Re: 52 250 Wipers

Posted by HH56 On 2021/7/18 17:07:57

Correct. Manifold to vacuum pump outlet, vacuum pump inlet to wiper motor.

If that missing vacuum pump is the only thing you found wrong with the plumbing I doubt you will see much improvement in the wiper action. Probably 99% of the time the manifold vacuum is all that is used. The strong manifold vacuum keeps the valves in the vacuum pump wide open so the pump cannot work and is effectively just a pass thru section of tubing. When manifold vacuum drops due to load or a wide open throttle to a point it is less than what is needed to keep the valves pulled against their springs the loss is enough to let the valves close so the pump can actually start working. The strength of the vacuum produced by the pump is a bit less than normal manifold vacuum would be and the volume is considerably less than the manifold can supply but the wiper motor does keep working -- usually at a slower speed.

The input vacuum port on the Packard motor is the one pointing toward the passenger side. The port on the drivers side is there to supply vacuum to the optional windshield washer. It is made active by the driver rotating the wiper knob toward the front of the car which is opposite the direction used to turn on the wipers. Knob turned forward and being held against a spring for a few seconds moves the slide valve on the motor to turn on the vacuum at that port. Vacuum to the washer lets the piston in the washer be pulled up against a heavy spring to fill the water end. Releasing the knob lets the spring push the piston down again expelling the water and continued turning the knob in the regular direction starts the wipers.