I have a 1972 Corvette and the wiper door opens then closes right after starting it. I was wondering what may be the cause of that? I have checked for vacuum leaks and couldn't find anything. Sometimes it will also gradually open after shutting the vehicle off. If anyone has any suggestions it would be greatly appreciated.
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Re: 1972 wiper door problems
If there truly are NO leaks in your vacuum system, then check the routine maintenance items...
(1) The in-line filter (white plastic, plastic dual pie pan shaped) was intended to be replaced once a year. When the filter element is clogged, it restricts air flow through the system and can allow the servo side of the vac system to come up before the control side of the system (winking headlights, twiching wiper door).
It's installed just after the intake manifold vac nipple, in-line, with the primary vac hose. Pull it, hold it to the light and look through. If you see clean white gauze, you're good to go. If it's black as a coal mine, you've not done proper maintenance and you need to replace it. If you can see straight through, you've gone too long between filter replacements and guess what happened to the internal filter element? Yep, she was sucked into the intake and down through the combustion chambers...
(2) The in-line check valve (grey metal, dual pie pan shaped) is worn out and the internal rubber umbrella valves aren't holding pressure. One side connects to the main vac hose down stream from the vac filter. The other side has two nipples with the smaller feeding the vac control side of the system and the other (larger) routing to the vac storage reservoir that supplies the system's servo side.
Testing is easy. Remove the check valve, plug one of the outlets from the dual nipple side and gently suck + blow. The valve should let air move in one direction and NOT the other. Then, plug the opposite side of the valve and verify that segment...
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