and laid some foam and a pillow over the door sill. I still ended up sore as ever for a few days. Pain meds helped me through it but your a pilot so no, no for you.

Are you replacing the valve and hoses or the whole thing? Your pictures shows a leaky valve for sure.

@jfa.series1 was a big help with all his photos. Good luck!

 

Cliff, everything is pretty much toast. Finally got the heater core out….it looks shot too. Now I have to find one and from the looks of it I won’t be a stock heater core. I saw the Captain Obvious used a alternative core from an Escort . I might have to do something like that. I’ll have to pick his brain. Pain….every time I cross one hurdle I get two more thrown at me.




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@Av8ferg I won’t be using any of my oem hvac system besides the control panel. I can send you some photos of what I have in hopes it can help. I’m not sure how operational it is since I never tried to use it and it sat for 20 years. Let me know 👍