Crack Between Rear Pillar and Roof

[MDyer]

I've noticed on several Z's that there exists a hairline crack at the point where the rear pillar(?) meets the roof. Mine included.

Is this just a weak point in the structure? Is it evidence of hard driving, where the body flexes?

I'm just going to re-weld; unless that's a bad idea. Attached is pic of mine.

[2ManyZs]

That's the seam where the roof panel meets the rear quarter panel. I can't remember if it's seam welded or spot welded, I think spot welded. It can have a little flex there over the years, as a spot weld is never going to be as strong as a seam weld. Looks like someone has put a little putty there in the past, and probably what little flex has occured, has caused the putty to crack.

I guess the question would be why the filler is there in the first place?:cross-eye

[MDyer]

I've spot sanded all over the car, and the same layers exist everywhere. I think it's some type of heavy primer (?).

[2ManyZs]

Hmm, hard to tell in the pic... I was going by the color of it, it looked to be the same color as the infamous bondo....

Could be some kind of epoxy primer I guess...

[Nigel Mulvey]

Mike,

I posted a similar question about a year ago when I was looking at buying my 240. It too had a crack like yours and I was concerned about spending money on a car that's frame strength was seriously compromised. The response was that the join between the roof and rear quarter occured in this area and that the lead filler used to smooth the join often cracked under the minor flexes of the body. I didn't bother fixing it and a year later it is no worse.

I am currently in the process of stripping back the paint of my 260 and I have found the primer/filler you are talking about in several locations. It is a right PITA to remove. I'm amazed at how much they used, I would have thought a car off the line would have been a lot straighter.

[ZCCOR#109]

As an original owner with a car that has mostly original paint, I will state that mine has this crack on both sides for the past twenty years or so now. I would think that that seam was filled with lead, as that is how manufacturers filled body seams in the past. Now they just leave the seam as a design.

Obviously this is a structure issue with the Z. I have no knowledge of how the joint is welded, but this crack in the paint comes from flex.

If I were repairing, I would want to go down to bare metal and weld.

I'm not sure a strut bar would help, it may put more strain at this area, or may not?. A roll bar, 4 point, would do the job of limiting flex.

[2ManyZs]

Now that it's been said, I'm pretty certain they are spot welded only, and then the lead filler is used to fill up the seam. I don't see why you couldn't grind it down and seam weld it and get rid of the lead if you so choose.

As far as getting rid of all the flex, with strut bars and such, it would be almost impossible as a unibody is designed to have a bit of flex as it is inherent in the design. You'll never get a unibody to have the rigidity of a body on frame, unless you spend a lot of money.....

[dozer171]

my 78Z did the same thing. if you look at the GM f bodies of the 80's and early 90's, a simmilar thing happens to them in the same spot. that is where the flexing causes a break in the seam.

DO NOT WELD THERE!!! they are joined with lead body solder, which is probably why they broke to begin with.. i simply used a soldering iron and reworked the led in the area. if you weld it, you're going to make a BIG mess... also, be careful sanding as the lead is very soft and will start scratching real bad if you start sanding. do just enough to smooth it out after you reflow the lead.

[Zedrally]

Originally posted by dozer171

i simply used a soldering iron and reworked the led in the area. if you weld it, you're going to make a BIG mess... also, be careful sanding as the lead is very soft and will start scratching real bad if you start sanding. do just enough to smooth it out after you reflow the lead.

Brilliant,

I had been wondering if I needed to take an oxy torch to this. I believe that the lead solder you are refering to is actually called wiping metal. This has a much lower melting point than lead solder and is generally used on high quality resto's.

[Brett240]

when these cars are resprayed alot of painters use body filler instead of lead jointing but either way it will crack. i had mine lead jointed and put a strut brace on and the thing still cracked in a month. i dont think it will be a structural problem at all as mine too havent gotten any bigger in a yeay and a half

[mbentsen]

Hi Mike,

Sorry to scare you, but you may want to check metal behind your crack.

If you check out my gallery photos you'll see what I mean.

Both sides of my 240z 73' looked not to bad from the outside, until I began to investigate the undelying layers of metal.

It seems like the metal wasn't treated properly from Datsun.

You might be able to poke a little dentist mirror and flashlight through gaps from the inside, to get a view, without cutting it open.

I hope you don't have the rust that I had.

Rgds,

Michael

[MDyer]

I don't think it's in bad shape. Given the hairline nature of it, I think if rust exists, it would be readily visible. I'll take a look.

Don't take this the wrong way, but after looking at your gallery, I'm sure that I'm starting with a car that APPEARS to be in much better structural shape....

That said, it's still worth a look!