mystery vacume line

[54bobby]

guys, blower motor is on blowing through defrost. i know this is a vacume thing and i have 1 line in that area (fire wall) that is disconected and i don't see any possible connectors for it. i have not checked the bladder yet and my son recently had the lower dash panel dropped to replace the dimmer switch. could he have inadvertantly disconnected something? starting with this lost connection first. does anyone know where this line runs to? it's the blue line (i added the cap for the pics) that runs through the black conduit.

 

can't get pic to upload???? wtf how do i upload pic? tried bbcode, flikr, copy and paste, nothing works.

[HOrnbrod]

http://comancheclub.com/topic/37727-how-to-post-pictures/

[54bobby]

i keep getting an error saying i'm not allowed to use that image extension in this community. i'm using flikr.??????????

[HOrnbrod]

You need to use a standard graphics extension like .jpg, .bmp, .gif, etc.

[54bobby]

[54bobby]

[Keyav8r]

The black and the pink (purple) vacuum lines that go through the fire wall just above the AC expansion valve are the lines associated with HVAC. Trace these two in the engine bay and make sure they are connected. One of them (can't remember which and to comfortable to go look) goes to the valve on the heater lines and I believe the other goes to a vacuum source.

That blue line has a check valve installed. Pull the cap off and see if there is vacuum when the engine's running. Maybe for cruise control?

[ParadiseMJ]

The white, blue, yellow, red are bundled for the vacuum lines for the front axle/transfer case.  On the blue line, there is a check valve (the little UFO looking thing), that one should not have a cap on it as Keyav8r says..  These lines have nothing to do with HVAC or cruise.

 

But as Keyav8r says, the pink and black wires coming out of the firewall have everything to do with HVAC and cruise.  Look at the black line and follow it under the battery tray, all the way to the vacuum reservoir behind the bumper (P) side.  A common area for a break or rub or being eaten by battery acid.  Bulk vacuum line is cheap, and cheap insurance to keep things working right. 

 

You also may be right that you upset something behind the dash.  There is a plastic vacuum "manifold" behind the heater controls that can come loose if it gets bumped or pulled on...it's where the other end of the pink and black lines going through the firewall end up  The lines on the passenger side are all for running accessories...cruise, HVAC, t-case, CAD, heater. They really don't affect on the running or driveability of the Jeep.  So it can have a vacuum leak and run fine.

[54bobby]

The white, blue, yellow, red are bundled for the vacuum lines for the front axle/transfer case.  On the blue line, there is a check valve (the little UFO looking thing), that one should not have a cap on it as Keyav8r says..  These lines have nothing to do with HVAC or cruise.

 

But as Keyav8r says, the pink and black wires coming out of the firewall have everything to do with HVAC and cruise.  Look at the black line and follow it under the battery tray, all the way to the vacuum reservoir behind the bumper (P) side.  A common area for a break or rub or being eaten by battery acid.  Bulk vacuum line is cheap, and cheap insurance to keep things working right. 

 

You also may be right that you upset something behind the dash.  There is a plastic vacuum "manifold" behind the heater controls that can come loose if it gets bumped or pulled on...it's where the other end of the pink and black lines going through the firewall end up  The lines on the passenger side are all for running accessories...cruise, HVAC, t-case, CAD, heater. They really don't affect on the running or driveability of the Jeep.  So it can have a vacuum leak and run fine.

ok cool, but if the line in question is for the TC, where should it connect? i see no place within reach of the line to hook it up to. 

[ParadiseMJ]

It connects on the other end.  It is a vent line.  If you look straight down along/on the inner fender you'll find 4 steel lines and a little plastic plug/clip type connector.  Those lines connect to the four steel lines.  Then the steel lines follow the inner fender and come out by the front axle, turning back in to color coded lines (in a wire loom).  Then if you go back to the transfer case, there is a big plug on the driver's side of the case.  the four lines plug into that. 

 

Somewhere along the way (and I forget now since I eliminated the vacuum axle and swapped in a 94 t-case and removed all those lines) the vacuum lines plug into the 4wd actuator on the front axle.

 

So, just to be clear, that blue line is just a vent, not covered.  The thingy on the tip LOOKS like it should be connected, but no. It's a one way check valve so air goes one way in or out to the air.  Any vacuum line that has one of those on the end is just that.  A vacuum line with nothing on the end is just sucking air.

 

The Renix vacuum system goes like so:  The vacuum SOURCE is on the intake manifold.  It crosses over the engine along the firewall, along the passenger fender and dives under the battery tray to the vacuum reservoir.  The reservoir "saves up" vacuum (when you're off the pedal, going downhill etc.) for when it's not being created (aka when you're accelerating, going up a hill etc).  That way you have vacuum to run your HVAC and cruise, consistently. 

 

So that's the fat line.  The skinny line FROM the vacuum reservoir connects to your Acessories (cruise, heater valve, blend doors) Just the one black line supplies vacuum to the plastic "vacuum manifold" behind your heater controls in the dash.  NO vacuum and all the blend doors default to DEFROST.  So just a small leak, a crack, a break, a rub, will sap your vacuum...and it might work some of the time.  A completely disconnected or broken line, non of that stuff will work, especially when you are accelerating.  Make sense??

 

Now, that is the passenger side vacuum system.  The engine side vacuum has almost ZERO to do with the HVAC side other than the intake manifold SOURCE line.  The ENGINE side vacuum is borne in the intake/airbox and throttle body.  A disconnected/broken line there will affect your fuel pressure regulator, CCV system, EGR, MAP and your Jeep will run like crap, if at all sometimes. 

[54bobby]

It connects on the other end.  It is a vent line.  If you look straight down along/on the inner fender you'll find 4 steel lines and a little plastic plug/clip type connector.  Those lines connect to the four steel lines.  Then the steel lines follow the inner fender and come out by the front axle, turning back in to color coded lines (in a wire loom).  Then if you go back to the transfer case, there is a big plug on the driver's side of the case.  the four lines plug into that. 

 

Somewhere along the way (and I forget now since I eliminated the vacuum axle and swapped in a 94 t-case and removed all those lines) the vacuum lines plug into the 4wd actuator on the front axle.

 

So, just to be clear, that blue line is just a vent, not covered.  The thingy on the tip LOOKS like it should be connected, but no. It's a one way check valve so air goes one way in or out to the air.  Any vacuum line that has one of those on the end is just that.  A vacuum line with nothing on the end is just sucking air.

 

The Renix vacuum system goes like so:  The vacuum SOURCE is on the intake manifold.  It crosses over the engine along the firewall, along the passenger fender and dives under the battery tray to the vacuum reservoir.  The reservoir "saves up" vacuum (when you're off the pedal, going downhill etc.) for when it's not being created (aka when you're accelerating, going up a hill etc).  That way you have vacuum to run your HVAC and cruise, consistently. 

 

So that's the fat line.  The skinny line FROM the vacuum reservoir connects to your Acessories (cruise, heater valve, blend doors) Just the one black line supplies vacuum to the plastic "vacuum manifold" behind your heater controls in the dash.  NO vacuum and all the blend doors default to DEFROST.  So just a small leak, a crack, a break, a rub, will sap your vacuum...and it might work some of the time.  A completely disconnected or broken line, non of that stuff will work, especially when you are accelerating.  Make sense??

 

Now, that is the passenger side vacuum system.  The engine side vacuum has almost ZERO to do with the HVAC side other than the intake manifold SOURCE line.  The ENGINE side vacuum is borne in the intake/airbox and throttle body.  A disconnected/broken line there will affect your fuel pressure regulator, CCV system, EGR, MAP and your Jeep will run like crap, if at all sometimes. 

thank you, very informative response. that is what i was looking for.