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Rocker Panel Rust Repair

Paul Fithian

Elite Explorer
October 12, 2016
Reaction score
City, State
Long Beach, IN
Year, Model & Trim Level
2007 Job 1 RWD V8 Limited
I removed the rocker panel cladding to paint them and inspect the rocker panels for any rust.

I found some significant rust in the right side and some on the left side also. I cut out the corroded sections to begin the repair. See below.

I wire brushed all the loose rust off and treated with Ospho, applied with a spray bottle to treat as much of the interior sections as possible. I will coat these areas inside and out with Chassis Saver after it has a chance to thoroughly dry out, then patch the holes with 1708 oz biax cloth/epoxy and body putty.

Any other suggestions?

Right Side as Found.jpg

Right Side Ground Out.jpg

Left Side Ground Out.jpg

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I wish you luck with rust in the body seams etc, but try Rust Dissolver to treat any visible corrosion, and all seams. That product is water thin and will wick into seams, where you cannot reach. Sealing rust in where it already exists doesn't stop it from spreading, I'm betting you know that already. The best you can do is treat what you can see and reach, and seal it up well with corrosion treatments, plus undercoat to finish with. All of those cavities which aren't sealed due to holes for trim etc, and rust through, those will be full of rust growth. Those are what I'd most want to do something with, using the Rust Dissolver, and other converters after the initial treatment. Regards,

I had to cut out a bit more on the right side to get into non-rusted steel.

All areas have been treated with Ospho. I will let this dry out for a week or so and apply Chassis Saver to all interior and exterior areas behind the rocker cladding.



I found a lot more rust inside the rocker panels than what I had assumed. On the right side, I removed the entire rocker panel below the cladding fastener holes. I want to keep the holes intact, as the spacing is critical for reinstallation of the cladding.

I ran a piece of 3/4" masking along the top edge of the holes, then cut along a line at the bottom edge of the tape. I ran the cutting wheel along the bottom edge of outer rocker panel to remove it.

There is an intermediate stamped section between the inner and outer rocker panels that is spot welded to the door sill and the outer rocker panel. Most of this was rusted through and made up the bulk of the rusted pieces.

I will grind down what's left, treat with with Ospho where possible, and prime/paint what I can reach in the inside with spray paint and/or Chassis Saver. I will form a new rocker panel from the cladding holes to the bottom flange with 1708 biax/epoxy/body putty then prime and paint. Should prevent further rust out and extend the useful life of the body by quite a bit.

This truck spent most of its life around Cincinnati, which doesn't get a lot of snow or salt on the roads. I'm sure one of these from further north would be a lot worse.

Rocker Panel Cutout Tools.jpg
Rocker Panel Right Side Inside View.jpg
Rocker Panel Right Side Removed Items.jpg

Rocker Panel Right Side Cut.jpg

I'm so scared to ever look behind that cladding....

OK, so this is still a work in progress. I thought I would share what I have found and why these Explorer Sport Trac rocker panels rust. A sketch and picture helps with the explanation, see attached.

Water/salt enter the upper cladding clip holes in the outer rocker panel. This drains down to where the outer and middle rocker panels meet, which are spot welded together at the bottom. Trapped salt water starts rusting at the spot weld, and destroys the middle and outer rocker panel, from the inside out. There is no way to prevent this, as the upper cladding clip holes are not sealed and allow for water intrusion.

The only way to repair this is to cut out both the outer and middle rocker panels, the weld or fiberglass new material in. Otherwise, it will just rust out again.

I was amazed at how much area of the middle rocker panel was destroyed by rust. At least half of it, starting with the section behind the rear door and forward up to the back of the front door. It was basically all gone from about an inch above the spot welds along the bottom.

Rocker Panel Cross Section.jpg

Rocker Panel - Reason for Rust Formation.jpg

That's a good analysis of what's going on. I think it would be wise to use a rust proofing and spray it through those holes in the body, along the side as well as the rear quarter or hatch. I hate seeing any trim which is held on by clips, through holes behind them.

Thanks for the motivation, I have a lot of holes to think about treating in some way.


But I would bet that these start to rust within a few days of the first drive in the rain, whether there is salt or not.

The design traps moisture into the spot welded area, with no way to retain paint protection after welding.

Yeah, the bottom of those panels is pinched together, with tiny gaps from what I recall, to let water drain out. But any kind of holes or access points are bound to get moisture into them, and also to plug up if they are meant to drain.

It doesn't rust at the bottom vertical pinched/spot welded seam that has drain holes. These were in pretty good shape on both sides of mine.

It rusts at the bottom spot welds between the outer and middle rocker panels. There is no good way to get to these areas for treatment. But if there was, it would have to be done before the truck was ever driven in the rain.

The fix I am using with 1708 biax and epoxy should be a permanent solution for this problem. Stay tuned.

Did your trim pieces, the clips, have little round foam doughnuts behind them? I recall those for my running boards had those, and I forgot if I had any missing or damaged.

No. The clips did not have seals on them.

From what I can tell, the driver side cladding had been removed to replace the left front fender.

The passenger side looked like it had never been removed from the truck. There was no difference in the clips.

The replacement clips I obtained ( did not have seals either.

But I think those seals would be a moot point. Some water would still get in and start to rust the rocker panels.

Thanks for the link/source, those are the right large clips. I'm sure some of mine had "seals" on them, and it would be a good idea to reduce any flow through the holes. I might try some Ultra Black and see how hard that is to install the clips with it. My truck has the holes in the fenders for the big flares also, but my big concern will be the lower body panels that see that road salt the most.

I was able to sandblast all of the inside area of the rocker panel from the cut out areas, and coated as much as possible with epoxy resin.

The 1708 biax tape ( I used formed an excellent rocker panel shape and will be filled after hardening with an epoxy/microballoon mixture to fair it out.

In the first picture, you can see two of the strong disc magnets ( that help to hold the biax in place along the inside edge.

Work in progress, more to come.

Biax Tools.jpg

Biax Rough 1.jpg

Biax Rough 2.jpg

Looking good.

I like that, good progress.

Finally completed this repair. I wanted to leave it with the raw fiberglass over the winter to see if there was any delamination. All good, no sign of separation or water retention.

Some pictures showing the completed work. New clips on the cladding to secure it to the body holes.

Rocker Panel Repair Drill Biax.jpg

Rocker Panel Repair Primed.jpg

Rocker Panel Repair Painted.jpg

Rocker Panel Complete with Cladding.jpg

That looks great, excellent work. Those rocker areas are almost impossible to not develop any rust. The holes along the sides allow water in, and the weep slots along the bottom have to be there for draining, but time and debris plug them up. That trapped water above will eventually eat any rocker, whether up North or not. I need to get to mine and save/treat them soon. Everyone should get under theirs and take a look, and get to sealing up the seams, and breaks in the paint etc.

Why not just delete the middle rocker, or cut the bottom section of it out completely so you still have structure in the top lengthwise?

Before anyone talks about structure I need to mention that the Bronco II had completely open rocker panels on the inside.

Sorry about this photo, I haven't found any others to illustrate my point better, but you can see in the middle right hand side of this photo the open panel. I figure that if 100% of the salt water can run off, then the panel would never rust like they do on our Sport Tracs.


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Finally completed this repair. I wanted to leave it with the raw fiberglass over the winter to see if there was any delamination. All good, no sign of separation or water retention.

Some pictures showing the completed work. New clips on the cladding to secure it to the body holes.

View attachment 163238

View attachment 163239

View attachment 163240

View attachment 163241

Dam that came out sooo good. I wish you were in the Jersey area Id pay you in a heartbeat to do that to my 2DR Sport.

I'm in desperate need of official rocker panel replacements for the 02-05 Explorer Sport Trac 4DR. I say Sport Trac because it is impossible to find them for the 01 to 03 2DR Sport. If anybody has a part number for official rocker panel replacements for the 01-03 2DR Sport or the 02-05 sport trac or if you can even find some decent ones in a junkyard I'd pay good money and be forever in your debt.