Vacuum Windshield Wiper Motor Troubleshooting

[rp2813]

Hey guys,

Since we've got a vintage car thread going here, I figure it might be a good time to inquire about repairing vacuum wiper motors. Specifically, the Trico on my '50 GMC pick-up. Right now the wipers will make the first half of their sweep, upward and outward to the edge of the glass, but they won't come back down unless I shut them off.

I pulled the motor apart and it was really gummed up inside and all over the paddle. I cleaned it all up, re-installed it and there was no change. I also replaced the vacuum hose in case the hardened old one had any leaks. No help. I found something on line for a Trico motor on a '37 Plymouth. Basically the same thing and it had some tips for oiling, which I haven't tried yet. My back is sore from contorting under the dash this last round, so I'll wait until I have something else to try before pulling the motor out again.

Is there any way to determine if the motor simply needs to be replaced? I don't want to buy a new one if the original simply needs some TLC to start working properly again.

Any help or suggestions would be appreciated.

Thanks,

Ralph

 

[58limited]

If oiling doesn't work, there are outfits that restore them listed in Hemmings motor news. Ebay is also a good source.

 

[qsd-dan]

I have never ventured into vacuum type wiper motors, but I would imagine there's a vacuum diaphragm in there. Have you tired pulling a vacuum on it and seeing if the diaphragm holds vacuum overtime?

 

[rp2813]

Yeah, I haven't yet found an exploded view of a motor to determine if there's a diaphragm and where it would be. Even the truck's shop manual doesn't go into it much for motor repair and suggests replacement, but since it's got screws instead of rivets holding it together, I see no reason not to try and fix what I have.

I know we still need rain around here, but we've had a wet January and it would be nice to have a bit of a break. Getting the wipers working properly would be one way to make that happen ;-)

 

[58limited]

If you are interested, there are electric upgrades available in the restoration catalogs. I have one on my '53 Chevy truck.

 

[ironrite]

This may help

My last car that had vacuum wipers was a 1960 Lincoln Continental. There was a vacuum line that went into a large can. Picture a large vegetable juice can. Another line from the can then branched out to the various vacuum feeds, like door locks and A/C controls. I suspect the can was to even out the vacuum variations from the engine. The Lincoln, if my memory serves me, had a separate vacuum pump in the motor, tied into the oil pump as the line for this can went down to the side of the engine block.

This might help if it is not a switch or the wiper motor problem. My dad's 1969 LTD also had this same can thing for the vacuum supply for the A/C and the hideaway headlights.

 

[qsd-dan]

Yeah, if the wiper motor is hooked up to a series of other vacuum lines that branch out everywhere, try hooking up the vacuum line to a direct manifold vacuum source.

A poor mans way of testing a vacuum diaphragm (if a vacuum pump isn't available) is sucking on the vacuum hose and putting your tongue over the hose once enough vacuum has been pulled. Wait at least a full minute and note any loss of vacuum. Properly functioning vacuum diaphragms should hold perfect vacuum indefinitely.

 

[rp2813]

The system on the pick-up is very basic and a lot less complicated than the Lincoln and Ford systems described above. It's a direct line from the manifold.

Dan, your method is easy enough to try with the motor still in place, and could save me a lot of time and trouble.

I don't know if an electric upgrade would work for my truck. It's all original and still has the 6-volt positive ground system.

 

[athanasius80]

The die cast housings are known to wear out from use and or warp with age. Perhaps a rebuild from one of the professional guys is in order?

 

[sudsmaster]

I fixed the vacuum wipers on my '50 Plymouth about 16 years ago.

I got an NOS unit from an outfit I found on Hemmings. They will also sell you a rebuilt kit for less if you send them your "core".

I also took apart the one that came with the car. It wasn't gummed up but the rubber on the paddle appeared to be damaged (as I recall). I think there is also valving involved, which shunts the vacuum from one side of the paddle to the other to get the reciprocating action.

I still have the original unit but it's no good for any practical purpose without a rebuild.

It seemed to me the big enemy of these motors is heat. The old rubber dries out and then doesn't seal any more. At least that's what I thought when I took it apart.

You could remove the motor from under the dash and test it connected directly to the vacuum line from the intake manifold. Be careful; the motor can be surprisingly powerful and even the short lever attached could pinch a finger pretty bad.

 

[rp2813]

Thanks Rich

I think from what you've described, my motor is beyond shot. It's probably the valving you mentioned, combined with compromised paddle rubber. I'll go on line and see if I can find a rebuild kit/core exchange offer, unless NOS isn't too much more expensive.

There's no point in removing the motor to test it on the vacuum line because it's already attached to a direct line into the manifold. I think it's toast.

Thanks for all the input and advice here. I think it's replacement time.

 

[sudsmaster]

Ralph,

On re-reading my post, I see that I used the wrong words to describe the service I found way back when. The outfit would sell either a NOS unit or a rebuilt unit, not a rebuild kit. I opted for the NOS unit since it wasn't that much more than the rebuilt unit, and I wanted to keep the original in case I wanted to get that one rebuilt later on. But so far the one I put in 16 years ago is still working well. I think keeping the car garaged and out of the sun helps ;-).

I have to say I find the vacuum wipers to be very entertaining in action. The Plymouth has a vacuum pump booster that works off the camshaft (it's on top of the fuel pump). I'm not convinced it does all that much, although I did rebuild it way back when. In any case, the wipers speed up when the car decelerates and slow down when the car accelerates. Keeping them steady during stop and go driving can require constant attention to the little control on top of the dash. At least there's nothing to short out ;-)...

 

[spankomatic]

I have to say I find the vacuum wipers to be very entertaini

I love to be entertained. Video ???

 

[qsd-dan]

All of this vacuum operated wiper motor banter reminds me of the late 90's, being in my buddy's Cadillac, rain pouring down in buckets, going up the Altamont pass......and the bloody wipers damn near come to a halt due to the loss of engine vac. Talk about an "Oh Shit" moment!!

 

[rp2813]

It amazes me that vacuum wiper systems were used by some manufacturers well after more reliable electric motors had proven themselves. Ramblers had vacuum wipers well into the 1960's.

It has always been the case with the Jimmy that the wipers would nearly fly off the windshield upon decelleration and would come to a dead stop once you hit the gas again. While cruising along during just a moderate downpour it's routine to have to let up on the gas pedal to get a fast swipe if the wipers are moving too slowly. Rich, you are absolutely right about having to constantly fiddle with the control knob.

I'm going to try the oiling trick I found for the 1930's Plymouth wiper motor and see if that helps before pursuing a NOS/rebuilt unit or sending mine off for its own rebuild. It seems kits are impossible to find so labor costs are pretty much unavoidable.

 

[sudsmaster]

Funny this should come up...

I'm taking an automatic transmission night class at the local community college. I was bringing in my '78 Dodge long bed in Thursday night to check out the leaky transmission, change the gasket & filter, and maybe adjust the bands.

Well, I got about 5 minutes away from home and as I pulled up to a stop light, the wipers died (it was raining lightly). Since a big storm was predicted I decided to go back home and get my other vehicle.

It doesn't seem to be the motor - I can still hear it going when I turn it on. Probably the linkage, somewhere. I'll be looking at it tomorrow.

 

[ironrite]

Vacuum Systems Still Used

Ralph, was surprised when I bought a 1997 Mercedes C280 about a year ago. Vacuum door locks and trunk release. Though they are run off of a electric/vacuum pump. According to my mechanic, Mercedes still uses the vacuum system in their new cars. It does give a nice little whoosh sound when I hit the locks on the car. Reminds me of my old Lincolns. It has one of those single wiper things that can be a pain to fix as well. Electric operated, but uses a cam system that needs attention from time to time to keep working right.

 

[whirlaway]

Electric!!!!!

You might want to try a junk yard.Look for a smaller body pontiac and chevy from 46 to 54 and see if you can find one with electric wipers,should hook right up.I do know Chrysler products from 41 to 52 should fit a Plymouth.Electric wipers were standard on Chrysler,Desoto and Dodge from 41on up.2 speed at that.All of the models I have owned had electrics.They are much safer.The vacuum can on Gm and packards was used to hold constant vacuum on the wipers.Those old GMs had that awful cable system on the bigger models til at least 59. Thanks Bobby Oh yeah I forgot the 1st 55 Chevy and GMC models might have had an electric option,Early 55 the truck did a major redesign.

 

[sudsmaster]

Found out the problem with the '78 Dodge truck wipers.

One of the four plastic bushings/couplers on the linkage under the cowl vent had disintegrated and let go. I struggled for a while to try to fit an o-ring and e-clip to fashion a repair. Then I hit the internet and found that a local Napa store had replacements. They didn't have enough to redo all the grommets; I'll probably order these on-line for a later upgrade.