Vacuum Leak? hissing from dash

[jakeyf08]

Today replaced the vacuum hoses under the hood that run from the canister to the intake manifold and the other two. Now that i have replaced these I noticed a hissing coming from somewhere under the dash. it sounds like a hose is leaking somewhere in there now???? I am not positive where the hose goes that runs through the fire wall and how I can find the problem? should i drop the entire dash and check it out? or is there a much easier way to fix this...thanks in advance any help is greatly appreciated.

[MT-2500]

Originally Posted by jakeyf08

Today replaced the vacuum hoses under the hood that run from the canister to the intake manifold and the other two. Now that i have replaced these I noticed a hissing coming from somewhere under the dash. it sounds like a hose is leaking somewhere in there now???? I am not positive where the hose goes that runs through the fire wall and how I can find the problem? should i drop the entire dash and check it out? or is there a much easier way to fix this...thanks in advance any help is greatly appreciated.

Do not rip out the dash yet.
Stick your head and ears and eyes under dash and have a look and see and listen.
Try to hear where the leak is and look for hose off or broken.

POST BACK WHAT YOU FIND UNDER THERE.

[jakeyf08]

I took a look and I found out it is coming from behind the air/heat controls. I pulled out my ash tray and looked around up there but couldn't really see anything. I also notice that when I turn my a/c it cuts out while accelerating and then kicks back in when cruising. I hope that helps diagnose the issue. I could pull off the controls and look behind it if there is a possibility that a line runs through there?? Again, any help is appreciated.

[MT-2500]

Yes.
Pull ac /heater control and see if the leak is there or other place.

[jakeyf08]

I pulled the ac/heater control and it is coming from even further behind that. I couldnt really feel any lines behind there since there is a large cluster of wires running through the only open hole behind this part of the dash...i did notice on the control that allows you to select ac/heat/defrost and so on that one of the holes is missing a wire running to it...is this normal?

[MT-2500]

Originally Posted by jakeyf08

I pulled the ac/heater control and it is coming from even further behind that. I couldnt really feel any lines behind there since there is a large cluster of wires running through the only open hole behind this part of the dash...i did notice on the control that allows you to select ac/heat/defrost and so on that one of the holes is missing a wire running to it...is this normal?

Not sure what you got but no wires should be going threw vacuum ports.

You need to get on in there and find that leak.
Good luck

[jakeyf08]

I have yet to find the source of the leak. I notice that when I start the vehicle you can hear the noise, then when u turn the max ac or ac on the noise continues but when i turn the control to the floor and top vent setting the noise stops. I hope this can help diagnose the problem.

[MT-2500]

Originally Posted by jakeyf08

I have yet to find the source of the leak. I notice that when I start the vehicle you can hear the noise, then when u turn the max ac or ac on the noise continues but when i turn the control to the floor and top vent setting the noise stops. I hope this can help diagnose the problem.

You are going to have to look and listen for the leak.
Check the vacuum lines to ac/heater housing and the vacuum pots on it.
Pot is leaking or hose off or bad.

What year make and model and engine is it?