Floor Pan

Where Jeeps rust and what fixes it

Jeep bodies rot from the inside out at predictable spots. On a CJ or TJ the floor pans go first where carpet or mats trap water, followed by the rear corners and the area under the roll bar feet. On a Cherokee XJ, Grand Cherokee ZJ and WJ and Liberty KJ, the rocker panels, the doglegs ahead of the rear wheels and the rear wheel arches collect mud behind the plastic cladding and rust through while the paint on top still looks fine. The panels in this category are stamped to the factory shape so the repair can be welded in and finished rather than patched with flat sheet.

Types of panel

• Floor pans: front and rear sections for CJ5, CJ7, Scrambler and TJ, some including the under-floor support rib or brace that is usually gone too.
• Rear center panels: the body section below the tailgate on early Willys CJ-2A and CJ-3A models.
• Rocker panels: the full length lower sill under the doors, sold by side for the WJ and KJ.
• Doglegs and wheel arches: the curved panel ahead of the rear wheel and the arch itself, sold by side for the ZJ and WJ, sometimes combined as an upper arch with dogleg.
• Tail light body panels: the rear corner that carries the tail light on the TJ and LJ.

Ordering the right piece

Panels are sold by side, driver or passenger, and by position, so confirm both. Model years matter: a 1976 to 1983 CJ5 rear pan differs from the CJ7 version, and the ZJ and WJ Grand Cherokee arches are not interchangeable. If the old panel is too far gone to compare, measure the opening you will cut and check it against the panel dimensions. Buy a little more panel than you think you need; cutting a large panel down to fit is easy, while stretching a small one is not. Order the support ribs and braces at the same time if the kit does not include them.

Cutting out the rust

Strip the interior, disconnect the battery and remove or shield fuel lines, brake lines and wiring under the floor before cutting. Mark the cut so it falls on reasonably solid metal, at least an inch past visible rust, and remember that rust under the surface is usually wider than it looks. A cutoff wheel or air saw works for floors; a spot weld cutter frees factory seams on rockers and arches. Keep the old piece until the new one is fitted so you can transfer seat bolt locations and brace positions.

Fitting and welding

EDP primer is a thin electro-deposited coating that keeps the panel from rusting in storage. Grind it off wherever you will weld, and leave it elsewhere. Test fit with clamps and self-tapping screws, trimming until the gaps are even, then plug weld or stitch weld with a MIG in short bursts to limit heat and warping, moving around the panel rather than running a continuous bead. Butt welds on floors are fine; lap joints need seam sealer on both sides so moisture cannot sit between the layers. Grind the welds, treat the bare metal with epoxy primer, seam seal every joint, and paint. Undercoat the bottom and replace any drain plugs so water has a way out.

Preventing the next rust-through

Rubber floor mats trap water and are a major reason floors rot; a rubber liner with raised edges that you can pull and dry is better. Clean the inside of rockers and the area behind the rear flares every spring, and keep the factory drain holes open. A floor that is welded in and sealed correctly will outlast the original.