Vacuum leak.

[95bajaguy]

I have traced my a/c vacuum leak to the 2 hoses that go into the firewall on the passenger side. Does anybody know how i can gain access to those? I need to replace both. Do i need to pull my plastic fender out?

 

[Mark_88]

I have traced my a/c vacuum leak to the 2 hoses that go into the firewall on the passenger side. Does anybody know how i can gain access to those? I need to replace both. Do i need to pull my plastic fender out?

Hello and welcome to TRS~!

Do you mean the vacuum lines that control the blend door and other HVAC or something else?

The vac lines on my 96 fed through under the box (there was only one I think) but come out of the check valve (round ball) that is connected to manifold vacuum. They can be accessed without removing the fender liner but it may require crawling under the truck...jack it up or use ramps if you have them...and are comfortable with that.

I've used ramps a few times and they are actually much better for some things than jacking up the vehicle...and a good set of ramps can be rented if you have a rental place in town.

 

[95bajaguy]

Hello and welcome to TRS~!

Do you mean the vacuum lines that control the blend door and other HVAC or something else?

The vac lines on my 96 fed through under the box (there was only one I think) but come out of the check valve (round ball) that is connected to manifold vacuum. They can be accessed without removing the fender liner but it may require crawling under the truck...jack it up or use ramps if you have them...and are comfortable with that.

I've used ramps a few times and they are actually much better for some things than jacking up the vehicle...and a good set of ramps can be rented if you have a rental place in town.

No there is one that goes from the check valve closest to the front and there is one that goes from the valve on the heater core. They both go into the firewall. You can trace them to under the blower motor and heater core under the hood. And if you get inside the truck on the passenger side there is a connecter with a black and white vacuum line near the floor (they control the vents and max a/c). Thats where they meet. I need to replace the 2 on the engine side.

 

[RonD]

The hard plastic hose is cheaper than the rubber hose which is why car makers use it, there is no "better" between plastic or rubber hose in this application, just a matter of cost.
There should be a Black line to check valve and Gray line to heat control.

You should be able to see them between inner fender and Blower/evaporator housing

You can get correct diameter rubber hose that fits snugly over the hard plastic line to do repairs, or to replace whole lengths and route it as you see fit.
No clamps are needed since this is a vacuum system, it tends to pull the connections together vs push them apart like a heater hose connection for example.
But up to you, simple zapstrap/wire tie will be fine


Usually you can cut the hard line and leave a few inches sticking out at the firewall and replace the middle part to check valve, and/or Heat control valve, with rubber hose

Wrecking yard will be the only place that will have the whole lengths of the hard plastic lines, and they are often damaged so check carefully.

 

[Mark_88]

OK...someone posted a link while ago to a supplier/manufacturer of the smaller plastic hose...but it was quite a while ago...but within the last year...might be hard to find it again.

This question comes up now and then so it is a fairly common issue...as RonD said the junkyard would be a good place to start looking if you can't find it anywhere else new...I've stripped older vehicles of this stuff when I had my 88 2.0 that was a nightmare of vacuum lines...but did find quite a few places where it got too close to the exhaust or something else that was hot...so inspect it if you use junkyard stuff...easy enough to miss a small hole in it.

 

[little red ranger]

the vacuum causes the blend door to move,,, no vacuum then you get defrost,,, or if blend door hing is bad and door is shut you only get defrost

 

[RonD]

the vacuum causes the blend door to move,,, no vacuum then you get defrost,,, or if blend door hing is bad and door is shut you only get defrost

Blend door uses an electric motor, it is also only used for temperature settings, it regulates air flow thru the heater core.

Vents do use vacuum motors, and yes, Defrost vent setting is default setting, so OFF or if no vacuum is present to run the motors = Defrost Vent

Image here of the vent setup: http://www.ford-trucks.com/forums/attachment.php?attachmentid=517&stc=1

Blend door uses an Actuator, an electric motor, and is a temp door
Defrost/Dash door use a vacuum motor
Floor/dash door uses a vacuum motor
Fresh/recirculate air door uses a vacuum motor

 

[ratdude747]

On my 1995 there are two vacuum lines linking the cab to the engine compartment. The black one goes to the Vacuum canister and supplies the HVAC vent system (not the blend door, the vent controls). The gray line is used to control the heater valve, which comes from the vent switch. Good thing I happened to be swapping evaporators yesterday, hence why I remember all of this.

You don't want to cut either line if you can help it.

Leak points would be the connection at the bottom of the evaporator box, the vent switch in the center of the dash, the connection to the heater valve (on the heater hoses in the engine compartment), and vacuum solenoids in the HVAC system, especially the one right by the bottom of the heater/evaporator box (they can get kicked loose by passengers). I had the latter happen on a Dodge Durango (only in that case it was on the driver's side), drove me nuts why my vent control quit working. Whoops!

 

[95bajaguy]

It's fixed, I replaced both lines. Now I could use some help with my other problem if yall know anything about it. I'm getting close to torching the truck. Thanks. http://www.therangerstation.com/forums/showthread.php?t=168639