Rocker Panel Rust and Related Issues
 

Well I just got my running boards off and now I can see the full extent of the rust at the pinch weld seam and more generally in the rocker panels. The seam is a little worse than I thought it was, naturally, but still salvageable I think. I want to do a quality repair that will last for many years. So I’m thinking of cutting away most of the rocker panel outer skin starting down low next to the pinch seam and stopping about a half an inch short of the first transition from vertical to horizontal, The horizontal part being what I would call the door sill. As far as I can see, the part that some people call the inner rocker, which I think is really the outer edge of the floor pan, is in excellent shape.I would grind away the outer layer of the pinch seam until only the flange part on the floor pan was left. Then I would clean the remaining structure and paint it with a two part primer, epoxy or urethane. Then I would take some of these aftermarket rocker panel repair panels and cut it so it went from the pinch seam up to the 90 degree transition from vertical to horizontal. Then I would install it, not by welding it, but by bonding it with 3M structural panel adhesive and further fastening it with a large number of stainless steel rivets. Then possibly I would spray the outer surface of the new work with two-part primer followed by a couple layers of lightweight fiberglass mat saturated with resin The fiberglass would serve the dual purpose of protecting the structures from chips which would eventually become starting points for rust. It would also serve to bury the heads of the rivets which would allow me too sand the work out so that it would be undetectable.

I am choosing this approach because I think that Toyota’s design is problematic in the first place. If you look closely at the bottom of the pinch seam, you will see what I believe are weep holes (they are actually more like slots 3/4 of an inch long and roughly an eighth of an inch wide) spaced at different points along the seam, which look to me to be designed to let water escape from the empty interior space between the rocker panel and the floor pan. And I think it has been this way with every preceding generation of Toyota pick up truck and 4runner that I have seen as well. The runner I’m working on right now is definitely rusting from the inside of the rocker panels outward. I have seen bubbles or blisters in the paint that I have pierced and seen water run out of. I think if I were to do a welded repair I would be leaving bare metal inside the rocker area, which would begin to rust immediately. And a spot welded pinch seam is about the worst kind of structure you can possibly have if your goal is to prevent corrosion. Sure, I could squirt Fluid Film inside the rocker panel after I got done welding, but that is surely something better reserved for when you have no other choice and not nearly as likely to result in 100% coverage or offer the durability of Epoxy primer and 3M bonding adhesive.

So there you have it. I look forward to any constructive criticism.I plan to order the rocker panel repair pieces later today and hope to begin work as soon as they arrive. Pictures and copious details to follow as the work progresses.

There's pinch welds all over the vehicle that don't rust out. Use weld-thru primer. Eastwood makes one.

The rockers rust out because the sunroof drains inside there. Plus they get chipped from rocks etc. and the rust starts. The drain holes also get plugged up and don't dry out.

I'd weld it back close to original and paint again after welding and then coat with rust inhibitor and you'll be fine with annual inspections and re-treatment.

The running boards, if still on the truck, cause a lot of damage to the rocker and pinch weld area. In particular right in front of the rear tire arch. They rub through the paint and primer in various spots starting the cancer.

The rocker design is not so bad if previous owners had looked after it. It's a simple matter to include that area in the undercoating routine thereby preventing the corrosion in the first place. There are several access points to get fluid film or the equivalent in the rocker. I put 1/2 a can in each side every winter or 2. Drips every hot day in the summer.

It's a shame we were not all original owners. Could have taken care of them from the beginning. I bet no one expected them to last so long.

Best of luck with the repair.

Where things stand now, at the beginning of the project. The driver side looks much better, but there are blisters in the paint filled with water.

https://wrenchtech.com/images/t4r-ro...0191001-2.jpeg


https://wrenchtech.com/images/t4r-ro...0191001-3.jpeg

Looks fine to me. You can see paint on the inside piece through the hole. I'd cut out that hole and weld in a new piece. The pinch welds don't look rotted. Everywhere there's surface rust but not rot just scrub with rust remover and then coat with Eastwood Rust Encapsulator (no I'm not advertising for Eastwood) or Internal Frame Coating. Then topcoat the visible areas with blue paint match, spray rust inhibitor inside the rockers when it's hardened up and call it done.

Edit: use that hole to clean out loose scale and crap inside the rockers using a pressure washer, any mechanical scraper you can get in there , and compressed air.

If you want to keep this rig, get it on a rust prevention regiment. Looks like its not getting any, and Wisconsin def needs it.

That is Typical.. You want to fix that up before it turns into what mine look like on Tetanus 1. The previous owner thought that foam and paint would patch it up. Get those holes sealed up then get a rust inhibitor coating inside those rockers before they get worse. :-)

For the Rig leaving in the rust belt, it looks really good. :-D
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Hey! You can’t drive without rocker panels. They are a critical structural part of the vehicle.

Just kidding. 3M advises against using bonding adhesive to rebuild rocker panels or any other structural part of the vehicle. I think what they mean though, is that you shouldn’t use it to install new rocker panels on a car with unit body construction, where the rocker structures are a substitute for a separate frame. On a vehicle with a separate frame, the rocker structures are much less critical.

You have a very valid point. Major difference in unibody verses frame vehicle. My passenger is actually cut off.. I went to get the inner rockers and they have been discontinued. I have the outer rockers.. So now I have to make my own inner ones.

I am planning on also welding a 16 gauge square tube in between the inner and outer rockers.

I just didn't want to have to make my inner ones but until I get a used set to template. I don't have a choice. I want to get this buttoned up before winter if at all possible. By next March it has to be done. I will document the rebuild of the rockers section on Brillo Builds.


I figured this ride is the perfect example of what you don't want to happen to your 3rd gen rockers and why its very important to stop the rust when it is very small or better yet not there.

Just like on the POR15 or Fluid Film thread, I put a photo of Tetanus 2 front sway bar bracket hole. As an example of what you don't want it to get to.

I can fix all of this, but its better to not be in these positions if possible. As other forum users have said. Some TLC and rust prevention can really go a long way. :-)

I wish my rockers looked this good. Mine are basically falling off. Didn't really see it when I bought the truck, but after taking off the running boards I realized the extent of the damage. I'm up in Quebec where we have a 50/50 salt to snow ratio though, so I wasn't too surprised.

I am replacing mine as we speak. From what I am seeing. It's best if at all possible to save the inner one. The outer one isn't horrible to replace. However, that inner one with how its built in is a project. Any kind of rust inhibitor in the rockers would be an excellent idea.

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I'd sand them to bare metal and paint with POR-15 then paint over that so it doesnt get exposed to UV Rays. If you're really worried about the inside then I'd drill a hole and spray Eastwood internal frame encapsulator. What you're talking about is effectively worse because you're sealing the rocker in. It's a draining point like others have mentioned by design. My dad just did a bunch of de rusting on his 97 limited and thought it was a good idea to spray expandable foam inside of the rockers................ seriously. Lol told him not too but he did. Toyota designed it this way and its lasted 20 years so why not replicate the design to last for another 20 years?

I am but mine inner were totally gone. You can see I am doing on my build thread. You have 3 ways into a factory rockers w ithout drilling anything. POR 15 works good if you metal left. :] Foam is the worst thing you can do. If they are really bad. It's best to cut the cancer out clean everything out As the rust oxide holds moisture. Then do as wish for rust inhibitors. I am not a fan of Eastwood frame products as I had issues with them. Others have had good success with them. :]

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Toyota 4 Runner Body Panels

I fixed few spots on my 4runner. You need to slowly wire wheel the area and look for spot welds. Then drill out the spot welds and separate the two steels. And basically cut out till you get clean steel. Then it’s all art and patience

@kolelt That link is for 84-89 4Runner's