Vacuum issue

1999 GMC YUKON
207,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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THE SALMON
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Just overhauled the engine but did not mark, or the tape fell off, 1 vacuum line and 1 vacuum port.
My PCV valve connects to the usual connector on the intake, but that connector has another tube that looks like a vacuum hose connects to it. What connects to that port? I also have a plastic formed tube with an rubber connector on the end. It's a little over a foot long and seems to snake around or through the engine. I kept it on the passenger side of the engine bay while doing the rebuild.
Thanks in advance.
Carl
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Dec 12, 2019 at 2:50 PM
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ASEMASTER6371
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Good evening,

I attached a vacuum diagram for you to view. See if it helps you find the routing for your hoses.

Roy
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Dec 12, 2019 at 3:00 PM
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JIS001
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If my memory is correct, that extra port is for the plastic vacuum line for your HVAC control for the blend doors. So if you were to start your vehicle and turn the A/C on then all the air would blow to the defrost.

When I worked at an independent shop I would remove the plastic vacuum and just run a rubber vacuum hose from there to the HVAC. Let us know if that is the case. And to be honest, the other end without the rubber looks broken. You will need to attach a rubber hose from that end to the HVAC if there is still enough hose at the end to attach.
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Dec 12, 2019 at 10:49 PM
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THE SALMON
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Thank you! You're a genius!! I had placed the Vortec cover and air intake hose on prematurely and covered up the broken side on the plastic hose to the HVAC. Your suggestion to just buy a piece of vac hose is a great idea which I will do! Believe it or not, I had done this same exact thing on another one of my vehicles 6 months ago! Was wondering why the AC would only blow through the defrost vents and then found a dangling hose!!
Thanks Again!!!
Carl P.
Dec 13, 2019 at 11:31 AM