Vacuum to Chassis

[Maxium]

When you look at the underside of your hood, you see at sticker that shows the routing of the vacuum lines. One line goes to "Chassis". Does anyone know where this vacuum line goes to? Does it just terminate there or does it hook into some other component? Thanks guys.

 

[trinity_gt]

I'm going to venture that the "chassis" is referring to a feed to the HVAC system door control motor/acuators which run on engine vacuum.

 

[Maxium]

I see, so the vacuum would then feed the module that controls vent positions?

 

[trinity_gt]

The door positions in the HVAC box are controlled by "vacuum motors" and those, in turn, are controlled by the dash switchgear. They are motivated by engine vacuum...

 

[Maxium]

If that's the case, do you know if there are more vacuum lines behind the firewall or does that chassis line directly plug into the HVAC module? Reason being is that I'm trying to check all my vacuum lines for cracks and such.

 

[trinity_gt]

If that's the case, do you know if there are more vacuum lines behind the firewall or does that chassis line directly plug into the HVAC module? Reason being is that I'm trying to check all my vacuum lines for cracks and such.

I believe the HVAC is the only "chassis" user of engine vacuum inside the car and so it would make sense than the HVAC is the only module receiving vacuum.

FWIW, you are much more likely to find a vacuum leak under the hood than in the passenger compartment. The underhood exposure of vacuum lines to ozone, oil, extremes of heat & cold, solvents, oil and gas never happens to under-dash lines and they should basically last the life of the car (if not longer...)

Do you suspect a vacuum leak under there because the HVAC isn't working correctly or because you have a driveability problem?

 

[Maxium]

No, I don't suspect a leak in the passenger compartment and my HVAC works fine. I was inspecting my vacuum hoses under the hood and found a cracked line to my fuel pressure regulator. I previously tested my vacuum with a gauge and I was getting good vacuum (22 in hg). I replaced the line but it made me want to go over ALL the lines just in case. I realized that one went into the "chassis" and upon doing some searching online, not many people talk about that line past that point and I just wanted to find more info on it.
I completely agree with your take on the vacuum lines inside being in a much more easy environment, but for some reason I would still like to take a look at them. Thanks for all the input!