Vacuum leak - the last straw!

[Skandocious]

First off-- hi everyone! Its been a while since I've been posting, I know... The Apple internship is keeping me CRAZY busy. Hope all is well with all of you. I saw that Tex left so at least SOME stuff is improving around here

Anywho-- I've been fighting a slight vac leak in my truck since I bought it... Everytime I would climb a hill or load the engine me vents in the cab would shut off and default to the defrost vents. Well it used to only happen on large hills so I kind of ignored it but recently it got much worse and now even if I hit a slight grade at RPMs lower than 2500 my vents shut off and it takes a while to build back enough vac to switch them back.

Has anyone found a particular problem spot that commonly leaks and causes this? I don't think it's a big leak in the engine compartment because I don't seem to be having any noticeable driveability issues. But hey maybe I am having some-- what's the trademark symptom of a bad vac leak?

Any help here would be great. I've done several general surveys on my vac lines and, although old and stiff, they all seemed to be intact.

 

[Truckin4life]

Vacation hose going into the cab was where my issue was. Passenger side above the heater.

 

[Skandocious]

The white one going to the vacuum solenoid on top of the blower box?

 

[5.0Flareside]

yeah, that is what controls the AC whether its blowing or not really.

 

[Truckin4life]

Ill have to look. But mine was cracked in the cab. Behind the passenger side kick panel.

 

[Skandocious]

I was fiddling with the vac solenoid on top of the blower box and I can't seem to figure out just what in the hell it does. It never actuated at all no matter which setting I had my blower knob on (yes the truck was running). I could see the one under the dash move when I switched the knob but the one in the engine compartment never budged. I also actuated it by hand and the direction of the air in the cab never changed... Anyone know what that vac solenoid actually does?

 

[Truckin4life]

Does it turn on the AC?

 

[Blue Goose]

I was fiddling with the vac solenoid on top of the blower box and I can't seem to figure out just what in the hell it does. It never actuated at all no matter which setting I had my blower knob on (yes the truck was running). I could see the one under the dash move when I switched the knob but the one in the engine compartment never budged. I also actuated it by hand and the direction of the air in the cab never changed... Anyone know what that vac solenoid actually does?

Outside air vs. recirculate???

 

[Skandocious]

How do you recirculate air in these trucks? The Max AC setting?

 

[Blue Goose]

Yes sir, that is the recirculate.

 

[dustybumpers]

check the vacum reserve can [coffee can on pass fender well], mine had pin holes rusted in the bottom, and it made the a/c act just like that. full throttle, vent would go right to defrost

 

[Skandocious]

Full throttle I'm actually mostly okay. It mostly happens when the engine is loaded like low RPMs going up a hill.

And I don't have a coffee can-- I believe mine is made or plastic. If that's the case then it couldn't be rusted.

 

[Truckin4life]

Plastic covered???? Check the line inside the cab. It fixed my issue.

 

[Skandocious]

Not plastic "covered"-- it's an entirely different looking container. You can see it in this picture:

 

[dustybumpers]

cool, never knew they went with plastic. that will be what I get next time. thanks for the picture

 

[dustybumpers]

it's not your issue for thse vacum problem, but I see your filter is off the hose that goes to your air pump

 

[95F350XL]

We have a smoke machine at work and we hook it up to the vac lines and smoke comes out where the leak is at.

 

[Skandocious]

Ooo that would be nice. Wanna bring it to Cali?

 

[blacksnapon]

Get a vacuum pump, then put a vacuum on the reservoir when isolated. That will eliminate the "can". Then trace your vacuum lines to where they go into the cab. There will probably be a place where it tees off before the firewall. Plug off that tee. Go to the back of the HVAC control. Find the main "feed" at the control head (the vacuum connection). Plug that off, then apply vacuum at the connection by the reservoir. That will verify the lines integrity. All that's left is the control head.