dalspaugh

Hi all,

At a RallyX a couple weeks ago I noticed this vacuum piece was broken. It's on the driver's side of the intake manifold. Car seems to drive OK without it... anyone know what it does/where it goes? I see that it comes from the intake Manifold and goes to the brake booster on the other sides...

Thanks!

hubturn

I'm thinking you have a manual transmission. Be grateful. With the auto that pipe morphs into a contraption of senseless complexity. This is going to be a dealership item most lilely, and they will have it available. Chances are that they will call it a "pipe" and because of the way the plastic seals around the check valve on both ends, you will be getting the entire assembly. That baby is the vacuum check valve for the brake booster, and you need it.

dalspaugh

Yes, that does look like that's what it is. Thank you. Dealers seem want 110+ for the hose assembly... which is a huge bummer. I'm guessing the end that broke off is to supply vacuum to some other items in the car, but what? Anyone know?

Also, anyone know what this weird blue and black valve is when I search on 3rd party parts sites? It definitely does not look like the right part...

Thanks again Hubturn!

Rusty Spokes

You might be able to splice in a vacuum fitting into the existing hoses..about $38 from Bus Depot


http://www.busdepot.com/078133752f

Part #5

hubturn

With a closer look at your photo I now understand your concern. I could be mistaken, but you are referring to the open hole on the side of the vacuum check valve? I believe that was a small extension about a half an inch long that had a cap on it. I do not believe that it went anywhere. Ah, I just searched the forum. Read this. https://www.audiworld.com/forums/sho...um+check+valve
Hopefully, this picture will load.

dalspaugh

Ok, I like the idea of maybe tapping into the line before the valve, essentially doing the same thing. Just have to find the right sizes.

I don't have a rough idle right now, but I did notice that with the car idling, plugging that hole and unplugging directly affects the idle... But the car recovers after a few seconds. I'm guessing because it is accounting for the changing pressure in the intake manifold.

As for where the hose goes, it definitely goes somewhere because the hose dissolved in my hands upon investigation. It disappears over the back of the engine, I just haven't had the time to track it down. Thanks for the help guys.

hubturn

Sometimes there is a sticker under the hood that shows the vacuum line routing. It's near the drivers side hinge. You might have to crane your neck to see it. You are saying that a hose was connected to this projection on the side of the valve where the hole is. Was the hose a color other than black, such as green, brown, or blue? Vacuum leaks drive this engine crazy. You've got to figure this out.

grillage

That check valve is indeed capped on an automatic.

I believe it goes to the other check valve by the brake booster.

When I did my auto to manual conversion I had to change some things...

Andy1212

The nipple on the check valve is the vacuum supply for the diff lock. Mine also broke off and I currently have it plugged until i find a solution. Wont affect engine vacuum, your diff lock is now inoperable however.

dalspaugh

So this weekend we had some warm weather up here in MA and I had a free day so I tracked down a yard with 2 cars similar and went for it. They only had a piece from an automatic cabriolet from '96. But it looked about right so it took it for 10 bucks. Picture below, it is obviously not the same but It looked like it should work, just a bigger opening coming off the side so I just had to step it down.

So because of the horrid lack of good info on this car, I decided to just map out on a white board the vacuum system that I could see (manual with EGR). This also helped me ID about 4 either split lines or disconnected, as well as a handful of others that looked like they were about to go. I ordered two vacuum rebuild kits from Blauparts so I had a bunch of hose to use.

What I found was a completely broken brown line going to the EGR (hoping that explained the CEL, hasn't come back since this weekend) and it was unplugged at the other end. Also had a split in the light blue line that actuates the variable valve geometry (more power!? :-O) and there was of course the broken check valve and the hose that was coming off of that was completely dissolving.

So after mapping the whole system out I just started to replace everything that needed it, definitely helped me understand what's going on with the vacuum system, it's not just voodoo after all. In the end, the CEL is no longer! (fingers crossed), the intake sounds louder <4K!!!, but my diff lock still does not seem to be responding . I will admit that after 7 hours of vacuum work, I was pooped and not interested in climbing under to continue working. I will be checking out that problem another time, it has worked in the two years that I've owned the car so more diagnostic to come.

Thanks everyone for the help!

One last note in my diagram, all lines with a black dot were replaced and green ones seemed to be OK.