The door pops up a little when I shut it off. When I start it up, closes immediately. What should be replaced? Thanks for the help!

 

You have a vacuum leak. Time to buy a Mity-Vac and vacuum diagram and start tracking the leak. It's very easy to do, but takes some time. I always plug the headlight side of the system (and vice versa) when working on the wipers as it removes half the possible problems from the system.

Lots of troubleshooting guides on-line and plenty of help in the forum.

 

The most common problem when this happens is the vacuum wiper arm switch under the hood grille.
So... I'd test this first.

http://repairs.willcoxcorvette.com/1...m-switch-test/

If you need one, I'm the only person in the country that makes one that works properly.
https://willcoxcorvette.com/corvette...t-really-works

Willcox

 

I would first replace the metal vacuum check valve; it is the second component attached to the primary vacuum feed line coming from the intake manifold. There is one fitting on the IN side and two fittings on the OUT side. That device must seal well to retain vacuum in the reservoir tank when the engine is turned OFF. If yours is the original valve, it's probably overdue for replacement, anyway.

It would be a good idea to replace the plastic filter which is also in that same primary vacuum line.

 

This is what cured my wiper door. Same symptoms

 

Same with my wiper door opening on shut down ,don't buy the cheapo wiper arm safety switch Chinese ones .You will be buying the usa one in the end any way .Here is how to set it up

 

replace the pull down switch under the steering column

 

Thanks for all of your help! Here’s what I have found. The door switch has been tested and works per the video, I replaced the check valve and found that the new filter leaks and and temporarily eliminated it until I can get a new one. Also replaced all of the vacuum lines to the wipers controls under the hood. It still pops up slightly.

Should this be my next move? http://www.71corvette.com/wiper.html

Thanks again for your help!

 

When I replaced my switch, I had to ensure the wiper blade was making enough contact with the switch. I had to adjust it’s position (switch) to make it so

 

I'm not sure the wiper door solenoid is your issue, but I repaired mine recently which was fairly easy to do. The challenge is getting at it and putting it back in. I removed the drivers seat to gain better access.

 

Thanks, I’ll give it a try.

 

Ok, I adjusted the vacuum wiper arm switch and it still does the same. Do you think I got a bad check valve? How do you test to see if it works properly?

 

Boy, I'm workin' the brain cells hard, here! Years ago, I had the same issue and trying to think back, I'm pretty sure that the problem turned out to be a small 'clog' in the metal vacuum transfer pipe running across the firewall. About halfway across, the pipe takes a dip downward. Over the years of use, condensation, dust, etc, a bit of a clog developed.

I removed the rubber vacuum lines from each end and connected a 'clean' hose to one end and tried to blow thru it. Nothing. Fired up the compressor and blew some pressurized air thru it. Voila'!! Reconnected the original vacuum lines and the wiper door no longer had the problem. I know that has been at least 10 years ago--no issue since.

Hope that works for you, too.

 

You can keep throwing parts at the problem or simply use a Mity-Vac and track down the leak in a couple of hours as I originally suggested.

If you are going to keep throwing parts at the problem a bad vacuum relay can also cause the issue. Ditto the solenoid mounted behind the tack which are also known to leak. Ditto the wiper door actuator.

Also a leak on the headlight side of vacuum system can cause the wiper door to pop up. Plug the headlight side of the system with golf tees to and see if you still have the problem as that will eliminate numerous possibilities. A leaking storage tank could also cause the problem.

The are two types of C3 owners in the world... those that own a Mity-Vac and those that will own a Mity-Vac.

Good luck.

 

Is a 1968 much different to this? I have the same problem

 

#1 These parts are relatively cheap, so you're not killin' your wallet by replacing parts that are way beyond their usable life, anyway.

Also, blowing thru metal tubing is more 'cost effective' than "throwing money at" a Miti-Vac, I think. Nothing wrong with that device.....if you need it. I guess, more tools is always better!

 

Clone Mity-Vac's are $15 at Harbour Freight or on Ebay, the real deal is only twice that, so it's not like tracking and fixing the problem correctly is going to break the bank. Not to mention if you own a 50 year old C3 this will not be the last time in your life you're going to have to deal with a vacuum leak.

Or as my dad always told me... "There is a big difference between being a good mechanic and being a parts changer..."

YMMV

 

I have three pumps, I was looking for advice as I can’t find anything under the hood and have had the dash apart 3 times and didn’t want to again if I didn’t need to.

 

So start from the offending end first - in this case the vacuum actuator that opens/closes the wiper door, Its important to remember that the vacuum system
will fail on the side of safety; i.e. it will open if there is no vacuum. While troubleshooting remember that green lines open, red line close, and yellow lines supply vacuum and white line are the control lines. So with that in mind:

1. Take the red line off the wiper door vacuum actuator that opens/closes the wiper door (On passenger side above heater). Put your vacuum ( I read you had 3?) pump on this end,lets see what happens when you run the car (should see vacuum here if the wipers are off). Now turn the car off - what happens - do you see the vacuum needle slowly swing down or does it stay constant?

2. If it slowly goes down, you can then move on to the vacuum relay unit on the drivers side under the hood. You can test the white control line here (it's fed from the wiper arm position valve). Pull it off at the valve end and put your vacuum meter here. It should show vacuum if the wipers are off and the car is running AND it should hold that vacuum when the car is shut off - does this work correctly? The white control line's vacuum will allow the yellow line's vacuum supply (from the vacuum canister) to be ported to the red line that feeds your wiper door actuator. Does this all check out?