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A vacuum wiper motor question
#980301 Tue Oct 22 2013 02:56 AM
Joined: Dec 2005
Posts: 409
M
Shop Shark
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

Re: A vacuum wiper motor question
Mar-Ktech #980370 Tue Oct 22 2013 12:41 PM
Joined: Mar 2002
Posts: 9,066
Master Gabster
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.


1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!
Re: A vacuum wiper motor question
Mar-Ktech #980371 Tue Oct 22 2013 12:45 PM
Joined: Oct 2006
Posts: 11,766
D
Extreme Gabster
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

Last edited by Denny Graham; Tue Oct 22 2013 12:55 PM.
Re: A vacuum wiper motor question
Denny Graham #980410 Tue Oct 22 2013 02:43 PM
Joined: Dec 2005
Posts: 409
M
Shop Shark
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

Last edited by Mar-Ktech; Tue Oct 22 2013 03:49 PM.
Re: A vacuum wiper motor question
Mar-Ktech #980431 Tue Oct 22 2013 04:11 PM
Joined: Oct 2006
Posts: 11,766
D
Extreme Gabster
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

Re: A vacuum wiper motor question
Mar-Ktech #980455 Tue Oct 22 2013 06:19 PM
Joined: Mar 2002
Posts: 9,066
Master Gabster
I don't believe the valve in question relies on the seal of the flapper.



1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!
Re: A vacuum wiper motor question
Mar-Ktech #980473 Tue Oct 22 2013 07:18 PM
Joined: Oct 2006
Posts: 11,766
D
Extreme Gabster
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

Re: A vacuum wiper motor question
Mar-Ktech #980510 Tue Oct 22 2013 09:33 PM
Joined: Sep 2013
Posts: 19
1
New Guy
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


1956 GMC 102
1952 Chevy hardtop
1932 plymouth PB 3 window coupe
1980 H-D FXWG
Re: A vacuum wiper motor question
18inchapes #980521 Tue Oct 22 2013 10:05 PM
Joined: Dec 2005
Posts: 409
M
Shop Shark
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

Re: A vacuum wiper motor question
Mar-Ktech #980641 Wed Oct 23 2013 04:20 AM
Joined: Dec 2005
Posts: 409
M
Shop Shark
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


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