When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
'twas raining the other day and, of course, ze T-top was leaking. I plan to replace all the weather stripping quite soon.
However, I noticed on the passenger side, it was leaking from under the dash... This view is with my head at the bottom of the footwell facing the seat. The four bolts sticking out are from the wiper transmission mount.
YES....100% positive that it is your firewall panel that is pop riveted to your 'birdcage'.
This is a very common problem due to the type of sealant that GM used and over time..it can become brittle and fail.
I have lost count on the number of Corvettes that I repair this area to get leak to stop.
And ..for what this is worth:
I have written this many times and this area that you are now having a problem in getting a leak. Can easily be attributed to improper supporting of the car when jack stand are used.
If jack stands are placed in the front support area that GM specified...all of the weight of the front end is now applying pressure to ALL of the fiberglas components that are attached to the firewall and plenum. And knowing that the firewall and plenum are basically attached wit pop rivets and bolts/screws. It only stands to reason that these fasteners can be stressed and cause for the slightest bit of movement the first time the car is supported in GM's manner. Then the next time it is raised and supported...it adds to that. Then after the 100th time....people ask why the gap between top hood surround and door are now messed up.
DO I have 100% empirical proof that this thought has validity. No I do not. But I do have common sense and have seen enough Corvettes in my time where I can clearly see movement when the car is improperly supported. AND on those cars that had wide gaps at the top hood surround and door...when I removed the front clip and the gusset that is pop riveted to the birdcage are. The three rivets have seen better days and were really not helping out..and the sealant that GM used broke away..an moved under the gusset and thus acted like a shim causing the top hood surround to be raised higher.
Those that choose to follow GM recommendations can do so. I myself choose to do it in a manner that will not cause for problem in any of my customers Corvettes. When the car was new or few years old is one thing....but when it is 40+years old...should that not be taken into consideration??.
And if a person wants to follow what GM specifies. I hope that it always works out well for you.
DUB, how precisely would you lift and support the car. Where would you put the floor jack and where exactly would you put the jack stands ?
Question 2: how does one fix this... I take it I have to dissassemble, re-rivet and seal? It might take a few months till I get to that; so many other things to sort out. Anything else that I can do beyond not driving in the rain ?
Those that choose to follow GM recommendations can do so. I myself choose to do it in a manner that will not cause for problem in any of my customers Corvettes.
I had this issue when I bought my Vette. I removed the wipers and cleaned all the old undercoating from the wiper bay. I used a HF heat gun and that stuff came up like peanut butter.
There is a body seam there that opens over time.
After all was removed I sealed that seam with silicone. After that I put a light coat of undercoating on top. I then cleaned and reinstalled the wipers.
Lots of work but my leak problems are gone.
I even had rust on the speedo/tack cans from this same leak.
I know I have to reseal this area may times...and it comes down to this.
Depending on how badly rusted the exposed flange of the birdcage is...that really can not be see in full entirety. I will mix up black epoxy primer and inject it into this area with a syringe and have towels in the car to catch what drips. On seem cars...I pull dash panels and such so I can see it better and put towels in a better location to catch the drippings.
The next day. I go in with the CRLaurenece CRL-1716...which is s pump grade...flow grade sealant that skins over.
I pump it in and let it flow and eventually it will seal and I can get the top visual surface looking good.
I have also used the 3M black strip caulk and forced it into this area . But that is up to whoever is doing it. On some cars the owners do not care and are looking for an immediate fix that darn near costs them nothing....and the warranty on that work is basically what they paid for the work performed.
The 'Flex seal' sounds like a good product. I have never used it and have not gotten around to getting any of their products and see how well they actually hold up.
IF the panel is still riveted to the birdcage...I would seal it up and move on. IF the rivets are snapping off due to whatever reason...then that person will need to decide what the next step would be. Because thinking that using a structural adhesive to bond this area actually would not work for any length of time due to there is no way to properly prep the surfaces that you expect the adhesive to bond to.
I do everything I can by using the rotors as my point where I put my jack stand...That way the car is being supported by the suspension and NOT the frame.
When I am working on the front suspension...for example...and the suspension has been removed. I use my taller jack stands and when all the parts are out. I go up in the hole where the coil spring goes and put the jack stand there.
When I am ready to work on it and get it re-assembled. I support eh car by the bottom of the engine cradle and have jack stands slid back so they contact the frame in an area where I know they would hold up the front end IF the car moved and slid off the floor jack. BUT..I am not lowering the car on these jack stand back by where the idler arm area is. And I am NOT allowing any grass to grow under my feet. I get in and get the job done....then I support it and let the floor jack down. And I have a really good sturdy floor jack...not some cheezy piece of &^%$. 30+ years of doing it...never a problem at all.
On the rear suspension..if it is all out and being worked on...I use my taller jack stands and get them to support the car by the differential crossmember area. It all depends on if the exhaust is still in place or it has all been taken out.
This is how I use the jack stand...and I NEVER EVER have had a car fall off of them....nor has this method causes me to damage ONE THING on the car.
My whole way of thinking is that when I get it up and supported....when the end of the day comes or I am stopping on the job...I want a method to support the car that is bring the contact points of the jack stand to either at the point where the car actually makes contact with the ground (which is why I use the rotors)...or further out in an area of the frame that can aid in supporting the weight.
Because on convertibles...if the jack stand is placed right at #3 body mount area....look at all the weight of the car that is hanging out past it...putting all that stress on your rear clip and eventually...you will watch your door gap a the top of your door widen like crazy due to this fatigue. And knowing that coupes are stronger in the rear area due to the added upepr frame.. I STILL put the jack stands where I know I want them REGARDLESS if it is a coupe.
And YES...a person can place the front jack stands UNDER the lower control arm where the shock absorber is located.
Hopefully this makes sense....if not... I guess I am just
The rivets seem intact. I really appreciate all the feedback on how to handle this; I look forward to getting this job done. It is a matter of pride for me to make sure my ride as no leaks whatsoever.
I do have one follow up question for you, DUB. In my old car, I would lift the front up putting my floor jack under the engine cradle/cross member. I am reading that, on a 1969 Corvette, this can damage the cradle and lead to alignment issues. And indeed, there seem to be some dents in the cradle/cross member.
YES...I lift up from the center bottom of the cradle..BUT...I also protect this area on those cars where the bottom of the cradle has not already been crushed by someone lifting it without trying to protect it from crushing inwards.
On some cars I use two floor jacks and lift from each side slowly because I drove the car up into my ramps that lift the car up about 4 inches. And I put the floor jacks under the control arm area with my padding ( if needed).
And on the cars with super suspension from VB&P where the transverse spring is in the way...I lift it up in another manner.
Keep in my floor jacks have large saddles with good catch fingers on them.
I have also fabricate up a plate that fits the contour of the boom of the cradle with padding on it...but it rarely gets used due to the padding I use works great..has great grip and so far...has not damaged any of the restorations have done that come in for service and effected the powdercoating/paint on the bottom of the cradle in any way.
Where does this under dash leak come from
