Two engine hose questions - 74 Bus

[livingskies]

I'm now working on reconnecting multiple vacuum hoses and pipes in the engine bay. Most of it I have figured out, but two questions remain.

Question 1. The underside of the plastic piece that joins the air cleaner to the right side carburetor has a part with two small hose fittings. According to diagrams that I found, one small hose should run from there to the air regulator (the regulator that draws air in a larger pipe (now reattached) from the area above the battery). I have a piece of small diameter hose that I can use for that small hose.

The second small hose fitting is broken off under the piece connecting the air cleaner to the carburetor. It appears that second small hose should connect to a junction block (vacuum?) above the center of the engine. The hose is still there, but has a screw stuck in the end to block it.

What is the function of those two small hoses and the fitting that they attach to? How important is it to have that second hose (or the first one) connected to the piece that connects the air cleaner to the right side carburetor? Will it make any difference to have them disconnected and blocked off?

I hope that makes sense; it likely will to someone familiar with the '74 dual carb engine.

Question 2. The charcoal cannister has two hoses coming off the right side. The larger hose is still connected, but the smaller hose is hanging loose, not connected to anything at the other end. It has a metal tube type fitting inserted in the disconnected end. Can anyone tell me where that should go? It looks a bit like an insert fitting for a carburetor. And is it necessary to have that connected?

Thanks in advance for any help.

[Wildthings]

I believe you are talking about the thermostatic valve that operates the flap for the intake air preheat stove. The intake air preheat stove provides warm air to the carburetor during cold weather and warmup during warmer weather. It should let the engine run smoother and prevent stalling and should give you a bit more gas mileage, maybe even a mile or two per gallon.

The one hose should connect to manifold vacuum and the other goes to the flapper valve. It is important to have the hoses connected to the correct side of the thermostatic valve. For the intake air preheat stove to work you need all the pieces in place otherwise its not worth fixing. The thermostatic valve is like filled with crud at this point and needs to be soak with carb cleaner and blown out with care.

The small hose is #9 in the below picture. One of the larger hoses goes to a nipple on the left side of the fan shroud and the other hose runs to a fitting on the air cleaner housing.

[busdaddy]

[livingskies]

Here are a few pictures that may help identify where the hoses go.

Regarding Question 1 above:

This is the right air horn with the piece with two places for hoses to connect. As you can see, the plastic connector is broken off, leaving not enough to connect a hose to.

Based on the diagrams that I have found, the metal (brass) tube may (or not) connect to the air regulator that in turn attaches to the air cleaner. Am I on the right track with that one?

It also appears that the small hose from the broken fitting should run to the air vacuum junction below the air filter (just left of the pinched off metal line) -next picture:

Is this correct? Or ???

Regarding Question 2 in the original post:

Here is the line, which is loosely attached to what appears to be the charcoal canister:

Where might the other end of this go? It has a metal insert in the pipe, that may or may not attach to the right side carburetor. Here is that carburetor, with a short piece of blocked hose projecting from it. Might the hose from the charcoal canister connect to that carburetor at that spot?

[Abscate]

It’s the thermostat part of the air motor, regulates temperature of incoming air

I think one side of the nipple takes manifold vacuum, the other goes to the vacuum motor on the air cleaner air door
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[busdaddy]

Good job on conquering the picture issue, thanks!
the aircleaner thermostat is explained here: https://www.thesamba.com/vw/forum/viewtopic.php?t=691091&highlight=cleaner+thermostat the small hose on the charcoal canister goes to the tank vent line(s), that Ratwell link should explain it.
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[livingskies]

busdaddy - I looked at the ratwell link and don't see a reference to this "the small hose on the charcoal canister goes to the tank vent line(s)." Where would I find that connection to the tank vent line? Thanks.

[busdaddy]

You need to spend a day looking over www.ratwell.com , if you type "vapor" or "charcoal" or maybe "canister" into the Google search bar on it you'll be deluged with all sorts of interesting things, likely some may even apply to your situation. Sooner or later you'll find what you need, but be careful, you may learn about all sorts of other things you didn't even know mattered....., until now.
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Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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[Wildthings]

[SGKent]

the temperature part comes up in other discussions:

[SGKent]

also check this link out to see if any of these are the system you have:

http://www.michaelknappmann.de/bulli/michaelk/vw_bus_d/fiche/t201600.html

also

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[livingskies]

OK, some of this makes sense, or does it? Please bear with me.

#9 hose: does this somehow connect from the charcoal cannister to the two metal pipes (one painted orange and the other one plain metal) that almost meet just behind and above the hinged engine compartment lid? One has a 90 degree bend and fits in a clip from the roof of the engine compartment, and the other one just ends there - hangs there loosely, without any support. Does that small hose from the charcoal cannister connect with these two pipes, using some sort of a missing fitting? Or?? If so, what does that fitting look like? See pic below of the two hard lines and the soft line:

I had noticed those two metal pipes days a while ago, and then they slipped my mind. Had no idea what they were - it's starting to make sense??

I'm also posting a picture of the box that connects to the air cleaner. It sounds as if a hose from the brass fitting on the right side air horn connects to that connection on the box. Yes?

If I understand ratwell correctly, the hose from the second nipple on the air horn should run to a "brake booster tee" on the right side carburetor. Or does that hose run to the vacuum fitting (just to the left of the pinched off pipe) shown in this picture below?

[SGKent]

the two long metal tubes come together with a weird tee. That provides fumes from the tank. Those fumes go into the small hose of the canister. Where the fumes enter the canister there WAS a filter made of something that turned to gel long ago and nothing can get thru. The canister lid pops off and there is a whole bunch of carbon pellets in it that store the fumes. They get replaced with activated carbon pellets, and I used a piece of red scotch brite pad designed for chemicals to use a filter to replace the icky sticky gooey gel that was a filter once. One of the big ends goes to the side of the shroud where air is blown into the canister. The other big end goes to the air cleaner. How it connects depends on what kind of air cleaner you have. Late air cleaners have a vacuum acutuated purge valve on them. Early oil bath air cleaners it just goes to a port on the air cleaner and dumps fumes there.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[SGKent]

some have a metering orifice, some do not. The photo Mike put up is a really good single image how they work but these other images I hope helped. It is a confusing system because while it is the same from about 1972 - 1977, with minor changes in 1971 and 1978, there are some slight variations between years. I have never owned a 1974 bus, let alone an original 1974, so the images of where the factory hoses routed is not burned in my mind. This is the part number of the weird tee 211-201-405.

[SGKent]

also I think but am not sure that the air intake motor on the top of this picture gets its vacuum from the thermostatic switch that you showed one nipple broken on, and then the other side of that switch gets its vacuum from the manifold vacuum. I don't know how that system is designed to bleed off vacuum so the motor closes and opens at the right pressures.

_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[livingskies]

Merlin, I think you may be correct on that - was more or less what I was thinking by now as well. The line from the brass nipple underneath the right side air horn likely runs to the plastic nipple on the air intake motor. A line from the broken nipple under the air horn likely runs to the manifold nipple (with the hose currently blocked off (with a strip of green masking tape on it).

If that is correct, then all I need to do is figure out how to reconstruct that broken plastic nipple, so that I can fit a hose back onto it. Unless that part with the broken nipple is still available - which I doubt.

I see that the rubber tee for the fuel vent system is available from CIP. Or is there another source that would work better?

It's probably confusing to combine two topics in one thread - sorry about that.

[SGKent]

[Abscate]

[Wildthings]

[livingskies]

The charcoal canister now has a new line running to it from a new tee that joins to the two fuel vent pipes from the left and right sides at the rear of the bus. These missing parts also could have contributed to the fuel odor when the tank was overfilled. Also, two short hose joiners between metal vent pipes replaced. Hoping that looks after it for now. We will see.

Regarding the other issue, I may have found a work around for the broken nipple on the bottom of the plastic air horn that fits onto the right side carburetor. Not sure if this assumption is correct or not (please correct me if this is not correct), but that controller with the broken nipple appears to regulate the amount of vacuum reaching the motor that controls the flap that controls air flow to the air cleaner. Hooking the vacuum line directly from the manifold vacuum port to the air flow motor port should ensure that the flap is open when the bus is running. While that may not be ideal for cold operation, it should work fine when the engine warms up a little. Or am I missing something. If and when I can find a replacement part for the underside of the air horn, it is an easy matter to return this to stock.