Vacuum problems

[phenopd]

My problem is with my '03 7.3. I figured this was a good place to post this, there's a lot of experience here.
My switch for changing from defrost to vent to floor etc. has defaulted to defrost only. I know my vacuum pump is good as I've tested it and there seems to be good vacuum. No problem with the brake booster,
brakes work fine. The only symptom seems to be no vacuum at the switch controlling the distribution from defrost to vent etc.
does anyone have any experience with tracking down a gremlin such as this? I tried smoke to reveal the leak source but there seems to be a valve that stops any positive pressure getting through. Any experience with this?

 

[Raul]

Vacuum tank check valve or cracked tank. The valve is $10. Replacing it can be $1000 as you have to remove a lot of heating and A/C stuff. Options:
A) take it to the dealer
B) reach the valve by cutting a window on the front passenger side fender and replace the valve
C) disconnect the vacuum line before it goes to the tank, locate the line that comes from the tank at thepassenger foot footwell and place a new valve and tank hiding in your dash board.

I did B to replace the valve and two years later had to do C as the tank leaked.

If you do a search on google you'll find a lot of post with pictures about this. It is van related, not just the 7.3

 

[Vannibal Smith]

Choice c is really simple...bypass the original vacuum reservoir by cutting the old line where it comes out of the engine...then run a new line from the engine, through th the dog house and into the passenger foot area...mount up a new reservoir and said live back into the vacuum lines coming into the footwell from the engine compartment...it's easier than it sounds...tons of YouTube videos


Sent from my iPhone using Tapatalk

 

[VOODOO7.3]

Here is a link to a thread where I described how to fix your problem:
http://www.sportsmobileforum.com/forums/f33/vacuum-leak-in-vents-17921.html

 

[VOODOO7.3]

By the way, you don't need the vacuum reservoir tank on a diesel. All Ford vans have them because the vast majority are gas engines. For gas engines, the reservoir provides instant vacuum upon startup before the engine develops enough vacuum. The OP has a 7.3 diesel, with a vacuum pump, and can bypass the hard to access cannister altogether. On a gas van, you would have to cut a 3" x 5" access hole at 12 o'clock above front right tire through inner fender metal. Don't run your new vacuum hose through the doghouse. Run it through the hole where the existing one goes through above passengers feet. That's where the diverter flap is located that defaults to defrost without enough vacuum pressure. You can buy 10' of same diameter silicone hose (pinkish/salmon color) in plumbing aisle at Home Depot for about $10. Won't have to mess with it again.

 

[phenopd]

Well I knew I would find some answers here. I'll give "c" go and check back.
Thanks guys, Mike

 

[phenopd]

Well I've been pretty busy, but I removed the grommet to find that behind it was connected to a "t" that was still intact. I haven't had a chance to get back to it yet. I'm thinking that I'll try to sever the part of the tee that looks like it goes to the canister, then I should be able to pull the other tube through, connect my new piece to it and fish it back to hook it back up under the hood.
Anyway that's the plan. Maybe I'll get to it mañana.
Mike

 

[VOODOO7.3]

If you want to fix it one time and move on with life, you can simply run a new 10' silicone hose in place of the existing one. I posted a link to all of the info above. Bypass the cannister by snaking the new hose from inside the cabin to inside passenger fender then to where existing hose connects to vacuum splitter near oil fill cap. It can all be done in about 20-30 minutes.

 

[phenopd]

Voodoo: yeah, I followed your instructions in your post that you referenced, was pretty easy. The rubber hose was rotten. When I tested it I still had no air out of the dash. I have floor , defrost, but none from the dash. Do you know which vacuum switch it is? I'm thinking it must be bad. The vacuum at the manifold is almost 24 inches mercury and I have vacuum to my new hose.
What else could it be?

 

[VOODOO7.3]

OK, good! Glad you now have vacuum to the controls! Make sure the flapper is moving freely inside the diverter, with no crud or blockage. Diverter is black plastic box going through firewall at passenger footwell. There have been some cases where either wrappers, leaves, or the factory foam separates and blocks flap operation. I've been working crazy long hours but I'll dig around and see if I can find any helpful info. I'm thinking it is unlikely for the electronic climate control switch to go bad at same time as a vacuum problem, so I would check condition and placement of other vacuum hoses connected to the switch under center dash access panel. You could take a photo first of what hoses are connected to which ports, and then try switching some applying your new main hose to other functions. Possibly isolate the problem. I just hate throwing new parts at a problem before finding it! I'll try to find you a vacuum diagram for that if I can. In the mean time, maybe someone else will chime in with knowledge on what causes no center vents. Way to stick with it though, you're almost there!

 

[phenopd]

To close the loop , I got vacuum to the control, (thank you voodoo 7.3)but still no air from the vents. Frustrating. I finally removed the trim around the switch ,opened the access panel on the dashboard and started testing. If you have a tube that fits you can create your own vacuum with your mouth to test the vacuum solenoids. Well, I found the one that controls the selection of where the air goes and isolating it,it worked perfectly. I played with the arm connected to it tested it again and it works!! Yay!!
I guess persistence works.
Mike