bondo cracks

[mattandhisz]

i have a 1972 240z that i bought in october, and i just got insurance on it and im starting to drive it now. it has had some bad bodywork done before. there is cracked bondo all over. its horrible looking. what does everyone suggest i do about all of this?? thanks.

[MikeW]

The answer to this question depends entirely on how much money you're willing to spend. However, it sounds like much more than a simple repair. You may be able to use some more Bondo putty to fill in the cracks but you'd still need new paint to make it look right. If you're going to go to the trouble of painting then you might as well fix the problem properly. There may be a lot of rust hiding under all that Bondo.

[2ManyZs]

If the bondo is cracked, the only way to repair it properly is to grind it out and start all over again.

If it has been cracked for more than a day, I can guarantee there is moisture soaking into the bondo and if it hasn't rusted already, it will. Bondo will soak up water like a sponge and remain moist for years.

[Mr Camouflage]

Get it sanblasted and repainted, minus the bondo.

Thats what I'm doing to mine. I striped it and found a number of horror stories hiddend under the paint. Layers of bondo, straige onto bare metal, which had just started to develop the beginnings of surface rust. I'm lucky I caught it when i did.

[Zdreamer]

Outta here!

[beandip]

like 2many said if the bondo is cracked or exposed at all it absorbes moisture and will rust the metal under it. Some "body " men to do quick fix will drill holes to pull the metal back out but not braze the holes before using the filler. You can see the noodles sticking out in the back , if they were not knocked off. Moisture will travel in through them , or the exposed material . I had damage in the back of my Z in the vallance below the L plate , because I noticed a small crack in the paint. I looked up under when I pulled the tank and could see the noodles. When I sanded and chipped off the bondo , I found a patch of rusted metal about the size of a football , thankfully it was surface rust and could be pulled out and cleaned off . Altogether there was about 50 holes that we brazed closed. What Zdreamer said he did is right on. Primer is also porus and will allow moisture to penetrate to the metal . So work on one area at a time and keep it out of the weather.

[Zvoiture]

Why does Bondo craze?

steve

[EScanlon]

Did you mean CRACK or CRAZE?

Crazing is where you get a series of small cracks that seem to be in "squares" or "rhomboids". That is, the jagged lines seem to intersect at angles to other jagged lines. Think of shattered safety glass but in jagged straight lines.

Cracking is where there is a complete separation of the material through from side to side (in this case outside to inside).

Crazing is caused by an unsuitable base material that has reacted with the bondo causing it to "wrinkle" and set with poor material in the fissures. The most typical example of this is stripper residue on the sheet metal, although fibreglass resin can cause the same if not properly sealed before applying the bondo or paint.

Cracking is typically due to an impact or sometimes stress due to body flexing.

Hope this helps.

Enrique