Paint cracking and stress fractures what should I do?

[BrianPeters1313]

Hey guys, 

I'm starting to work on my Z and I have a question about the current status of my rust/paint. I'm new to working on cars so i'm not yet very knowledgable on all of this stuff. I'm trying to assess if I have a rust problem that needs to be dealt with before it gets worse. The paint on my Z actually looks pretty good, but on some spots there is rust bubbles and what looks like stress cracks in the paint. 

I attached some photos that shows the problem areas. This includes the inside of the hood which appears to have burnt from the previous owner. It's showing signs of rust under the chipping paint. 

Should I strip her down to metal and deal with the rust asap, or could I drive it for another year or so and be okay? Could I simply deal with these spots individually? Thanks for your help in advance.

Brian

[grannyknot]

Brian, It's always a good practice to address rust asap but then a lot of us are dealing with rust that started 40 yrs ago. The hood you could wire brush the loose stuff off and spray it with some rust oil stuff until you can get to it,  but those ridges above the quarter windows are something to be concerned about. That is where the roof was joined to the rest of the body, when I stripped the paint off my early 240Z I found a lead soldering in that seam, now if water has some how gotten under the lead then it is possible that it has oxidized and is bubbling up but it looks to me like there is some movement there, that the body and roof are flexing but not as one, that is not good. If there is movement in those seams then there will eventually be movement in other seams.

If it is just the lead it is fairly easy to dig it out add some filler and repaint, if there is enough movement to break the paint then to properly fix it you have to go down to bare metal inside and out and re weld the seam. It's not like the car is going to fall apart or be unsafe but if it turns out that those seams are flexing too much then it's good to fix before other welds are stressed too.

[gwri8]

+ 1 on what grannyknot said about the seams.  

It looks like yours has a repaint already. A lot of what you will have to do depends on how well that paint job was prepped.

If you are going to repaint it in the future, the sooner you address the rust spots, the better, like that one at the bottom the hatch glass. You want to prevent holes. That will lead you to having primer spots until you have it properly painted. If you don't mind that look then I would start on those spots now and prime them when ready.

For under the hood, I stripped mine to bare metal with Aircraft stripper and used a razor blade scraper. Powerful stuff. Definitely use a mask and rubber gloves. Then, I sanded some and sprayed rattle can primer.  I wound up stripping the whole car that way.  Other folks have done it with media blasting.  Either way, once you start, you're committed. There is no going back. 

Edited December 30, 2016 by gwri8

[wheee!]

Bottom line: do you want a car that is a "driver" for a few years until you decide to purchase something else? Or have you been infected with the Datsun strain of dementia like the rest of us and decided this is the car for you forever? If it's the latter, be prepared for a long road of restoration, repair and refinancing....

[Patcon]

Grannyknot is right there are factory seams there that join the quarter panel to the roof. You need to be careful working on this joint because you can give yourself lead poisoning if you grind on these. I have had cars that cracked here too. I believe they were driven very enthusiastically and that may contribute to the problem. The lead flexes better than thick body filler. So if the during the repaint they filled these full of Bondo that could contribute to the cracking. Being in California your rust won't spread as fast as in other parts of the country. I would definitely treat the rust spots to prevent spreading. I would also be careful of making the car a garage project. IT can be very hard to stay motivated to finish a car once it comes off the road...If you rework the roof seams, remember, body filler isn't waterproof, good primer is, not rattle can stuff...

[jwtaylor]

That joint of the quarter panel to the roof cracks and is a common issue on the early 240's. Forty six years of flexing of this area has taken its toll. I've got the same cracks to repair.  Nissan reinforced that area on the later cars.  I've heard that the metal based fillers may work better in that area as they are able to flex more. I am planning to add Bad dog's rear frame connectors to help stiffen the of the car rear up.  I recall reading that adding a roll bar to the rear will also help stop/control the flexing. 

My car has been repainted at least once and I also have the crazing in the paint.  I used a razor blade to remove the top layer of paint and the crazing goes deeper.  I'm planning to completely strip and go from there.  Way to much filler in places also.

[gundee]

I have been lucky with no cracks on my 72. But I have had a SCCA style bolt in roll bar for 30 plus years.

Same as what MSA sells. I think it has helped reduce the flex alot. A good idea to go along with your repairs I think.

[BrianPeters1313]

Hi all, thanks for all the great info. Since I don't have my own garage right now, I think i'm going to spot treat each problem area and just primer over them. I'll look into the rear frame connectors as well. Would LOVE to start stripping her down but I just don't have the space right now.

 

[palosfv3]

The cracking of the factory lead seam usually isn't the result of flexing but improper cleaning of the flux from the tinning process before the addition of the solder to fill the joint , A common lead application fault that usually ran rampant in a production enviroment .