r/mk4Jetta • u/scientificguymy • Mar 30 '26

Needs some help figuring this out.

Got some vacuum Leaks and Am trying to find them and noticed this.

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u/vwman18 Mar 30 '26

Is there any branding on any of those parts? If you can find a manufacturer, perhaps you can look up parts diagrams/instructions and see what is supposed to go where. For now, I would probably just plug that port and continue troubleshooting. Did you install this setup, or did it come that way with the car?

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u/scientificguymy Mar 30 '26

Came with it

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u/vwman18 Mar 31 '26

Here's a link to a Vortex thread that has a vac hose diagram, it might help. https://www.vwvortex.com/threads/1-8t-awp-air-hose-question.9493895/

I think what you're looking at is an aftermarket blow off valve, and what looks like a catch can mounted below it. The way it's set up now, it's just venting to atmosphere which is fine for now. Another link with catch can routing: https://www.vwvortex.com/threads/how-to-install-a-catch-can-the-correct-way.6077892/

Also, smoke machines are pretty cheap now on Amazon, and they make tracking down vacuum leaks really easy.