How much vacuum in/Hg is needed to pull up the hot water valve

[92nsx]

I am wondering how much vacuum in/Hg is need to pull up the hot water valve so coolant flows thru the heater core. Mine will not pull up even after bypassing the VSV. Right now I have around 12-14 in/Hg on idle with my 272's. I know it is lower than OEM but is it too low not to open the valve? I can manually open it as well as "suck" it open when I use me as the vacuum pimp. (yes I tried to word it so it doesn’t sound sick the best I can).

Does anyone know where in online tsrm this is located at?

Pic bowered form SOGI

 

[JesseH]

Even though your valve works fine your switch might be bad, it's what lets the vacuum get to the valve.

Try doing this to see if it works just to check, all your doing is bypassing the switch so you always get vac to the valve.

EDIT: sorry I just realized you said you already tried bypassing.

 

[92nsx]

Bump

 

[Piratetip]

I tested this awhile back and from what I remember it didn't take much to start to open it.
10 in/Hg or so. I would go test it for you, but mine is in storage.

 

[jetjock]

Just for you I went out and measured it. The rod starts to move at 10 and once all the free travel is taken up needs 14 to begin lifting the lever. It takes 18 to fully open the valve.

 

[92nsx]

^^^ Cool, thanks JJ. You the man, that was exactly what I was looking for! :drink1:

 

[jetjock]

If you don't want to remove the valve just suck it open and permanently pinch the hose

F=P x A. If you can't increase delta p you can increase area. That means a bigger diaphragm. Or wire in the little vacuum pump from a GTE's cruise control. Maybe not as easy as yanking the valve off but at least you won't be making the car a bigger POS than it already was...something many owners seem to be very talented at.

 

[strippedsup87]

dang that is just crazy....Why did they make it so much to open the valve?

 

[92nsx]

Valve is still in and working fine now JJ Just needed a little TLC, cleaning, and to find a vacuum line off under the CC. Also I seem to be getting better vacuum inHg now since there is a little over 600 miles on the engine now. Idle is around 15 inHg and crusing down the free way around 28-2900 RPM's it is 18-19 inHg.