I have a 2007 Ford F150 that is just starting to show paint blisters above the rear wheel-wells. From what I’ve read, I’ve found that Ford put some kind of foam between the walls of the fender above the wheel-well to deaden sound. This foam holds dirt and moisture causing premature rusting through above the wheel well. Rust-through in this area is a common problem with a lot of pickups.
So far, the blisters have not broken through, and I’d like to figure out the best way to stop further rust if possible. Fixing the outside shouldn’t be too big a deal, but I’m not sure what to do to stop the rust between the fender walls. I’ve heard that I can remove the rear tail-light and stick a wand in there and just soak it with oil. I’ve read other places that Fluid Film is a good choice for this. Here, on Eastwood’s site I found the internal frame coating, but I’m not sure how well that will work over existing rust and dirt/gunk when I can’t get to it to clean out. I also don’t know that the supplied hose (with the Eastwood Internal Frame Coating) is long enough to do the whole fender. There is an box-channel just above the wheel-well (arched, follows shape of well) – I could get into that with the Internal Frame Coating, but I’m not sure if that channel is open all the way around, or if that foam is up in the top (can’t see in that far).