C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

72 Wiper Door Linkage

Old 04-25-2019, 09:52 AM
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Default 72 Wiper Door Linkage

I've been troubleshooting some wiper door vacuum issues on my 72. I've traced some leaks to a faulty wiper arm vacuum switch (which i replaced with a Wilcox one) and a slight leak on the wiper diaphragm actuator. I have verified that the switch and wiper override vacuum switch work as they should, and the diaphragm works in both directions when not hooked up to the wiper door linkage, but it doesn't have enough force to open or close the door. If i have vacuum on one side of the diaphragm i can feel it pulling through the other side so I know it is leaking slightly.

Do i need a perfect seal on the diaphragm to operate the door? How much resistance is normal to manually operate the linkage? I'm going to throw some silicone grease on the pivots to see if that loosens it up a bit, but is there anything else I should be looking for? Is the spring on the linkage arm (circled below) an open or close assist, or just a flexible joint?


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Old 04-26-2019, 12:00 AM
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There are many points of failures or weaknesses on the vac system. Also many of the newer aftermarket parts can also fail right out of the box. I know the headlight actuators look nice but have a heavier spring inside which requires more vacuum to make them lift and close. The expansion tank is another one that requires just a small amount of air pressure to find a leak. One guy at one of the NCRS meets mentioned that he was using loctite on all his line connections and having great result. Hard to tell when he try's to pull one off though.

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Old 04-26-2019, 12:43 AM
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If you have identified a leak in the diaphragm inside the actuator then that is your problem. You can replace the outer seals on both ends easily but not the diaphragm. Unlike the outer seals on the actuator, It only takes a slight pin hole leak on that diaphragm to slow it down or stop it from working at all. Are you sure it's the diaphragm and not the front or rear seal leaking? If the diaphragm, you need a new actuator. The outer seals are easy to replace and cheap.

Last edited by CanadaGrant; 04-26-2019 at 12:46 AM.
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Old 04-26-2019, 09:18 AM
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If I put vacuum to one side of the diaphragm itll pull it to that side but builds vacuum on the other side when i block it, so there is definitely a leak through it. I ordered a replacement from Willcox, hopefully that solves it
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