96 K1500 Mystery Vacuum Line?

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by simplyxtwisted, Jan 24, 2012.

  1. simplyxtwisted

    simplyxtwisted New Member

    Hey guys, new around here. Liking it so far. Hoping to get some help with a question.

    In the process of fixing a couple of other issues, I found this part...which Chilton has labeled "EVAP Vacuum switch" from what I can discern ( I am probably wrong ). It is on the passenger side of the engine. Thought it was the canister purge solenoid at first but it doesn't match up with any pictures I can find. The line coming out of the front goes back across the engine and over to the fuel vapor canister.

    #1...what is this thing?
    #2...there is a vacuum line that comes off the left side that leads to well...nothing. Right now its just an adapter with no line at all connected to it. Can someone tell me where this is supposed to connect to if in fact its supposed to connect to something?


  2. janikphoto

    janikphoto Rockstar 3 Years 100 Posts

    It's dark and raining outside right now, otherwise I'd just go follow it and tell you. I think that's the one that travels to the other side of the engine. Is it the hard plastic tube or a soft rubber tube?
  3. simplyxtwisted

    simplyxtwisted New Member

    The one coming off the front of is the hard plastic tube, that one goes to the fuel vapor canister, no mystery there. The one on the left is the mystery as the only thing attached to whatever this entire thing is, is the end adapter for the vacuum line so I don't know if its supposed to be hard or soft or where its supposed to lead.
  4. Dantheman96

    Dantheman96 Member

    It connects to a vacuum canister down by the heater hoses under the airbox. I'm not sure what it does.

  5. simplyxtwisted

    simplyxtwisted New Member

    I was under that what you are referring to is the heater water control valve, which connects to a valve near the firewall. See image below:


    What I am looking for is over the passenger side valve cover...it has 1 electrical connection and 3 vacuum lines...2 are connected...1 goes to the evap canister on the front driver side by the headlight...the other goes to another part that is supposedly the evap canister purge solenoid valve. This 3rd line..well...its still a mystery to me.

    I took a couple additional pictures to give a better idea of its location and the line I am talking about.

  6. Dantheman96

    Dantheman96 Member

    Here is some better pics of my setup:

    gmtc 006.jpg

    Notice the long vacuum tube running from the the device in the above picture wraps around the back of the receiver/dryer and hooks into the front port of the canister:

    gmtc 007.jpg

    If you look closely, there is a second port on the rear of that canister, and that is where the other vacuum line runs to the port near the firewall. The factory diagram you posted shows where that rear port connects, but it shows it hooking to the front port of the canister for some reason:

    gmtc 003.jpg

    The other port above where that rear port vacuum line hooks, runs across the intake to the pcv solenoid.

    Attached Files:

  7. simplyxtwisted

    simplyxtwisted New Member

    Thanks Dantheman, that extra bit totally cleared it up. And yeah, until you mentioned it I hadn't looked at the back side of that canister and seen that I had not one but two vacuum lines that weren't hooked up to it. Rerouted the one from the firewall to the back side of it, ran the one from the other part to the front of it and at least everything is hooked up now. Granted, it doesn't seem to have changed anything and there was nothing necessarily wrong in the first place but I feel better not having loose ends in there anymore.

    I was kind of hoping it would cure my lack of heat to the back vents by some stroke of luck but it looks like I'll be digging into the read heat unit to see what the deal is back there.

    Thanks man, appreciated!
  8. Dantheman96

    Dantheman96 Member

    No problem! That's what we're here for - to help each other with our rides' problems. Now I just need to find out why my idle doesn't drop back down to normal after I cleaned the throttle body.
  9. simplyxtwisted

    simplyxtwisted New Member

    You tried the idle air control valve? Had to replace mine not too long ago. Infrequent stalls when coming to a stop...then high idle...then all over the place idle and broke down. Progressed over the period of a month or so. 10 minute fix, part isn't terribly cheap though.
  10. Dantheman96

    Dantheman96 Member

    Yes I did replace the IAC. Nothing changed. It was a cool $80. :gasp:

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