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Op..i drove my car many times like derek says..below freezing dead cold.. i removed mine or you can plug or wire open. I have no issues other than longer high idle for a minute or two when cold.
i would not waste your time trying to fix this. It can harm your engine.
i would also put in a 180f thermostat for a street car. I have no idea at what that valve opens but would think below 160f. Edit see earlier 180f is opening
often low temperature or no thermostat is just hiding cooling issues.
you could also post many pics of your hoses and valves, someone may have misrouted too..
zero reasons to leave that valve operational imo.
Last edited by interpon; Feb 26, 2022 at 02:36 PM.
So at this point you know your actuator is working.
You still have not isolated the problem.
The original EFE TVS switch 1975-1980 used the same. It is stamped 180 on the bottom.
IS your cooling system actually rising above 180+?
If so test the EFE TVS switch
Drain some coolant out of your radiator, just below the upper hose level.
Pull the EFE TVS switch.
Plug the top port with a rubber nipple.
Pull a vacuum on the second port, anything over 6 inches of vacuum is enough.
Make sure it holds a vacuum.
Heat water up in a coffee cup I used the microwave, about 1 minute 45 seconds.
Insert a meat thermometer, water should be above 200*.
Still holding a vacuum, Insert EFE TVS switch just to the threads.
Your switch should change state (exhaust) +- 30 seconds or so, if not replace switch.
Notice, just under 200* on my original EFE TVS switch is when it actually exhausted.
New replacement switch: Standard Motor Products PVS43
ok so I started the car cold . Heat riser moved to close position as it should .. when the car warmed up it did not return to the open position which is the left side… I proceeded to takeoff the vacuum hose connected to the actuator and then the heat riser went back to the left and opened… just double checking before I buy the parts that would be a bad TVS switch correct .. I am sorry to bother anyone I am just learning about the 75 year car
If you feel like throwing money at a solution, buy the Mity-Vac that I linked in another thread. You can see one being used in @bmotojoe's post above. Until you do that experiment, or part of it, you don't know if the "problem" is the TVS, your thermostat, vacuum routing, or something else.
While the heat riser does very little good for you, having it closed can be a huge problem. You will lose power, and a hot intake can cause vapor lock in your carb. In the meantime, please remove the vacuum hose and plug it. Or trace it back to the source and plug it there. Below is an older photo of my 79 (the wires were instrumentation for a temperature experiment). The vacuum hoses have been removed from the TVS and EFE valve. Though much cleaner now with a new water neck and 180 deg thermostat, my car has run for 5 years with an always-open heat riser.
