The Stovebolt Site Forums The Shop Area General Truck Talk A vacuum wiper motor question

I had my vacuum wiper motor rebuilt. The truck is a 59 Chevy. This rebuilt motor is beautiful and works great on the bench. I checked if it seals vacuum in the 'off' position, and was surprised that it does not. Using my hand vacuum pump a quick squeeze pulls 15 inches of vacuum but it bleeds down to zero within a few seconds. It seems like excessive leakage to me. Is it normal for these to leak vacuum when in the off position, wipers parked?

Mark

It has been a while but I believe there is a valve that shuts off the flow while parked. It wouldn't be an absolute seal though. Try hooking it up to a vacuum supply and see if it hisses.

First off, who rebuilt your wiper motor? And no, if it's leaking
down then you have a vacuum leak, it's not sealing somewhere in
the circuit.
If it was simply taken apart, cleaned and the old power
piston/flapper re-greased, then it's going to leak. This is
what many people call "rebuilt". A proper rebuild installs a
new seal on the power piston/flapper and "new" gaskets. As far
as I know, the only one that still has any of those parts is
The Wiperman and they do not sell any of the parts for you to
rebuild them yourself.
I've tried: http://www.pbase.com/dennygraham/trico_wiper
http://www.pbase.com/dennygraham/spare_tyco_vacuum_motor&page=all

Denny Graham
Sandwich, IL

Rebuilt by wiperman. He does great work as I understand, but has not responded to my questions. I was just wanting to know if this amount of leakage is normal. It is not enough to hear hissing when hooked up to my regular vacuum pump.

Mark

Boy that's a surprise Mark, I've never heard of anyone having a
problem with one of their rebuilds.
I'm pretty sure they put all new parts into them. It might have
to lap in for a little while. I think I'd try running it for a
while and see if it seals up. In the mean time I'd stay with it
and keep trying to get hold of Bob Ficken to see what he says.
He is to wipers as you are to truck beds.

You're dealing with a very small volume and it only takes a tiny
leak to bleed a vacuum system that small up to atmosphere, so
you probably wouldn't be able to hear it.
Denny Graham
Sandwich, IL

I don't believe the valve in question relies on the seal of the flapper.

Yeah, that's true Fred, if it's the valve that's leaking down.
Could be bleeding from one side of the chamber to the other
though. Can't be a vacuum on both sides of the flapper or it
wouldn't move, so when there is vacuum on one side there's
atmosphere on the other.
Been a few years since I was into those so the complete circuit
isn't fresh in my mind.

DG

Hey Mark, Is the the dash control moving the slider too far?
Mine will also hiss air if I turn the knob to the off position too far.
I have to turn the switch on just a little bit to the on to make it stop hissing.
Mine is not rebuilt (yet) and I would think that its not suppose to do that after a rebuild.
Maybe cable is sticking?
Just a thought....... Jeff

Thank you for all the comments and suggestions. I am still testing it on the bench with my vacuum pump, not installed in the truck yet. I always like to test fit things before final installation. The wiper motor will be a bear to remove from under the dash when this truck is done.

Denny, I did run it for a couple hours this afternoon and no change that I could notice.

Jeff, that is a good idea. I was moving the slider all the way home for the test. I will try slightly off home position and see if it helps.

Mark

Update, I tried the vacuum test with the slider in various positions near the home position, and it is all the same, no matter the position. I have about decided to use it like it is. The leak is very small of course and worst case I will have to adjust the idle jets a bit. Off idle it won't be noticed.

Also I should clarify, all this is not meant to be critical of Wiperman or his work and service to our hobby. I am just trying to find out if this leakage is normal for a rebuilt motor.

Thank you for all the comments.

Mark

I have a big box of old wiper motors and half of them hiss at the on/off switch. If the casting under the on/off slide is worn, I don't think it can be fixed. Wiperman should be able to answer this.