I believe the 4-button systems are the only ones with the firewall-mounted (electronic) vacuum switch, but I could be wrong....I think you get either the transfer case (mechanical) vacuum switch or the electronic switch, but not both.

 

yea but i plugged the main manifold line before the check valve so there should be no other vacuum's right?
i still hear noise (sounds like its coming from where the hvac controls are or lower under it)
almost like if it was the radio not tuned to any station (static) but a very quiet volume
could be a hissing but more like static noise or something
kind of confused as there is no vacuum connected as i have it all plugged

 

If you unpluged the check valve from the engine side of the valve, depending on where the leak is, there could still be vacuum in the system, (if it only leaks in 4WD). If you totaly remove the check valve, all vacuum will vent to atmosphere. Can't explain the noise, unless you're hearing coolant flowing through the heater core.

 

try with your brake booster vac hose removed... (be sure to cap it) it might be your brake booster leaking... not likely but possible

 

i burped the radiator by putting it on car ramps and letting it idle at 3000rpm wth radiator cap off and made sure i see thermostat was open by looking in the radiator hole and make sure i see plenty of circulation (which i did)
i let it run like that for at least 15mins

still makes the same noise


so i then pulled the vacuum hose off the brake booster and i sealed the hose and started the car and it still makes the noise


i cant figure it out
after i turn the engine to off (with key) i can hear the sound get slower then stops which takes about 1-2 seconds at the most for it to completely stop making noise.
so that does make me think its a vacuum leak but i sure dont see how it could be if i have manifold line plugged before the check valve and also have the brake booster vacuum line plugged to.

i cant hear the noise if i roll down my windows or if i step out of the car because the muffler on the car is loud and engine noise to.

what could it be do you think?
maybe i should plug the manifold and brake booster sources before the vacuum line and at the actual ports but i dont see how that would help because it sounds like the noise is behind the dash somewhere but towards the center and lower area

not sure what to do.

 

The way you describe the noise, I'll bet it's vacuum. Sounds like it's still connected and you're hearing the vacuum leak until it's vented. Are you sure you have the vacuum line disconnected? Try totaly removing the check valve and see if the noise is still there. This image might help:

 

just to be sure... is your blower on? heater set to "off"?

 

with manifold line plugged (before check valve)
check valve = just hanging in the air
when heater = off
i switch blower to on or off dont seem to do anything


in the picture you kindly provided above mine is vacuum lined like that one
i also have the check valve disconnected (hanging in the air)
i then plug the manifold line (and also unplug it) and i keep getting same noise inside the car around the middle to lower dash area

check this out
even with the vacuum line plugged before the check valve
i can switch the 2hi to 4hi to 4lo (while in nuetral) and all the lights work correctly....flash for a second while it switches and then goes steady on
i hear the noises under the car and also the noise in the passenger kick panel

so when the manifold vacuum line is disconnected why am i not getting constant flashing lights for 4hi or 4lo
it should only stay in 2hi shouldnt it?
thanks for any info and if you have anything else you want me to do let me know

1 more note i have a vacuum guage (no pump) and i hooked it to the manifold line and it showed a constant 18PSI pull.

 

Disconnecting the manifold side of the check valve still leaves vacuum in the HVAC & 4WD systems: the lines, actuators in the dash, and the vacuum reservoir. That's what the check valve is supposed to do. The reservoir stores enough vacuum to operate either system a few times before it is depleted.

No flashing 4WD drive lights, and the system actually shifting into 4WD, means the actuator is getting vacuum and pulling the cable. You're hearing the noise in the dash for a few seconds after you shut the engine off. Both of these things pretty much confirm the above statement, (still has vacuum in the reservoir). Completely remove the check valve, check for the noise in the dash, and try the 4WD. The transfer case will shift, but the axle actuator will not engage the right front axle. The 4WD light might flash and the system will remain in 2WD.

 

yea but the problem is the 4wd rf actuator is not engaging

when i jack the wheel up and put it in 4hi or 4lo i can still spin the wheel but it is clicking
so someone said it might be that i dont have enough vacuum to engage it all the way or something along those lines so i was looking for a leak by disconnecting systems but from what you say (the res is holding and not leaking)

i will go out in a minute and completely disconnect the check valve and test the 2hi, 4hi and 4lo with the manifold line plugged and unplugged and while im doing that i will also listen to see if the sounds is still there.

its raining right now so it might be a few mins

completely disconnected the check valve and left manifold line open (sucking air)
still hear the noise
2hi, 4hi and 4lo buttons appear to work like they are supposed to
they flash for a split second when i pretty a new button then i hear the noise then i see lights go solid

dont know how this can be as the vacuum lines are disconnected