I put a message about this up on this forum not long ago,i didnt get a very good response,which is understandable concidering the boreing nature of the subject,but i could really do with a bit of constructive information.Im removeing rust at the moment,the bigest bits about the size of the tip of a finger,im getting a lot of different appinions on the subject.My process is to grind the rust away to bare metal,clean the area,rust convert it,clean it again with metho,then bog the area with normal filler in layers,when the hole is filled sand it down and prime it. Should i use metal tech(metal fibro filler ) for the initial hole and then cover with normal filler,what about fish oi. any advice wold be appreciated thanks

Are you meaning that the rust has gone through the panel, or just surface rust?

If the rust has made a hole, then you really should cut the bad sections out and replace them with metal. (Or in some cases, its just easier to replace the whole panel, since you can buy most panels new). Filler should really only be used to fill small imperfections and dents, and even then, using only the minimum amount. if you use it too thickly no only are you not replacing the structure of the car, leaving it weak, but it'll crack and look like crud aswell.

Even if you cant weld, you should be able to cut the panels out, prep it for new bits and get a welder in to weld it up. then finish it off using a small amount of filler.

.. do it once, do it properly. if you dont you'll regret it in the long run

My 2 cents worth

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'78 LS 1275

I agree, if its surface rust sand or grind it off, prime, paint etc etc. but if it is a hole the size of your finger tip on the back of the panel it is a 50c coin size patch of rust. The only way is to cut it out as andy said. Fish oiling is the go behind the panel as well after repair as there will be bare steel and weld.

Good luck!

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Take it easy, & if it's easy take it twice!!