Hi Guys,

I have had my 2002 F-150 for about four months now. There were a few bubbles in the typical areas on the lower sides of the bed. Behind the rear wheel had broken through the paint, but not through the metal. My dad and I sanded the areas down to bare metal, treated it with rust killer, primed it and painted it. A week later, the rust started to weep through the paint again. It was a lot of work to fix it, and wanted to be sure that I do it right when I do it again. Also, there seems to be some factory undercoating stuff along the bottoms of the rockers. There are bubbles under it, but when I try and sand it off, it melts. Is there an easier was to get it off? And what exactly is it? Thanks guys.

 

Try wiping the undercoating with gasoline. Should take it off.

 

If it is painted over then it is probably the chip guard that is applied to the rockers. You should be able to find some sprayable chip guard at a auto paint supply store. Not sure if they sell anything like that at an auto parts store.

 

I have the same problem with the paint over the rear wheel wells. Fixed it and a week later it was back. I noticed the paint bubbles are filled with water, but the metal is solid and has no holes in it.

Anyone else have this problem and how did you fix it.

 

The undercoating is a rocker guard. Use a heat gun and a metal scraper. It'll peel like a banana if you get it to the right temperature. Not too hot though, or it just makes a mess. Other than that, 40 grit on a orbital sander will help alot too, followed by 80 grit. The heat gun works best, and it is way cheaper than sandpaper.

When you said you treated it with rust killer.... what exactly do you mean? What did you use? did you sand it after you were done? It's kind of a catch 22 with most of those products. For them to work as advertised you cannot sand them, because you break their protective barrier. But you cannot paint them without sanding. Dammed if you do, and dammed if you don't. Honestly though, all of those products are a temporary fix. Rust wins, every time. The best these products can do is slow the process. You want no rust, cut out the cancer, and weld in new steel. Period.

What primer did you use? There are so many different products out there, many need an etch primer before the actual filler primer is applied. You generally get what you paid for too. Look for a "self etch" primer if you only want to buy one product.