1970 T-Top Opening Seal/Crack

[Mark P.]

On the body on a 1970 T-top that my friend owns, I was noticing that it has a bunch of clear silicone caulk placed along the edge where it is cracked along the center divider and the back of the t-top opening. It looks nasty and I thought it needed to be removed and replaced with the original fix, whatever that is.

Was there an original body putty/caulk used like is used today that is painted over when it came off the line originally to fill any void or to smooth out any cracks or separation or is the fiberglass originally smooth, but has just cracked over time? If I'm not describing this very well, I appologize.

Thanks,
Mark

[Dick W.]

Re: 1970 T-Top Opening Seal/Crack

Silicone was not used at the factory. The original caulk/sealer was a product similar to strip caulk, which you can buy at any Auto Paint Jobber

[Mark P.]

Re: 1970 T-Top Opening Seal/Crack

Was it painted over after it was applied or was it left black?

Mark

[Dick W.]

Re: 1970 T-Top Opening Seal/Crack

I was left black. It was used sparingly

[Mark P.]

Re: 1970 T-Top Opening Seal/Crack

Perfect! Thanks for your help.

Mark

[Chuck S.]

Re: 1970 T-Top Opening Seal/Crack

Mark, you need to figure out how to post a picture. What you are describing does not sound right with ANY kind of caulk/sealant.

As Dickie says, a pliable non-hardening sealant like Strip-Calk was used, but IS NOT VISIBLE, and IT IS NOT PAINTED. The sealant is hidden underneath the moldings.

If your friend is using silicone caulk in the center T-top joint and the rear edges of the T-tops to keep water from leaking in on his head, it's probably because the T-top weatherstrips need replacing. The weatherstrips are the primary barrier to water leaking in through the T-tops; the sealant just keeps water from working its way in through the moldings.

[Mark P.]

Re: 1970 T-Top Opening Seal/Crack

I'll get a picture when I get to Portland where he lives this week...it isn't that it's leaking, it's just that it looks bad. The seals that are on the t-tops are intact and again, not leaking. It's the fiberglass where it comes in from that outside finish where it makes the bend downward to the channel where the t-top fits...at that first bottom bend before it hits the opening is where the silicone is placed because some cracking has occurred. Perhaps it leaked in the past...my friend did not put the silicone there, he just wants to get rid of it and needs to know the best solution.

I know...a picture is worth a thousand words. We'll fire one out there on Wednesday for you to look at.

Mark

[Terry M.]

Re: 1970 T-Top Opening Seal/Crack

I don't recall any sealer on the removable roof panels of my 1970, but I am willing to go look.

There is sealer on the stainless steel roof surround. That material is as Dick and Chuck have described, but it is silver or light gray colored -- to blend in with the bright surround. That area leaked early in the life of the car and I added silicone sealant in a misguided effort to stop the deluge. Before I brought the car for judging I removed the silicone because it looked bad and didn't work.

[Chuck S.]

Re: 1970 T-Top Opening Seal/Crack

I just went out and removed one of mine to confirm what I thought...the rear edges and inboard edges of the T-top are more or less a flat surface until there is a step in the fiberglass on the interior side of the T-top.

The weatherstrip installs on that flat thin portion of the T-top just BEFORE the stepdown (up?). If silicone is on the bottom corner of that stepdown, I SUSPECT a previous owner found a leak through a crack in the fiberglass reinforcement (probably from rough handling) and tried to stop it with silicone.

BUT...a T-top should not leak at that location even when the interior fiberglass IS cracked; the top skin is bonded to the bottom reinforcement (the part with the step), and it should be water tight. That says water is getting in through the top skin's bonded joint somewhere...THAT'S the opening that needs to be plugged to stop the leak. The top skin may have some delamination.

For a thorough repair, find the defect(s) in the bond joint, clean it out well with a hacksaw blade, then force catalyzed bonding adhesive into the open joint, clamp it firmly closed, and let it cure. Mask all the painted areas well; you don't want that bonding adhesive getting anywhere but where you want it.

If the joint failure is not obviously on the rear edge or the inboard edges, you'll have to remove the T-top moldings to find it...better come back for more advice if that happens; that eyebrow molding is very fragile and tricky to remove.

[Chuck S.]

PS...

I don't know about all 70 coupes, but my car has the light gray T-top skins, which probably says they are the later Gennite material rather than the dark charcoal or black polyester fiberglass. To be on the safe side, I would NOT use polyester bonding adhesive for this repair...use an epoxy based bonding adhesives used on modern Corvette SMC panels; it'll work with either type material.

[Jim T.]

Re: 1970 T-Top Opening Seal/Crack

The area you referenced Terry on my 70 was replaced by me after I removed all the stainless steel on my coupe to replace the top steel windshield frame and both corners in 1987. I used 3M strip chalk to reseal this area after I put it all back together. 3M strip chalk is paintable so I masked around the chalk and painted it. Has really held up well. I painted it becasue I did not want dirt to get embedded in the chalk. I also used 3M strip chalk to seal the area between the trim and the coupes roof line area. I think the 3M strip chalk works pretty well. With age it is not soft anymore. Don't know why I did not paint the applied 3M chalk along the roof line. You mention a leak. Mine was leaking, it would drip off the rear view mirror. I did not think it was from factory seal stuff since it looked good. When I had my windshield replaced I was standing in the shop watching the man remove the windshield and was quite surprised to see how bad the rust was at the top of the windshield frame. This was where the water was coming in. I drove it home without a new windshield and ordered new parts.