72 Windshiled Header repair

[Patrick H.]

...and yes I know how to spell Windshield but you can't edit the thread titles...


Hello All,

I had a chance yesterday to remove the stainless trim from the top and from of the windshield header on the 72 I'm working on. As an FYI you can reference the previous thread: https://www.forums.ncrs.org/showthre...66381&uid=4845

After removing the trim I vacuumed up the rust I saw and used an awl to pick away any scale. Thankfully it does not appear as bad as I thought it would. The driver's side is absolutely perfect. Here is a picture of the passenger's side, with the center of the car on the right side of the picture:



Some surface rust near the middle T-bar:



Right outer corner rust:



Underneath that same corner:



The worst rust is under the right front corner. I scraped it and picked at it, and then used the awl to try and poke through it from above and from below. I am not able to punch through the rust.

At this point since I do not seem to be able to show a loss of structural integrity I am tempted to remove as much rust as possible, paint it with Eastwood's rust paint, caulk and reassemble. I am not sure that I will gain much by removing the chromed right upper corner piece and investigating.

Does anyone else have thoughts on this?

Thanks,
Patrick

[Jim T.]

Re: 72 Windshiled Header repair

Are you going to remove the windshield and do the rust preventive measures also?
On the drivers side and passenger side lower corner below the windshield frame there is a piece of fiberglass that is attached to the steel birdcage. This fiberglass piece provides support for the top of the fender.
Directly underneath the fiberglass support as mounted there is a open round hole just over an inch in diameter in the steel birdcage. When new the fiberglass fender support could of done a reasonable job of preventing water from getting underneath the fiberglass support.
Things happen, and water can migrate into the hole in the birdcage. This area of the birdcage is a double wall of steel so you cannot see the hole to inspect it for actual leaking from the inside to see if water is getting into a C3 from this access.
If you wash your car or is in the rain and you have water that appears on your floor mats on on your leg it can come from this hole in the birdcage.
Why this hole is manufactured in this piece of the C3's birdcage when it is assembled in a drain area of water coming off the windshield I have no idea.
The replacement pieces of the birdcage, a double walled steel piece, bought new by me in 1986 from GM even had the hole. I welded a steel cover over them before I installed them.
These holes in the birdcage steel when discovered explained why I was getting some drippings of water on the the floormats of my 70 that migrated along the bottom of the dash to drip from.

[Tom L.]

Re: 72 Windshiled Header repair

Jim is correct, I did not do the restoration on my car but windshield removal showed basically the same problems he described. These included the frame, Hidden by the windshield, headder and the part under the fiberglass piece that supports the left front fender. All of which were repaired at an expense that was reasonable compared to leaving the damage and allowing it to fester.

[Patrick H.]

Re: 72 Windshiled Header repair

Are you going to remove the windshield and do the rust preventive measures also?
On the drivers side and passenger side lower corner below the windshield frame there is a piece of fiberglass that is attached to the steel birdcage. This fiberglass piece provides support for the top of the fender.
Directly underneath the fiberglass support as mounted there is a open round hole just over an inch in diameter in the steel birdcage. When new the fiberglass fender support could of done a reasonable job of preventing water from getting underneath the fiberglass support.
Things happen, and water can migrate into the hole in the birdcage. This area of the birdcage is a double wall of steel so you cannot see the hole to inspect it for actual leaking from the inside to see if water is getting into a C3 from this access.
If you wash your car or is in the rain and you have water that appears on your floor mats on on your leg it can come from this hole in the birdcage.
Why this hole is manufactured in this piece of the C3's birdcage when it is assembled in a drain area of water coming off the windshield I have no idea.
The replacement pieces of the birdcage, a double walled steel piece, bought new by me in 1986 from GM even had the hole. I welded a steel cover over them before I installed them.
These holes in the birdcage steel when discovered explained why I was getting some drippings of water on the the floormats of my 70 that migrated along the bottom of the dash to drip from.

Any pictures which approximate where this hole might be?

I had not planned on removing anything beyond what you see unless I find a compelling reason to do so. I am not completely restoring the car, just making it roadworthy after 15 years in a barn. Generally speaking I am amazed by the lack of rust on many items of the birdcage and other pieces of the car. However, the owner wants to do what we need to do to fix it.

[Pete B.]

Re: 72 Windshiled Header repair

Jim if I understand you correctly is this the hole that is only visable when the speedo and the right hand side lower dash panel is removed? On the left and right hand side. Are these the holes that you "closed up" I'm very curious as I am right at this point and have some rust on my driver side. I am doing a body off and see that at one time the water had run through into the inside of the car. Thankfully my birdcage is sound also. But I dont want it to get any worse.

Any pictures which approximate where this hole might be?

I had not planned on removing anything beyond what you see unless I find a compelling reason to do so. I am not completely restoring the car, just making it roadworthy after 15 years in a barn. Generally speaking I am amazed by the lack of rust on many items of the birdcage and other pieces of the car. However, the owner wants to do what we need to do to fix it.

[Jim T.]

Re: 72 Windshiled Header repair

Pete the hole is not visible from inside the car. What you can see from inside the car is the inside/underside of the double wall of this birdcage frame.
If a person wanted to seal the hole on the outside of this double wall birdcage piece a way to do it without doing what would have to be done from the topside is this. A hole cutter could be used on the inside double wall of the birdcage frame to cut a hole and a patch piece applied through the cut hole to cover the hole in the birdcage frame and stop the water leak. Then the inner birdcage frame cut hole could be closed.

Patrick I have a lot of pictures of all the damaged areas of my 70. I had never done any restoration work like I encountered and took lots of pictures. My pictures are prints from 1986/87. Wish they could of been taken with a digital camera so I could learn to post them like yours.

Another option is to seal around the fiberglass attached fender support to stop the leakage. However the location is pretty much unaccessable.

[Patrick H.]

Re: 72 Windshiled Header repair

Pete the hole is not visible from inside the car. What you can see from inside the car is the inside/underside of the double wall of this birdcage frame.
If a person wanted to seal the hole on the outside of this double wall birdcage piece a way to do it without doing what would have to be done from the topside is this. A hole cutter could be used on the inside double wall of the birdcage frame to cut a hole and a patch piece applied thrjough the cut hole to cover the hole in the birdcage frame and stop the water leak. Then the inner birdcage frame cut hole could be closed.

Patrick I have a lot of pictures of all the damaged areas of my 70. I had never done any restoration work like I encountered and took lots of pictures. My pictures are prints from 1986/87. Wish they could of been taken with a digital camera so I could learn to post them like yours.

Another option is to seal around the fiberglass attached fender support to stop the leakage. However the location is pretty much unaccessable.

Jim,

I have a spare birdcage in my shed, so I will go out and look at it to see if I can figure out what you are describing. I assume you don't have a scanner for those pictures. If I can figure out where it is you're trying to direct me I may take a picture.

When I washed the car, I sat in it afterward and had water on the front edge of the seat, the same location that the owner notices it when he has driven the car. As such that seems too far back for the location you are describing - especially since the windshield header is directly above it.

Patrick

[Terry M.]

Re: 72 Windshiled Header repair

The birdcage is like the roof of your house. The water comes out at a different place than it comes in. I have seen pictures of the hole he is referring to, and I know the place it leaks from all too well.

I think the fender will have to come loose from the cowl, or the top six to twelve-inches of the fender has to be peeled back to get to the hole.

[Patrick H.]

Re: 72 Windshiled Header repair

The birdcage is like the roof of your house. The water comes out at a different place than it comes in. I have seen pictures of the hole he is referring to, and I know the place it leaks from all too well.

I think the fender will have to come loose from the cowl, or the top six to twelve-inches of the fender has to be peeled back to get to the hole.

Yes, I understand. We've fought a leak in our roof for years and finally found it.

However, water dripping from the upper windshield suggests to me that anything lower than that isn't the issue on this car. In fact, the owner thought it was the T-top seals but those are in excellent condition and no water came past those on my test.

[John H.]

Re: 72 Windshiled Header repair

This is a midyear cage, but it's the same hole - for spotweld access to the double-thickness weld below it; should have had a plug/seal designed to fill it, but it didn't. This is why the bottom outboard corners of the windshield frame rust out, and then water runs down the pillar and rusts out the sill at the base of the pillar.

[Grant M.]

Re: 72 Windshiled Header repair

There's a Corvette Restoration book out there that I believe was published in (of all places) the UK, and it has an entire section with photos showing repairs to a C3 convertible windshield frame. The access method used (this will likely scare you as it did me when I read/saw it) was to use a saw to cut the rear upper edge of the fender off and then use mat/resin to bond it back on afterwards. The repairs consisted of patches welded in to fill rust holes/missing sections and then ground smooth and painted.

Not for the faint of heart, but it looked like a plausible approach, even to include the fender sawing, and I almost got to the point of tackling it on our (leaky) 78, until my wife decided to sell the car.

Good luck, Patrick!

grant

[Chuck S.]

Re: 72 Windshiled Header repair

This is a midyear cage, but it's the same hole - for spotweld access to the double-thickness weld below it; should have had a plug/seal designed to fill it, but it didn't. This is why the bottom outboard corners of the windshield frame rust out, and then water runs down the pillar and rusts out the sill at the base of the pillar.

John, are you saying it's the hole through which the worker is torquing a fastener ( or is that the spot weld being made?), or the smaller hole at 4 o'clock from the one the torque tool is sticking into?

The hole I thought Jim was describing is round on C3s, and not oblong like the one being used. For some reason, I had always thought the body shop tried to seal those holes with bonding adhesive, but that bonding adhesive didn't stick long.

[Keith L.]

Re: 72 Windshiled Header repair

Sometimes there is no stopping point. Check the top of the windshield on this one and then look at the drivers side lower corner. I only took the firewall off of this parts car to practice for my project car. If I had just looked at the top and sides of the windshield frame I probably would have thought all was well under here.

[Patrick H.]

Re: 72 Windshiled Header repair

That car in general looks far worse than what I'm dealing with. Most of the metal on the inside of this car is pristine.

The owner just doesn't want a wet lap.

Patrick

[Jim T.]

Re: 72 Windshiled Header repair

Patrick I do have a scanner. When I find my package of pictures I will scan a couple and send them to you in a e-mail. Will have to now learn how to attach a picture to a post like the previous poster with his pictures.
His picture does show the hole in the rusted birdcage lower windshield frame, although it is not perfectly round any more.
I was not the builder, however I do not see where this hole was any access to do anything. I just don't understand why it was there. I still have my two new original GM replacement pieces I bought in 1986 of this double walled birdcage piece. I only needed a piece of the new piece to repair my damage. I cut it out and had it welded in. To remove the whole double walled birdcage piece would of been a lot more work and it was not needed.
Seeing the perfect example of the hole underneath where the fiberglass fender support was attached with rivets that Kieth posted reminded me of the glob of bonding ashesive that was in the drain trough of my 70 preventing the enginered design for draining water. The drough was dammed up with the excessive application of bonding adhesive. The drain trough is at the bottom of Kieth's picture of the lower windshield birdcage frame.
Like mentioned in previous posts, the top of my fenders were removed. I consulted a very much experienced Corvette body repairman and while there with my car he took a hacksaw blade and cut the drivers side and told me to do the other side the same way. Have to remove it to fix it.
With only water dripping on the seat I agree that it is not coming from the lower windshield corner. Your repair of the upper windshield area should stop this.
The only leakage I got from the upper windshield was dripping down the rearview mirror and them on the console. It never was much water.