Cracking around monocoque chassis at jacking point

[ericsinaus]

After having done all this realignment work on the back end wheels and suspension and respraying the side sill panels and ready to put them back on, I noticed a crack running from underneath the side step sill/monocoque channel from just above the square jack tube point up and over to the upper sill near the right angle edge below the aluminium step cover strip.
Has anyone had this happen to their vehicle at this point, is it a common problem on 40yo 911's and how did you repair this crack.
Im sure it's a structural issue being part of the tubular hollow monocoque chassis along each side.

[rowingone]

They make repair pieces for that area that can be welded in place.

[Dpmulvan]

Pics?? Are you sure it’s a crack? You’ll have to strip to bare metal and exam, if it’s not a rust issue you can simply re weld it, I would tig it.

[ErrorMargin]

Yes, let’s see pictures. And what year is the car?

[ericsinaus]

It's a 1980 911 SC Targa.
I can catch my fingernail on the edges. Cracks on both left and right sides in exactly the same place. Would have never seen these if I hadn't have taken the cover sills off to get the rear spring plates off.

How do they repair this. Do they cut out a section and weld a little replacement plate in?? What's the way to go about repairing these cracks.
As you can see I haven't cut the paint back yet but once I know how to go about it Ill attack it.

[jimtweet]

That is the leaded seam where quarter panel joins rocker panel. You’d have to do some digging to see what’s going on

[Dpmulvan]

I wouldn’t worry about it unless you plan to paint it.

[rowingone]

I agree . . if the crack does not extend into the floor area it will not compromise the structure. Old leaded seams can crack like that without impairing the structure beneath . . live with it and if you do a repaint in the future it can be addressed then.

[Showdown]

It’s certainly possible that the flex is just causing the filler and paint to crack.