vacuum manifold

[alzink]

For a 55 cadillac does the vacuum manifold serve any purpose other than providing multiple vacuum connections for wipers, oil pump, windshield wiper and antenna or is there something inside the manifold that regulates vacuum. Many thanks

[David King (kz78hy)]

If you are referring to the aluminum manifold/check valve that is mounted to the dash panel and has 4 hoses connecing to it, then yes, there is something inside.  On the 54-55 cars, there is a port that goes through the dash and has a hose that connects to the radio antenna vacuum port on top of the radio.

There are 2 valve ports with a spring loaded flapper valve which can close a port when low vacuum occurs. I made up a new valve/seal to replace the hard and likely broken one which is in there.

https://keepemrunningautomotive.com/shop/ols/products/wiper-check-valve-seal. 

You can purchase through the website or send me a check (preferred).

[alzink]

Many thanksI would assume that eliminating the radio antenna and washer (which I did) the other things calling for vacuum are the wipers and oil pump vacuum. Do I need to isolate those two in order not to lose vacuum for the wipers?

Thanks again David

[David King (kz78hy)]

That check valve is for the wiper motor.  The primary vacuum source is the manifold vacuum.  When it is low, the check valve closes the manifold port and the engine vacuum pump takes over.  There are light springs in the unit that hold the flap/seal closed and the strong vacuum overcome the springs to open them.  Those 2 ports are marked Vacuum Pump (VP) and Manifold (MAN) and are the vacuum source.  You need to plug off the washer & antenna ports if they are not used.  The wiper motor of course needs to be connected.

[TJ Hopland]

Interesting.  The vacuum pump isn't 'strong' enough to be the primary source?  Most years in the vacuum wiper and power brake era brakes were vacuum to right?

[Roger Zimmermann]

Interesting.  The vacuum pump isn't 'strong' enough to be the primary source? 

No. The vacuum pump must have some RPM's to be effective: it is located under the oil pump and turns at the same speed.