996 Vacuum Lines / Plenum hoses help

I was wondering if someone on here could offer some help, I've just replaced my exhausts for a milltek system and the old exhausts had what looks like actuators running off a vacuum line so I'd traced them back in order to cap them off but I'm not 100% how's the lines run, are the cross over valves still required if the exhaust are removed or do I still need them fitted? And does anyone have a diagram of the vacuum lines? My cars a 2000 3.4 c4 Thanks in advance for any help

Arghhh!!! You mean you stripped the PSE off? People pay thousands to fit them on. The tall black dome behind the alternator is the vacuum reservoir. Ideally, the redundant PSE vacuum lines should be capped off here (or more accurately, the four way spur replaced with a three way spur, or Y-spur with a straight piece etc) Unfortunately, it is not only behind the alternator, but below the induction "spider", so it is pretty inaccessible (unless you can tease the vacuum lines lines out between the major pipe work etc).

That's spot on thanks I only removed it because it was blowing and the valves had been welded open anyway! Cheers again

Would be really grateful if someone could help me out here. I’ve tried searching online but struggling for a definitive answer. So I have pulled the old engine from my 3.6 and have been transferring over a lot of bits to the new motor which is manual (mine is tip) these bits include coolant lines , the wiring loom , hoses and vacuums , plus also replacing other items (plugs , RMS , AOS , oil cooler on engine and box , water pump , thermostat, etc) I am pretty much now at a point where it is just exhausts to reinstall , however the vacuum plenum is confusing me. Can someone kindly confirm as to where each of the pipes go in the circled photo. Initially on the new engine this was a Y piece and it has now been swapped to a X with one end now going to the tip box , but I’d be really grateful for clarification on the connections for the other three ends (is there a drawing anywhere?) Apart from this everything has been relatively straightforward and hopefully be ready to fire it up by the weekend , Thanks in advance , Simon

thread merge also look at 996 secondary air injection valve replacement DIY All HVAC vacuum lines are fed from the solenoind bank behind the control unit in the center console.

Thanks so much , really appreciate this Think I’ve got it plumbed in correctly now

Apologies for the thread resurrection but thought it might be better than starting a new one.... I recently removed the starter on my 996 and feeling around I found a Y piece with a short vacuum line that wasn't attached to anything. I'm a bit worried I might have pulled it out of something while I was removing the starter. I think it should go to changeover valve #2 for intake SAI, according to the photos but I can’t find that valve. I’ve circled the loose end but can’t find anything this might fit into….. It’s a 996.1, 2000 C4 (e-gas throttle)

the valve is in the background within the red circle. You can see the connector more clearly in your photo.

Thanks! Unfortunately found the other end - it hadn't pulled out - the vacuum line had snapped and to get to it going to need to take a lot more bits off.... Managed to snap another hose connector for something else while I was rummaging around. 25 year old plastics really do get brittle!

Yes that’s unfortunately common. It might be best to snap them all and replace!

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Yeah, ordered a length of it to redo a load of them. Was wondering how you stop them coming out/creating a decent seal. The one part I took out had a bit of a lump/ridge in it to hold it in the rubber connector.

The vacuum from the engine ought to seal it well enough, especially as time passes on. If you’re still concerned about the fitment, you can use zip ties or tiny hose clamps.

Thanks