Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › Engine vacuum test Tagged: Vacuum test This topic contains 2 replies, has 2 voices, and was last updated by bill cruz 3 months ago. Creator Topic June 24, 2020 at 5:46 pm #958298 bill cruzParticipant 2009 Silverado 5.3L Flex fuel.Where is the vacuum port? Creator Topic Viewing 2 replies - 1 through 2 (of 2 total) Author Replies June 24, 2020 at 5:53 pm #958299 Richard KirshyParticipant If your looking to test vacuum you can use the brake booster port on the intake to hook a vacuum gauge to. June 25, 2020 at 6:25 pm #958343 bill cruzParticipant Thanks I just wanted another opinion because I just got the truck and to be honest I was a little overwhelmed by all the new stuff in the eng area.Had been driving a 1989 Astro. Bill Author Replies Viewing 2 replies - 1 through 2 (of 2 total) You must be logged in to reply to this topic.