Any thoughts on where I should look first? Vacuum tank repaired, all new vacuum hoses, wiper door actuator and vacuum control valve were purchased new. Linkage assembly was bought totally refurbished and I lubricant linkage assembly twice. With help from my hand it will fully open but seems like something is binding. The door will slams shut. The wiper door override below the steering wheel has the same lackluster effect on the opening of the wiper door. Could it be adjusting the amount of wiper door linkage shims? Could it be any other adjustments that I’m not aware of.

 

did you test the actuator and vacuum control valves before putting them in?? heard the new ones don't always hold vacuum...

/jc

 

I will try those first. Thank you for the reply.
Jeff

 

Without the vacuum actuator fitted how smooth is the operation if you push/pull the actuator linkage by hand.

 

I have a hand held vacuum pump and gauge. I think it's called Mighty Vac (or something like that). Connect it directly to the big pot vacuum canister that extends and retracts the door. See how it moves in response to the vacuum indicated on the gauge.
.............
Another line of attack. Get some "dry" graphite lubricant used to lubricate key mechanisms. It's powdered graphite mixed with a highly evaporative liquid solvent. Put drops of this stuff on each the plastic sleeve bearing joint pieces. The liquid carries graphite particles into the joints and then evaporates leaving the joints greaseless but now with graphite particles in the joints for lubrication. This should make the door open/shut mechanism easier to open and close. Don't want to use a light oil for lubrication since it'll eventually attract dirt particles.

 

Hello,
Perhaps the long 'nut' that joins the actuator's rod to the linkage rod need's to be adjusted so the 'stroke' is a bit longer?
Maybe?
Regards....

 

I removed the green and red vacuum lines from the actuator and the rubber circular plug from the red side. I then inserted a screwdriver and pushed on the metallic diaphragm and the door seemed to operate into the fully open position without any binding. I removed the actuator from the car and checked the red and the green connections with vacuum and I thought I found my problem.Good thing I double checked because my hand pump is trash. If I put my finger over the red or green ports and push or pull on the actuator rod it holds which I believe indicates that the actuator is good.

I tried to adjust the actuator rod length but after I reinstalled everything my wiper door still will not fully open without some help. The door does slam shut.

I also had a problem with the wipers not coming on unless I wiggled the wiper arms but I believe I fixed that problem by adjusting the electronic wiper micro switch plunger. The wipers will park and the door will slam shut.

It seems liken there is not enough vacuum being applied to the green side of the actuator. Thinking about applying my electric Harbor Freight vacuum pump tomorrow to the green side of the actuator to see if it fully opens the wiper door.

I will be ordering a new vacuum hand pump this evening to trouble shoot the actuator and the relay.

My second thought is that the relay could possible be bad but it is located in a really tight location. Looks like removing the side egg crate side grill maybe the way to go with its removal

 

You can test your theory easily then by simply removing the hose that closes the door and connecting it to the green side of the actuator.
Remove both hoses and simply move the "good"/Red hose from one side of the actuator to the other. If you get full open/close via this method then you know your actuator, the linkage, and the red side is working.

 

Thank you Alan, i will also try that in the morning. Just returned home with a new hand held vacuum/pressure pump for component testing.

 

Trouble shot the vacuum actuator, and it looks to be working. Lengthened the long coupling with the left-hand threads and the thread length of the actuator shaft.
Relubricated all the movable joints on the linkage with graphite as suggested. I purchase this linkage fully restored from eBay if I remember correctly and believe I paid $900.00 for it. Too long to remember, going into the 9th year of this restoration.
I also swapped the red hose to the green hose positions, on the actuator and the door still only opens halfway and fully if you give it a slight push.
Also hooked up a manual vacuum pump to the green side of the actuator and the door does not fully open without some help.
I did not remove the wiper door vacuum relay and suspect that it is working. I'm ruling that out due to the fact that I'm having the same results with the door not fully opening when I use the hand vacuum pump.


It seems to me that the linkage must be binding somewhere. I also noticed that the right-hand machined shaft bolt which fastens the door to the linkage was really loose.so, I tightened it up but still have the same problem.
I
Any thoughts on where I should start to trouble shoot the linkage for mechanical binding?

I hate to have to that the wiper door off, what pain in the *** getting those 4 machined bolts back in that attach the door to the linkage.

There are two "L" shaped brackets, one on each side that secures the linkage to the face of the windshield firewall,.could these need to be adjusted?

Could the linkage need to have more or less shims where it bolts through the firewall?

Any suggestions would help or the name of someone that specializes in linkage restoration, to pick their brain.

Respectfully,
Jeff

 

The shims on the brackets between the linkage and the firewall basically adjust the wiper cover distance between the glass and grill behind the hood. I suppose that if the difference in shims was extreme it would cause binding in the linkage, but then the distance of the cover and the glass would probably be noticeable. Have you measured the amount of vacuum at the vacuum tank (not engine vacuum), after the filter and check valve. Slight chance that you have a restriction there. You should have the two pie-pan cover actuator. Have you removed it and tried to operate the mechanism by hand? I think you would need a fairly long screw to connect to the mechanism so that the pie-pan linkage does not fall inside of the chamber. You can get it back out but it is easier to operate if you can operate with a longer screw. You should be able to operate it fairly easily by hand in both directions. The cover should not slam closed. Has it ever worked? You mention that you bought the linkage refurbished. I redid mine and it is possible when putting it back together to easily do it incorrectly. I took pictures of mine before I replaced all of the rivets and bushings, so if you get to the place of removing the assembly I have a picture of how it should be assembled.
Here is a vacuum hose diagram (made for my 69), but the basics are the same. I think you have two relays for the headlights and your wiper door relay is not up by the master cylinder, but mounted down in the passenger side.
There is also a wiper arm valve that stop the cover from closing until the wiper arm presses on it. These tend to be problematic sometimes. It doesn't stop the cover from opening. The whole cover system is a strange mechanism, it looks good that you can't see the wipers and the cover keep the sun off of the blades, so that they last longer, but it can be a pain to get everything to work correctly.

 

Thank you for your detailed response and the drawing. I remove and reversed the red and green hoses at the actuator. I get the same sluggish response from the door. It will open half way and all the way with a push from my hand. I also applied my brand new hand held vacuum pump to the green side of the actuator and it still only opens half way. If my thinking is correct I believe the distance between the actuator threaded end and the left handed threaded rod coupling needs to be as long as possible for the longer stroke which makes sense. I have not tried to make this distance as short as possible, but that thinking does not make sense to me.
With the actuator disconnected I can grab the door and move it back and forth. There is no blatant binding but maybe just enough to prevent the door from fully opening under vacuum.
I will be loosening the four pivot bolts that attach the door to the linkage and try to re-lubricate them with white lithium grease. May be there is not enough lubrication on these nylon bushings to let the door open free enough.
I do have another linkage assembly, that I know was never been molested, for reference.

I also ordered a vacuum gauge last night to check vacuum values.
Jeff L.

 

Pull a Vacuum on the canister and see if it holds, If it doesn't the front seal is leaking. I just had the same issue on my 71.

Loosen the mechanism to car mounting screws slightly and try it again . Only do this a few times, keep an eye on the screws, they like to fall out.

If no good loosen the door screws slightly and try it again loose, Again only a few times .

If it works tighten the screws one at a time.

A friend painted his door and the thick paint caused the binding. Took me a little while to figure it out.

Good luck, it's a PIA but worth it.

 

“Mechanism to car mounting screws”. Are these the nuts on the threaded studs that mount the linkage to the firewall, located on the engine bay side that you speak of? I will try to loosen the reduced shank bolts that mount the wiper door to the linkage as you suggest.

Thank you.

 

yes, mechanism mounting screws, sometimes you can "****" the mechanism and it jams.

When I'm working on the wiper door, I put rags or paper towels in the sides to stop things from dropping into the fenders.

A few times on friends cars I have had to remove the wiper door and operated the mechanism by hand from the canister point (after removing the canister) to see which side is binding, Painting the mechanism is ok, but then you should clean and lube the pivot points which they did not do.

 

Figured out my problem and I’m drinking right now! As I stated the wiper door linkage that I installed in my 9 year restoration was purchased as refurbished linkage off eBay years ago. I saved the original linkage when I removed it during the disassembly. After manipulation of the wiper door we could see that the spring mounted over the main linkage shaft would twist rather than coil around the main shaft. After further investigation it looks like there should be a sleeve or bushing in between the main shaft and the spring in order to let it coil while the vacuum actuator starts the opening operation. I believe the actuator has only a certain amount of throw before the coiled spring takes over and fully opens or closes the wiper door. I refurbished the original linkage and just completed the swap out. I now have everything installed, adjusted and operating correctly including the best gaps and height alignment that I believe is possible. Talk about geometry. The engineers at GM that designed this system were definitely on their game!

 

Good job on finding that binding spring. When I rebuilt my mechanics and replaced the rivets, I did not mess with the spring. I don't think that I have ever seen a silver car with that much shine. It looks very good. The wiper cover looks slightly misaligned on the passenger side. The shims where the assembly mounts to the firewall make the alignment to the windshield. The is also a screw with a nut that the assembly presses against in the closed position. If you haven't adjusted this, perhaps it is sitting a little high.
Here is the adjustment for that screw from the 1969 AIM, but that part or the car is identical. Here is a picture of my car as an example. My hood is blocked slightly open to allow air to escape after I turn the engine off.

 

Hello,
Silver with RED!!!!
What a terrific combination!
What a terrific car!!!
Regards...

 

Performed a lot of work on this 1971 coupe over the last 9 years. Probably upside down with the investment but i love corvettes and the challenge of restoration. Replace a large amount of the frame and 3/4 of the birdcage. A numbers matching car delivered to a Chevrolet dealership in Ontario Canada. A nut and bolt body off restoration. I did not rebuild the motor, differential or the transmission. I also did not paint the car but I did remove the front clip, birdcage and replaced the right rear fender. I did perform the remainder of the restoration work including the reinstallation of the birdcage, front clip including electrical harness. The biggest challenge was

Sitting at my office in NJ the day it was delivered.

Frankenstein!

Pictures taking in Pennsylvania the day i purchased the car.

More pictures from Pennsylvania.

Pennsylvania

Pennsylvania

Body lift.

Delivery to my office.

Frame sandblasting and paint.

New section of birdcage in place.

My brother lending a hand.

New NOS fender installed.

Drive train.

Drive train.

Friend Vinny leaning a hand.

Restored storage bin.

Front clip reinstalled.

Oh boy!

Working the gaps.

Console restored.

Recovered seats.
trying to perform perfection where perfection never existed before.