Vacuum Wiper problem

[checker]

I have a 1950s type Trico vacuum motor on my car that I can't seem to get to operate my wipers. One or two sweeps per minute is all it will do. I read up on the oiling of the motor yesterday, pulled it out and oiled it. It's actually a new (perhaps NOS) motor that has no use. The unit operates smoothly and there is 20" pounds of vacuum on the hose at idle. What I learned tonight is the motor and linkage operate perfectly back and forth on the car, but when I put the arms and blades on, the wiper motor can't seem to overcome the drag across the windshield. New vacuum assist fuel pump is also installed. Any suggestions would be appreciated.

Doug

[61polara]

If the windshield is dry, that will cause vacuum wipers to run slow. Try running them with a wet windshield and let us know how they run.

[Owen_Dyneto]

What did you oil the motor with? Hopefully not motor oil which will degrade the paddle seal. Use vacuum motor oil, or perhaps a silicone oil. Also possible the resistance is in the linkage system and not the motor itself.

[checker]

I used a very thin weight silicone oil. I was not going to try brake fluid because of paint concerns.

[NTX5467]

Key thing is probably NOT the type of oil, as I seem to recall "chassis grease" getting dry and then liquefied by a dab of brake fluid (by a member of our Buick club chapter on his '58 Super), but just how well the seal is between the paddle and the housing. I'd also make sure the linkage is well-lubed at all pivot points, plus the "stand-offs" the linkage sticks through where the wiper arms attach to it. As mentioned, the dry windshield can be "a drag" on things, but I seem to recall that our '51 GMC (when it was still being used daily, in the '60s) would still move the wipers on a dry windshield, just slower. Without the booster fuel pump, engine load did affect how fast they worked.

Just some thoughts,

NTX5467

[checker]

Thanks all for your replies.

61polara, as luck would have it my car got caught in the rain today. I was thrilled when the wipers quickly sweep across the windshield and also thought the dry drag was perhaps the issues but that notion was shortly lived because next time I turned them, and it was still raining, they struggled to move.

NTX5467, I was thinking the same as what you stated concerning linkage. Without a doubt all pivot points are dry so I will lube them in a few days. Too cold and wet currently.

[Spinneyhill]

Remember that oil is a wetting agent and will attract dust, clogging up the connections in the linkages. Grease is better for this purpose, but a "dry" lubricant is even better. Silicon is good, but not graphite (galvanic corrosion will follow).

[Curti]

I suggest removing the wiper motor and completely dismantle it. Take care when disassembling the kicker valve, it will only work one way upon reassembly. Clean the inside of the bowl and the paddle. Squirt brake cleaner with the small diameter tube through every hole in the top cover. Take care to preserve the gaskets. If you ruin them, they are available. Pack the center of the paddle with wheel bearing grease and lightly grease all of the surface on the inside of the bowl. I have successfully rebuilt many old 30's Trico motors.

[checker]

thanks all. This weekend I plan to great the linkages.

[Owen_Dyneto]

I really recommend you not use wheel bearing grease inside the motor, as has been suggested. What differentiates vacuum motor oils is the absence of lighter and more volatile components; under vacuum these lighter fractions will gradually be taken off by the vacuum and the remainder will gradually become more viscous, eventually like a gum or sludge. Stick with vacuum motor oil or in the absence of that, light silicone grease.