Vacuum manifold or valve

[Roger Zimmermann]

While I was explaining how to connect the vacuum hoses in a French forum, some clever guy told me that my own connection was wrong: I crossed the hose coming from the manifold with the one coming from the vacuum pump, see the wrong setting on the picture.
The man said that the dash pod should not be connected to the vacuum pump hose, but to the manifold vacuum. My candid answer was: "inside the vacuum manifold, there is one large chamber, it's not important!"
The reply was: "no, there are 2 valves inside that manifold, but usually they don't work anymore. Do the following test: if you can blow air in either vacuum ports, your manifold is defective"

By manifold, I do mean the small part attached to the firewall with 4 vacuum ports. On the second picture, you have a good view to that part.

Roger

[Roger Zimmermann]

This forum is sometimes funny with pictures...The first one did not appear. Here it is:

[Roger Zimmermann]

As you may see on the first picture, the ports from the manifold are labelled with the word MAN for manifold, V P for vacuum pump and WASHER for...washer. The forth outlet is obviously for the wiper motor. The part which is pictured is from a 1956 Cad; the same part was used till 1958. 1954 and 1955 have another part number, but I may imagine that the manifold is almost identical.

Of course, I did the test suggested by my friend and on the first manifold I removed, I could not blow in one inlet; I could do it without problem in the second one. This is the explanation why I have bad wiper action when the gas pedal is pressed beyond a certain position: low vacuum in the intake manifold, and the vacuum created by the pump is aspirated by the intake manifold, therefore no wiper...
It took more than 25 years to discover that, thanks to a gentleman 77 years old!

And how to correct the situation? well by opening the valve...After filing both rivets, it can be opened and is looking like the first picture below. The red gasket has ears; with the time they get hard and cannot close the port when necessary. There are also two tiny springs; they are OK when the material is fresh.

To repair the valve, I took a suitable material more or less like a fuel pump's diaphragm and cut it to the proper dimension, like you can see on the second picture.

At the end, I asembled all together with 2 screws (so it can be opened later in case) and did the test. It is OK! Now, I can repair the manifolds from my 2 othe cars...

Roger

[Roger Zimmermann]

OK, the first picture did not come. Here it is!

[walt chomosh #23510]

Now that's interesting!....thanks Roger!

[Roger Zimmermann]

You are welcome Walt! I hope that my explanation was clear enough. It's amazing: I have my '56 de Ville since more than 25 years and I'm discovering the secret of good functionning wipers after so much time!

Roger

[J. Gomez]

Roger,

The only thing I can say is "A M A Z I N G..!"  I always thought this was just a plain vacuum manifold w/no working parts…!

[Otto Skorzeny]

I'm a little confused.

So does the photo of the engine compartment show the correct connections and routing or is it incorrect?

[J. Gomez]

Roger,

I first tested mine with hand vacuum pump.  I closed both the “washer” ports and hook the pump to the “MAN” port and vacuum was escaping out of the “VP”port.  I then connect the pump to the “VP” port and the vacuum held slightly but eventually escaped from the “MAN” port. I took my apart and found the material was petrified and one of the tabs broke off, yes it was the "MAN" side.

I made a temp one from a small piece of 1/32” rubber and performed the same test, this time each port held the vacuum. So vacuum goes from either the “MAN” or “VP” to the washer side, but not between them.

Great 411…!

[Roger Zimmermann]

So does the photo of the engine compartment show the correct connections and routing or is it incorrect?

Otto, you would probably not be confused if the pictures were registered in the forum the way I wanted. I confirm the answer from Lou: in my picture, the hoses are crossed. It's not important for the wipers but it is for the dash pod. To avoid stalling of the engine, the dash pod must react according to the intake manifold vacuum.

For all with these cars: I'm pleased that my little report let you learn something. Forums are an invaluable way to share experience. I got this one from a French forum and, as a Swiss guy, I'm passing it over to a US forum!
I'm almost pretty sure that this attangement was shared by other manufacturers as vacuum wipers were common in the fifties. It's amazing that this little trick is unknown from the majority. Further, I have all "Serviceman" from 1953 to 1961. I don't remember that this little important part was discussed in these bulletins.

Roger

[Jack Mcilwraith]

Roger - great information. Like Jose, i thought this was just a piece of metal attached to the firewall. now I can have a look in the Spring and hopefully, fix my wipers.

[Walter Youshock]

Roger,

Thanks for the tip.  I rebuilt mine yesterday.  I never knew that was a valve--I just thought it was a 2-piece distributor.  It makes total sense that it would have to equalize or regulate the vacuum from "MANIFOLD" to "VACUUM PUMP".

I'm surprised that the wiper rebuilders don't ask for this part when they redo a motor.  Also, this leaking might explain why the washer jar will sometimes emty. 

I can hardy wait to get stuck in the rain!

[Roger Zimmermann]

I'm surprised that the wiper rebuilders don't ask for this part when they redo a motor.  Also, this leaking might explain why the washer jar will sometimes emty. 

I can hardy wait to get stuck in the rain!

Me too! However, I have to wait until next year as my cars are in the winter sleep now. As I have never water in the windhield bottle, I never had the problem.
Probably the people who rebuild the wiper motors don't know about this little part. I don't know if this part is to be found inder the hood of other makes at GM, Ford or Chrysler; anyway, not all the cars with vacuum wipers had a vacuum pump under the oil pump.
Prior to 1954, Cadillacs had a vacuum pump combined with the fuel pump. I'm wondering if there is such a valve assembly?

Roger

[Carl Schreiber]

All -

Nice post, Roger!

I thought everybody knew about this one!  Just make sure you get your springs back in the proper half of the valve body, on the proper side of the flapper valve.  They have to go in small-diameter side down (large-diameter side against the flap).  Thread the back housing 10-32, and a  button-head allen bolt works well to put these back together.  If you're really creative, you can shave the button-head down to rivet shape and size, screw it into place, then fill the allen socket with JB Weld (or similar) and paint to make it look like and original riveted part.

Carl Schreiber 

[Walter Youshock]

I used pop rivets that fit and it seems to work correctly off the car.

This really seems to be a critical component of the entire vacuum system, especially on cars without vacuum tanks--IE: Hydrovac equipped cars. 

Thinking of ow a loss of manifold vacuum occurs and that pump takes over, this unit makes sense.  Now, once this unit fails and manifold vacuum drops, think about possible drivability issues...  Could this be the "red Herring" of my hesitation issues?  Could the vacuum pump have been sucking power out of the engine because of a stupid, dried-out flapper gasket on the wiper circuit?

Without that valve, the entire wiper/washer circuit is open to manifold vacuum at all times.  A fully working vacuum pump really means nothing if that valve remains open to the manifold side.

[Roger Zimmermann]

I used pop rivets that fit and it seems to work correctly off the car.

  A fully working vacuum pump really means nothing if that valve remains open to the manifold side.

To reasemble, I used 3mm screws with nuts, it's the same diameter as the rivets. This way, it will be possible to open the part in case.
When I restored my 3 cars, I let overhaul the vacuum pump. It was a big deception when I had to use the wipers; they worked not better than before the pump repairs. Now, after this "discovery" I understand why!

[cadman49]

wow roger c, that info. you gave us on the vacuum/valve is the best thing i`ve seen in a long time; & i`ve been around a long time.now i can fix my 57.not much hope for my 49,so i put a 55 chevy wiper motor on it. fits perfect and & its 12v. now all we need is somebody to make up those gaskets; semi-pro,would make for some happy cadillac campers lol,lol--cadman49 (richard king,calif.)

[Christian Aicher]

Hello Roger,

I just stumbled over your excellent post and went straight out into the garage. I removed the windshield washer manifold - and of course I was able to blow into the VP and MANIFOLD connector. I filed the rivets of and found the gasket rock hard and brittle as seen in the picture. I made a new one and put everything back together. Now the car runs as before but the next time when I wash the car (wet windshield) I will try the wipers....

Thanks for sharing this info. Stuff like this makes this forum great.

Chris

[quadfins]

This sounds like a topic for an excellent and useful article for the Self-Starter. I suspect that many owners, who might be "internet-challenged", would benefit from this knowledge. Roger, would you consider submitting it (with photos) to Steve Stewart?

Jim

[Roger Zimmermann]

This sounds like a topic for an excellent and useful article for the Self-Starter. I suspect that many owners, who might be "internet-challenged", would benefit from this knowledge. Roger, would you consider submitting it (with photos) to Steve Stewart?

Jim

Jim, that's a good idea. I will try to recap what I wrote and send it to him.

Roger