I have an 87 F-150, it had some good sized rust spots on the rear fender wells. I have already used an angle grinder to grind of all of the rust and old bondo. (see pictures). When I ground off all of the old rust and bondo, I found that the rust was worse than I thought- the rust started on the inside of the body because there was dirt packed into the inside of the fenderwell causing the panel to rust from the inside out. I have surface rust on the inside of the panel, I cant get to the inside of the panel to grind off the rust. Is there any way for me to stop this rust
(on inside of panel)? Also, how do I bondo the area now that there is no good metal where I ground off the rust? I can't weld in a panel because I only have access to a stick welder. Do I pack something into the inside of the panel? Any help would be appreicated. (please excuse the poor quality of the pictures)
<img src="http://picserver.student.utwente.nl/getpicture.php?id=277743"border=0>
<img src="http://picserver.student.utwente.nl/getpicture.php?id=277762"border=0>
<img src="http://picserver.student.utwente.nl/getpicture.php?id=277759"border=0>
<img src="http://picserver.student.utwente.nl/getpicture.php?id=277751"border=0>

 

How long do you need the repair to last? I only ask because unfortunately if thats not replaced with metal, it will start rusting again as soon as it gets wet. I'm not trying to be smart or anything. It's just with the way those panels come together, if all the rust isn't removed and then the new metal painted inside with some kind of rust preventive paint ( ZR, Por-15, Rust Bullet, etc) It will be back in a flash. You can fix it cosmetically for now with body filler and paint, but it will be a very short term fix.

https://www.ford-trucks.com/user_gal...oid=15561&.jpg[/img]

https://www.ford-trucks.com/user_gal...oid=15564&.jpg[/img]

Good luck,

 

I have the same problem on my 87 I packed it with bondo and sculpted the fenders. literally. haha Look in jcwhitney or eastwook they make an attachment you can install on the end of your ac arc welder (stick welder) that will make the installations of patch panels easier it only runs around $50 so with a $50 patch panel it might be money well spent. You could get creative with por-15 and fiberglass but it seems your truck looks pretty good otherwise so might be worth a solid repair. Good luck

 

i have the same on my bronco . i have a mig pro 135 welder but never did any sheet metal welding before ,i heard its tricky .any one use one on sheet metal before ..any tips would be a great help ..need to do it soon befor the cancer spreads..lol