VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Vacuum wiper motor

Hi,

I have a 1956 Bel air with a 6 cylinder.

I am pulling 17.5 vacuum at the intake manifold where the wiper is plugged into.

I took apart my wiper motor did a thorough cleaning of the motor and replaced the gaskets with new gaskets.
It is lubricated and moves freely by hand.

Before installing the vacuum wiper motor into my car, I ran the wiper motor vacuum line to the intake and the wiper motor ran strong, even turned off when I activated the switch.

Here is the problem; When I connect it to the car, it will not move the wipers. The wipers do move freely when I move them by hand.
Is the 17.5 vacuum at the manifold not enough to move the wipers.
Any ideas what my issue may be? Thanks.

When you replaced the gaskets did that include the perimeter seal on the flapper piston?

My experience is that it should not move freely by hand. You should feel the motor try to pull vacuum where the hose connects as you move the arm.

Do the wipers work if the windshield is wet?

Interesting. The gasket kit only included the 3 paper gaskets.

Is the flapper piston the part that rides in the casing? And I take it the seal is a square seal on the perimeter of the flap?

No, the wipers don't work if the windshield is wet.

You are correct about the seal being on the flapper piston. That seal gets hard with age and does not provide adequate sealing for the motor to work under load.

There are a few specialty places that rebuild those motors. Somehow they cornered the market on the piston seals.

If you do some searching on Chat and other sites you will learn a few tricks that sometimes work. The most common is to suck automatics transmission fluid into the motor. Let it sit a few days and see if things work better.

I soaked a flapper piston from a New Old Stock motor in transmission stop leak. It worked great.

There are a few people who have adapted Model A wiper motor seals or made seals from leather or other materials.

Thanks, that is some great information. I will take the unit apart again tomorrow and have a look at the seal around the piston. I will try to figure out a material I can use to fabricate a seal. If soaking it for a few days in fluid doesn't work.

Check the vacuum at the motor end to verify there is no leak in the system.

What would good vauum be?
I can't seem to find a leak but I haven't checked the vacuum advance unit yet. Thanks.

Seeing the motor turns good when powered direct to the intake manifold but not when using the contol switch i suspect the problem is in the control switch or its adjustment,
Make sure the cable is pulling the slider on the wiper motor to the full "ON" position.

Thanks, everyone.

I did disconnect the cable and activated the slider to the full-on position. When I hold it in my hand connected to vacuum, the motor turns well. When I slide the control switch to off, it goes off.

When I bolt the motor in, it will not turn the wipers in the full-on position.

The only thing I can think of is that I am losing vacuum somewhere, so I am soaking the flapper inside the unit in trans fluid that has a little stop leak in it. Maybe that will expand the seal around the flapper to hold vacuum?

There is also another small black circular material looking thing on the flapper that is probably original, but I do not know what that is and can't see how that would affect vacuum.

Gaskets are new in the unit, and everything seems there and in working order.

Vacuum at the motor should be near the same as at the manifold. If it is then you will know the problem is in the motor or wiper linkage.

You say it works until you bolt the motor into position... perhaps the shaft that goes through the body is binding and can not turn freely... after being bolted on... make sure the shaft will move freely........

That would be a good test. Install the motor but do not connect the wiper arms. See if it will run. Then connect one arm and check operation.

My money is on a bad piston seal. I had a motor that behaved the same way. Ran great when there was no load on it. It would work somewhat on a wet windshield at idle. When driving it would not work at all unless the throttle was closed and the car was rolling to a stop. That condition produces very high vacuum.