[Cloud9...68]

I've contacted a few individuals on this forum about this, so no disrespect to them about reaching out to a larger audience, but this problem has me stopped dead in my tracks, so I'm looking for any advice that can get me past it so I can more forward with my project.



Somehow, probably when I was cleaning and painting my intake manifold, I managed to lose that little round, 8 mm o.d. vacuum hose nipple that’s pressed into the lower left side of the intake manifold. It’s located right above the bracket that connects the intake manifold to the drivers side engine mount bracket, right below the casting plug on the manifold. It connects to a vacuum line, that goes into the tank venting valve, which goes into the vacuum valve that goes to the carbon canister. The purpose of these lines is to suck gasoline vapors from the carbon canister into the engine. This assembly is shown on illustration 201-15 in the PET. The tank venting valve is item 14 in the illustration, and the vacuum valve is item 15. Unfortunately, the fitting I’ve lost isn’t shown as a separate part number (it isn’t even shown in the PET, either for the 968 or the 944), so it isn’t available through Porsche.



So, my first question is, do I really have to have this vacuum line connected to the intake manifold? In other words, can I just plug the hole for the fitting in the manifold? A couple of problems I see with this approach are:

1. I’d potentially be venting raw gasoline into the engine compartment, and
   
   
2. I wonder if the other lines that are connected to the vacuum valve (namely, line 13, which connects to the throttle body) require the manifold vacuum to operate properly. The fact that the inake manifold is pressurized on supercharged engines argues against this, though.
   
   

8 mm is very close to 5/16”, so I figured I could just buy a short piece of 5/16” tubing, and flare it using a flaring tool I could borrow from Advance Auto. Unfortunately, I’m striking out finding a piece of tubing of this diameter locally. I could order one, but that would further delay my project (gotta start thinking about who to will this to, because I’m not convinced I’m going to finish it in my lifetime…), plus the shipping costs over ten times (I’m not exaggerating) what the piece of tubing costs. We have a Grainger locally, and they actually have the tubing in the right o.d., but the minimum length they’ll sell me is something like three miles….



Does anyone have any idea as to how I might get my hands on this vacuum fitting, short of buying a new intake manifold, or what I might be able to fabricate to substitute for it? This part of the engine probably doesn’t get terribly hot, so I’m wondering if I could get away with a plastic vacuum fitting, if I could find one of the right diameter. Thanks.

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[flash]

re 5/16 tubing: you could probably jb weld a barbed fitting in there. you can get one of those at pep boys. plastic won't work. it does get too hot for that.



re vacuum at throttle body: that is ported vacuum and is needed for off throttle idle recovery. if you look at the inside up at the top, you will see a small hole right in front of the closed throttle plate.

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[Cloud9...68]

[quote name='flash' timestamp='1356553630' post='136646']

re 5/16 tubing: you could probably jb weld a barbed fitting in there. [/quote]



Thanks for the tip - looks like this will do the trick:



http://www.grainger.com/Grainger/Hose-Me...Pid=search

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[durtkillon]

If I recall correctly, the vac line from the throttle body opens the vent valve from the cannister. The line to the intake sucks the fumes out of the cannister where they are burned in the intake. The valve should open at start up and funtion normally, drying out the cannister. At boost, it should act like a parked car and filter the fumes out and send them to the back of the car. Not a big deal.



If you disconnect and plug the 5/16" intake line, I would think you would want to plug the throttle body vac line as well otherwise you will vent the cannister to the engine bay every time you start the car. Long term, the cannister would probably get saturated as it would never dry, particularly on a hot day when your tank fumes a lot.



Do you notice fumes now with the line disconnected?

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[flash]

yeah- that's the kind of thing i was thinking. seems like it should work.

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[Cloud9...68]

Durtkillon,



My car hasn't run since April of 2010 (been working on a looooooooooooong-term project to convert it to a mostly-track car), so I can't answer your question about fumes coming from the engine bay. Although, if I don't get it back on the road soon, I may be tempted to inhale some exhaust fumes myself <img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" /> .

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[MB968]

I like the idea of using the 5/16 tube, flaring one end. Flare the end enough so that you have to drive the tubing into place.



To secure/seal it in the manifold I'd use:

Loctite makes a product that can be used to fill the gap for a loose fitting bearing.

Or you could use an epoxy that will handle the heat

Or, I'd probably take the simple route and use the gray silicon RTV



Then once the tube has been driven in with the sealant, use a center punch to peen the end of the hole around the tube to create an interference fit where the tubing exits the manifold.



Edit, Forgot to add: When I pulled my engine, I found that the original tubing practically fell out of the manifold (maybe why you lost yours). I flared the end, used the loctite gap filler (which I already had), drove it in with a hard plastic hammer, and peened the manifold hole around the tube as mentioned above. I ended up doing this to three of the vacuum tubes that are in the manifold as they were all loose. So, you may want to tug on all of your lines while it is easy.

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[Cloud9...68]

MB,



Yes, the idea of using a 5/16" tube and flaring the end may be the height of brilliance (tongue firmly in cheek here) in theory, but unfortunately, I'm finding that 5/16" o.d. tubing isn't commonly used for anything. I call about a dozen stores and shops of every category I could think of, and nobody has it locally. It can be obtained through mail order, but the shipping is ridiculously expensive. So, I'm going to use some barbed hose mender, as shown in post #3 above, and secure it to the manifold with either JB Weld, or loctite retaining compound, although since 5/16" is a smidge larger than 8 mm, it should be a tight fit on its own.

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[MB968]

Barbed fitting is a reasonable alternative if you can't get tubing (I assume you've tried local hydraulic shops). Only thing I don't like about todays barbed fittings; the style being sold these days makes it very difficult to remove the hose without cutting it. Years ago the barbs were just rounded whereas today most are a sawtooth design.



You can probably make it easier for later removal by taking a long strip of sandpaper and using it like a strap to sand down the sharp edge of the sawtooth. It still won't make it easy because of the sawtooth nature of the barbs but you'll at least have a change at later removal. If I have to use these, I'll sand them down as much as I can and still have the hose push on. Then I use a hose clamp. Won't be as convenient

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[Grandpa#3]

Hi Cloud9, I located the nipple you are looking for in the 968 Parts Cat, but no part number for it. While you have the car down check out the Deflection Roller for the Throttle Cable. In the Parts Cat. the picture is illustration #107-05, item #8. My son found his friends 968 roller separating where the throttle cable has worn it down. The Vac line nipple is in the same illustration just above where #11 is bolted to the intake manifold.



Cheers,

Larry

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[Cloud9...68]

Thanks, Larry. I'll definitely have a chance to take a close look at the deflection roller for the throttle cable, because I found that the barbed hose mender I got is too big around to force into the hole in the manifold with the manifold on the car, so today's project will be pulling the intake manifold, which will give me a much better look at what I'm up against. This little excursion wasn't in the play book, but at least I don't have to be back at work until next Wednesday, so I still hope to at least try firing up the engine before then.

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[MB968]

Cloud, there should be plenty of stock on the barb that you purchased to:

- Chuck it in your drill, spin it, and use a file to take it down to a size that will allow you to drive it into the manifold. If you have a micrometer to measure it, you'll only need it to be a few thousands larger than the hole (which you should measure also as it may be oversize.

- While you are at it, also do the same to the opposite side of the barb to make it a reasonable fit for the hose.

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[Cloud9...68]

[quote name='MB968' timestamp='1356716053' post='136747']

Cloud, there should be plenty of stock on the barb that you purchased to:

- Chuck it in your drill, spin it, and use a file to take it down to a size that will allow you to drive it into the manifold. If you have a micrometer to measure it, you'll only need it to be a few thousands larger than the hole (which you should measure also as it may be oversize.

- While you are at it, also do the same to the opposite side of the barb to make it a reasonable fit for the hose.

[/quote]

Hmmm... I was wondering about how I might reduce the diameter of the barb, but hadn't thought of chucking it onto my drill and using a file. Thanks for the suggestion - I'll give that a try before removing the intake manifold.

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[Cloud9...68]

MB,



It's people like you that make this forum so great. Your idea to chuck the hose mender in a drill and use a file to reduce its diameter worked like a charm, and saved me having to remove my intake manifold. Here's a picture of the modified piece:



   



As you can see, I had to file a fair bit of it away to gets to fit in the hole, and effectively ended up with the elusive 5/16" o.d. tube. I then bought a piece of pre-formed rubber tubing designed for use in emissions plumbing, which had the perfect 90 degree bend, but was too short. So I took another hose mender, used it to attach to another piece of tubing I had lying around, and connected the other end to the check valve. Problem solved - thanks to all who offered suggestions.

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[MB968]

Looks like nice work. Glad you got it worked out.

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[flash]

woohoo! i thought the barbed fitting might work. cool!

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[Cloud9...68]

Yeah, glad to have this little obstacle behind me. This forum is definitely da bomb.

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