Brake vacuum line -- where do it connect?

Hiya Mike,

The brake booster vacuum line should connect to the intake manifold just under the carburetor. And when looking for this connection, be careful.......... Busses equipped with the brake booster (those after 1970) have a special manifold. It has a large nipple to fit the hose leading to the brake booster. Don't confuse it with the smaller nipple manifold sometimes used in Beetles. I mention this because I have seen Beetle manifolds in Busses. Many times! By the way, if you find you have to go out and get a new manifold, a manifold from an AutoStick Beetle WILL work.

Mike

1970 Bus - The Ruptured Duck

There is a check valve in that line to the servo near where it connects to the intake manifold. This is to hold pressure out of the servo & line - that is, once there is "vacuum" equal on both sides of the valve, the engine vacuum can decrease but the vacuum on the servo side stays the same as it was until you use it. If there is a momentary pressure on the engine side (backfire?) it will not blow out the vacuum servo diaphragm (but it might blow the hose off the manifold!) Whatever the maximum engine vacuum is between brake applications, that is what the vacuum in the servo line is at if the check valve is used. They are available - I just replaced a perfectly good one with a perfectly new one. If you get Inge to clamp her lips around your hose, she should be able to blow but not suck - at all!

-- Dave "Busahaulic" Pearson Fall City, Washington Remove obvious from addy to e-mail

manifold just under

careful..........

have a special

to the brake booster.

sometimes used in Beetles. I

Busses. Many times!

manifold, a manifold

Dave:

There is a little metal thingy in the line in the engine compartment. Looks to be about the diameter of a 50-cent piece. Would that be the fabled check valve that poor Inge might go crosseyed trying to suck on?

Ruptured Duck Mike:

Nope -- not seeing it. I have dual carbs on my 1776 engine, and no matter how much I peer under or behind where the vertical intake manifold things hit the engine, I can't see any hoses.

Anyone have a suggestion how I can locate where the brake servo vacuum hose connects to the engine? Other than taking the whole darn engine out, of course.

If you have a set of duals you will not have a hook-up for the vacuum, you "could" fabricate one running two T's from each manifoild, you would need to run check valves also... Basicly a total custom setup... Unless you want to go back to the stock setup...

J.

Hiya Mike,

1776 with duals? I has assumed a more or less stock 1600 set-up.

In any event, that's probably why the PO just rolled up the vacuum hose and stowed it. I have heard in the past that it is possible to adapt those intake stands to accomodate a vacuum fitting. But, IIRC, that involved some drilling and extra tubing. I'm sure somebody out there in RAMVAland has done this already and knows the exact answer.

Mike

1970 Bus - The Ruptured Duck

Hang on now -- near as I can tell, the brakes are working just fine. So I must be getting vacuum from some place.

No, I'm not at all interested in changing things. Yet the brake servo is getting vacuum, because the brakes work great. So . . . what's missing from this picture?

Kadrons, right? All the K-dog setups I've seen had a ballance tube running from one manifold to the other. Not sure what the purpose of that tube is, but it would be a handy source of vacume.

Max

Mike - I'm gonna say this once and I'm gonna say it loud:

IF EVERYTHING'S WORKING FINE DO NOT CHANGE ANYTHING.

Max

The balance tube is to even out the suck on the 2 carbs. Since you get 2 sucks from one side followed by 2 sucks from the other, the second suck cylinder - the front 2 - on each side - get a little starved for mixture, so that balance tube is to provide some amount of compensation from the other side to the second sucking cylinder. It also keeps the air/fuel mixture flowing thru the carb more evenly at all times. That's why it's better, but not really crucial, to have your manifolds installed properly left side / right side, because the balance tube nipples should be facing forward. Ask me how I know it works fine the other way around, with the nipples facing the bck of the vehicle?

- Tom

Kinda good advice. It depends on just how ignorant the person is (ignorance is not a bad thing - just an unfortunate thing.) If a person has never driven a properly running version of their car and is happily driving along with a burned exhaust valve on #3 such that he is only getting around 50% of the design output of the engine, I guess that's okay! To them, it's running as well as they know. They may notice other cars similar to theirs passing them on hills and begin to wonder, and the noise may be an irritant...

It sounds like Mike's got something that a P.O. has pretty badly bastardized. There's a lot of that out there (Like my own bus which I have personally bastardized beyond any possible point of restoration to "original"!) He has no previous experience with buses to tell him whether whatever it is, is working right or not. It seems to. To him.

- Dave

wrote:

just fine. So

The vacuum booster on your MC is exactly that, a BOOSTER. The MC will work just fine without vacuum, but it will require more force from your foot on the pedal. If you give it vacuum you will not need to apply as much pedal force when braking.

If you want to enable the vacuum booster in your car you will have to connect its hose to a source of good vacuum, with the check valve pointing toward the engine. The dual carb balance pipe is a good place to add a vacuum port for this purpose.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I don't follow. Do the manifolds for other single-throat dual carbs also have a ballance tube? The sequence of intake pulses would seem to be the same no matter what carbs are mounted.

The manifolds I have are symetrical (the same forward or backward). I don't see how it could make any functional difference which way they are mounted. In fact, my manifolds have been modified such that the tube fittings are on the inside instead (toward the fanshroud) of the outside of the manifold.

http://63.230.74.177/misc/kadrons/ I personally like to run the ballance tube in front of the shroud for a little cleaner look.

I do know that when I pinch the tube off to sync my Kads, the idle isn't as smooth.

Max

Yes - I kinda agree with you too, but it's "brakes", not a burned #3 exhaust valve which is a bit harder to diagnose the condition of. Brakes work about the same on all cars, and Mike's been driving for a lot of years. He could try locking them up at speed on a slippery flat road, and check the van's tendency to maintain a straight skid on all 4 wheels, just to check.

If it were an experienced mechanic I'd say fix it, but it's Mike. How much worse could he make it by messing around vs. how much better could he make it when he says it's fine?

BTW, does that booster affect only the front (discs?), or is it all 4?

wrote:

And I'm gonna have to tell you that if you read my post really, really, carefully -- you may need to move your lips -- you'll see that I WAS NOT TALKING EVEN FOR A SECOND ABOUT CHANGING ANYTHING!!!! I WAS ASKING WHERE THE FRIGGIN' SERVO VACUUM LINE CONNECTED -- THAT'S ALL!!!

Jeez.

Who says it's broken?

Guys. Listen up. I'm slowly cleaning up little messes that the PO left behind. Got the old A/C unit scraped off the bottom. Got dual carbs professionally installed. Replaced the leaky heater boxes. Replaced the failing starter relay. Re-installed the back-up light wiring. Lots of other tasks too trivial to mention. I've been eyeing this hose. Traced one end to the brake servo this morning. Studying really hard I can't quite see where the other end is connected and asked online where it is supposed to go. Received interesting information that this line usually hooks to vacuum, but since I have dual carbs, it's unlikely that it presently hooks to vacuum. I note that the brake performance is the same now as it was prior to changing to dual carbs. So either it was never hooked up in the first place, or it is magically getting vacuum now. The brakes feel great -- I mean great. Feel like power brakes to me.

I will run some tests based on some good suggestions. But hey! Relax guys, I appreciate the concern for the life and limb of someone you've never met, and the innocents he might take out, but I don't have enough experience to start disconnecting hoses and shit that operate things that affect safety. I'm just seeking information on how these things work, how they are connected.

As it stands, one end of the hose goes to the servo, the other end, when enters the engine compartment on the port side, seems to head to the starboard side forward of the shroud. I dunno where it comes out and would like to figure that detail out.

Maybe Kadron is the only one to do something about it. A friend bought my set for me in Houston years ago and brought them overseas for me with no installation instructions. I put them on, blew a lot of black smoke with the bus, changed the jets smaller and sorted it out. I had thought the balance tube nipples were for vacuum connections, and I had an 050 distr. so I just plugged them.

One day some guy asked me why I didn't have the balance tube installed, and told me about it. He also pointed out I had the manifolds on back to front. So I never changed the manifolds around, but I did unplug the nipples and stick a piece of hose in there. What a difference it made in smoothing out the roughness that I had thought was just natural, especially at idle and lower speeds.

I had a look at where the nipple sits with respect to the inside of the manifolds, and I agree - it doesn't seem to matter whether they are on the front of the engine side of the manifold or the back

- I expect there are various fabricated and cast manifolds available for Kadrons, so I guess no 2 will be exactly the same.

Sorry all to f*ck.

I shall henceforth refrain from responding to your posts.