1980 toyota pickup, 1983 22r engine

My question is, What is the minimum psi present in the cooling system of a running 22r engine?

i ask because i am going to attempt to swap out all of my heater/defroster/fan cable operated controls for electric solenoid switch operated units. The retro fit will include two normally closed water valves that open when energized but require a minimum of 3 psi in order to operate. 3 position switch would either open the heater core-high heat, open bypass-no heat, or open both heater core and bypass-for a low heat "blend" option.

i know the maximum psi would be limited by the radiator cap (13psi) but i cant find a straight answer on what the lowest pressure would be. If it helps i run a 2 stage oem toyota 180 deg t-stat. solenoid valves will be installed in the same firewall location as the stock set up.

 

The lowest pressure would be 0 psi. Duh When the engine is cold non of your solenoids will operate. But when its warmed up is above 3psi. Don't know what it is eggsactly but its above 3psi.

 

No, No, No.

The cooling system pressure is irrelevent, because whether it's 5 pounds or 150 pounds, it exists on both sides of the valve, making the effective pressure zero.
The pressure that is needed to enable the valve to open has to be provided by water pump pressure that is creating flow thru the hose. I don't know what pressures are created by the water pump impeller, but I don't imagine that the pressures can be too high. Might be enough to permit your solenoid valves to function, or it might not.

 

My word choice was poor, the pressure i need to know is that which is provided by the water pump at idle rpm. I have found numerous equations which would get me in the ballpark if i could provide that information, I got the valves at a low price, if they fail, its no different than a regular heater valve stuck shut so im not too worried, if it works like a charm, ill post up my slick custom climate controls in a thread and share. Thanks Mill, helped me unclutter my though process a bit, and you are correct on all points.

 

I think your over thinking this a little. Do you already have these valves that your going to use? If so, wouldn't it be easier just to test one on the truck? Also you can use a pressure gauge on the system with the truck running to find out what psi it has. I honestly don't think anybody knows what the pressure is because nobody has ever needed to know.

 

Except when the valves to the heater core are closed, then their would be pressure only on one side of the valve, since the water in the heater core would cool and lose pressure.
In theory.

 

As far as I know, there is a valve only on one side of the heater core, leaving the other side of the loop open to the entire cooling system and therefore, free to equalise pressure at all times.

 

Ya thats true. I guess it would be the same everywhere in the system. Except on the other side of the thermostat of course.

I still think its as simple as hookin one of the valves up and testing it.

 

Sub'd for the custom controls!

 

Valves arrived today, my trucks interior is getting made over so i have no seats and no shifters or shifter holes in the new vinyl floor yet, i did bolt the gas pedal back on, so weather permitting tomorrow, before i pull my old dash ill jerry rig a switch to one of these valves and give it a shot, the sweet customness is a ways off. Im still working on how to fab a blank dash bezel, im not too keen on hacking up an uncut original (how i wound up with two uncut bezels is beyond me)