DE

<center><img src="http://pictureposter.audiworld.com/103000/dsc01658.jpg"></center><p>Has been months since I looked at this 93 90s FWD engine bay. Ready to put it back together after the heads were off. I found homes for everything, except this check valve with two hoses, that is from a single line coming from the left fender vac. bottle. Not thrilling stuff like VAP posts but it surely would help me out. Did the forum search, nothing even close. Thanks

independent77

looks like the brake booster to manifold line is missing. Is that not the line in your picture?

DE

The brake booster to IM is a larger hose with several connections coming off it, I have that one but maybe I'm misunderstanding you. Could you clarify? Thanks for the response regardless.

DE

Yep..... you are correct, not in the picture but accounted for. Red circle is for the check valve just to the left of the booster. On top (almost) of the heater core hoses. Hope that helps.

Luxus Panzer

one that says "to TB" in your pic goes to the check valve in the line that goes form the front of the I.M. to the brake booster.

The one with the ? in your pic...hummmm I forget where that goes, either thru the firewall to the cruse control or thru the firewall to the HVAC area foe some kind of flap.

Lago Blue

<center><img src="http://pictureposter.audiworld.com/103000/dsc01658.jpg"></center><p>
...and some further questions (please confirm/refute/add your two cents, etc.)

Non-illustrated as least as far as I could find. This is just a humble attempt to document the subject hoses, associated components and their purpose. I don't believe my set-up has ever been tampered with, but you never know.

BTW, the example I'm using is a '93 90CS manual quattro w/AC, your FWD may differ?

Inside your circle above under the question mark is a blu/wht assembly (attached to the heater hose) I'm calling the Secondary Vacuum Check-Valve (SVCV). It traps and holds vacuum in the two hard black hoses, one you've pointed to, the other you've described.

On my car, the small soft hose your question mark points to (still the one in the circle), connects to a small black hard line running diagonally down and towards the right side of the car and disappears into the rubber boot for the A/C tubes on the firwall beneath the Cruise-Control Vacuum Pump. The larger one goes left into the left fender-well by the windscreen/lights washer fill-tube.

I've never followed them to exactly where they go. The small one may be HVAC flap control, the larger one may in fact go to a vacuum resevoir. All I did was confirm these two passed the leak-down test.

Re: "To Throttle Body?" in photo above. Not on my car, mine is as follows:

The Secondary Vacuum Check-Valve is supplied vacuum via the soft black hose (you point to with "To T/B?") which runs down and forward about six inches to a "T" which just hangs in space beneath the Cruise-Control Actuator. This "T" also routes vacuum to a small dark blue hard line which initially goes right, then immediately turns rear-ward 180° and disappears behind the RH side of the Brake Booster on the firewall. It may go to the pedal vacuum "switches" for the cruise-control? Again, all I did was check for no leak-down.

The above "T" is supplied with vacuum via a soft black hose which connects to the supply (Intake Manifold) side of what I'm going to call the Primary Vacuum Check-Valve (PVCV)(blk/wht item mid-way in the large black hard line which runs from the LH corner of the I/M to the Brake Booster. Like-wise, the PVCV traps and holds vacuum for the Brake Booster alone, that is why I'm calling it the primary.

I think that about does it, hope this helps. Any questions? Are there any different versions?
A photo or diagram of all this would be great.

I would like to add that I do appreciate any help or corrections anyone might offer that might be useful, thanks in advance gentlemen.

Lago Blue

Thanks Grillage,

Re: image from Vagcat.com

see larger image here:

https://www.audiworld.com/forums/sho...7&postcount=11

b4rs290

I know this is way late but ever find out where that line circled with the ? go to.

Lago Blue

has to supply vacuum to one customer AFAIK (the servo-actuator for the A/C flap, see actuator above item #14 in drawing above) which, as stated previously, is routed from the valve (also item #12 in drawing) in the above photo towards the passenger foot-well as follows:

"On my car, the small soft hose your question mark points to (still the one in the circle), connects to a small black hard line running diagonally down and towards the right side of the car and disappears into the rubber boot for the A/C tubes on the firewall beneath the Cruise-Control Vacuum Pump."