I tried using body filler instead of welding on a small rust hole and it came back in 3 months

I had this fender on a 2002 F-150 with a rust spot maybe the size of a quarter. I figured I'd save time and just fill it with some premium body filler instead of cutting and welding a patch panel. Three months later the whole thing bubbled up and cracked worse than before. Now I get why the old timers say you can't cheat rust repair. Has anyone else tried this shortcut and had it fail or did I just use the wrong product?

3 comments

3 Comments

hannahs451mo ago

Did your buddy try sanding it down and using a rust converter underneath first? I had a friend who did the SAME thing on his old Tacoma and it bubbled up in no time because he skipped treating the rust underneath. He learned the hard way that filler just hides the problem until it rots out again.

nora_dixon28d ago

Oh man, that's the thing with converters - I watched my cousin try to rehab an old Ford Ranger and he used that rusty metal primer thinking it was the same thing. Took him three weekends of work and it peeled off in sheets like a bad sunburn six months later. He finally broke down and took it to a body guy who just laughed and told him he had to neutralize the rust chemically before anything else would stick. The whole project turned into this saga where he spent more on do-overs than just paying someone the first time. Now every time I see a truck with that telltale bubbling along the rocker panels I think of his grumpy face holding a grinder.

grant_foster791mo ago

Holding off on rust converter isn't always the worst idea though. Sometimes that stuff leaves a waxy film that paint hates sticking to, so if you grind it clean and hit it with epoxy primer instead, you're actually better off. Your buddy's problem might've been bad prep more than skipping the converter, no?