(09-22-2026, 03:03 PM)whited44 Wrote: That does make sense. Of course valve 2 is seized up.. I tried to close it with no luck. If 3 and 4 are the inlets then if I can get those closed it would help with my heater core leak yes?? Or does the return side also need closed??
Correct if you close both of the supply valves that should stop the flow in the loop and hopefully would stop your leak.
If the return loop is left open, the heater core will be exposed to the system pressure, somewhere between 12 and 16 psi depending upon the radiator cap.
Richard and Rhonda Entrekin
95 Newell, 390 Ex caretaker
99 Newell, 512 Ex caretaker
07 Prevost Marathon, 1025
Maverick Hybrid Toad
Inverness, FL (when we're home )
(09-24-2026, 04:13 PM)Richard Wrote: If the return loop is left open, the heater core will be exposed to the system pressure, somewhere between 12 and 16 psi depending upon the radiator cap.
Yea, true I was not thinking as much about the pressure as much as flow. Not to mention you would be losing the pressure in the system from the leak, which is not good for cooling system performance.
Dennis you may try loosening the packing nut on the valve that will not move. Sometimes if you loosen that it will allow you to turn the valve. Just make sure you tighten it back or it will leak. The packing nut is the nut that is on the stem of the valve.
(09-24-2026, 04:13 PM)Richard Wrote: If the return loop is left open, the heater core will be exposed to the system pressure, somewhere between 12 and 16 psi depending upon the radiator cap.
Yea, true I was not thinking as much about the pressure as much as flow. Not to mention you would be losing the pressure in the system from the leak, which is not good for cooling system performance.
Dennis you may try loosening the packing nut on the valve that will not move. Sometimes if you loosen that it will allow you to turn the valve. Just make sure you tighten it back or it will leak. The packing nut is the nut that is on the stem of the valve.
I heaved on these valves pretty hard. I have a plumber buddy coming over this weekend and we’re replacing all 4 and putting ball valves in it. Draining all the antifreeze Saturday, doing the valves Sunday.
Still doesn't really help with what valve goes to what though unfortunately
If you have the 4 hoses disconnected you can use air to figure out the pairs, on 712 it was easy to figure out what houses were engine heat the aqua hot returns went to a common manifold, if you pinch one of the engine heat hoses off at the aqua hot you will know what 2 hoses are for aqua hot, also 712 does not use engine anti freeze for the aqua hot so the liquids are different colours
The only difference is that with your era AH, the engine coolant IS the coolant inside the AH. That era AH has the potable hot water loop wrapped on the outside of the AH boiler.
AH changed the design in the early 2000s to put the potable hot water loop inside the boiler which necessitated a change to propylene glycol as the AH fluid. The internal loop could crack and contaminate the hot water. If ethylene glycol (engine coolant) were used in the latter unit, it could poison the potable hot water. Propylene glycol is not toxic to humans.
Richard and Rhonda Entrekin
95 Newell, 390 Ex caretaker
99 Newell, 512 Ex caretaker
07 Prevost Marathon, 1025
Maverick Hybrid Toad
Inverness, FL (when we're home )
Well my valves got delayed from Amazon. My plumber can’t change them till later. I have a trip coming up and by passed the heater core for now. Here are some pics. Decent access after removing the top dash panel
(10-03-2026, 02:25 PM)whited44 Wrote: Well my valves got delayed from Amazon. My plumber can’t change them till later. I have a trip coming up and by passed the heater core for now. Here are some pics. Decent access after removing the top dash panel
Nice work Dennis. Tell us more about the top dash panel you removed? I looked all around mine and did not see a way that the dash would come apart. Maybe they are different but I would love to see more pics of how you accessed it.
(10-03-2026, 02:25 PM)whited44 Wrote: Well my valves got delayed from Amazon. My plumber can’t change them till later. I have a trip coming up and by passed the heater core for now. Here are some pics. Decent access after removing the top dash panel
Nice work Dennis. Tell us more about the top dash panel you removed? I looked all around mine and did not see a way that the dash would come apart. Maybe they are different but I would love to see more pics of how you accessed it.
Here are some pictures. The top piece snaps in place
Good access to the gauges. There is a wet spot on the floor right by the fuse panel under the glove box. I’m hoping it’s just residual antifreeze. Nothing under the dash appears to be wet but who knows
(10-03-2026, 02:25 PM)whited44 Wrote: Well my valves got delayed from Amazon. My plumber can’t change them till later. I have a trip coming up and by passed the heater core for now. Here are some pics. Decent access after removing the top dash panel
Nice work Dennis. Tell us more about the top dash panel you removed? I looked all around mine and did not see a way that the dash would come apart. Maybe they are different but I would love to see more pics of how you accessed it.
Here are some pictures. The top piece snaps in place
Good access to the gauges. There is a wet spot on the floor right by the fuse panel under the glove box. I’m hoping it’s just residual antifreeze. Nothing under the dash appears to be wet but who knows
Nice, thanks. So you just pry gently up on it and it comes off? Are they using those Christmas tree type fasteners to hold it down?
Yea hopefully, I have a slight leak I believe in my windshield. I can see where they tried to fix it with silicone all along the top of the windshield gasket.
)
