How To: Repair 2007-21 Toyota Tundra Bed Floor Rust + Prevention
If you own (or are thinking of owning) a 2007-2021 Toyota Tundra, there’s a major issue that you need to keep an eye out for – bed floor rust. This post will go over what I found on my 2007 Tundra, how I proceeded with the bed floor rust repair, and how to potentially prevent it in the future!
This bed floor rust repair required the help of a friend to lift the bed off of the truck, a welder, and lots of labor hours. It’s not a simple job for the new DIY’er, BUT with the right connections and help, it’s by far the most cost effective solution. All in, I ended up at less than $800 for the full repair including bed liner, undercoating, and fender liners. For comparison, I couldn’t find a local body shop that was willing to repair the rust (so not an option at all), and a clean rust free used bed was a minimum of $1500 + 20hrs round trip drive + paying a body shop to color match it AND not even having any better rust prevention measures in place.
This is a long post, so settle in. Read on to learn more.
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The Damage
This truck is a 2007 Tundra that spent it’s life in south-western Ohio and nearby bordering Indiana for all of it’s life. Not the saltiest states but also by no means a “clean southern truck”. It was treated with Zeibart products on the frame, underside of body, and rhino-lined inside the bed when brand new. However, despite this seemingly great prevention, some critical design flaws still allowed the rust to creep in. This may have been covered by Toyota’s corrosion warranty at one point, but with a truck this age it’s far out of coverage.
Here you can see what one of the bubbles in the rubberized bed coating looked like before it was opened up. Then after I peeled it back with a paint scraper. Wow! That was a lot worse than it looked! The damage is focused in four main areas that have a significance I’ll show you later. Literally a “rust bucket”.
The Cause(s)
The main problem (in my opinion) is that the seam sealer applied from the factory is not applied in a controlled enough fashion. The variation in application from bed to bed can be shifted multiple inches in the x-y axis! Next, the seam sealer doesn’t cover all exposed openings between layers of sheet metal. This allows a path for water/salt/debris ingress. Which then gets trapped inside by the other seam sealer that is there. There are 4 key areas under any 2007-2021 Tundra bed that have these flaws, no matter if it’s a 5.5, 6.5, or 8.1 foot long bed.
Below you can see the issues in greater detail. On the left, we have a marked up picture of the THREE layers of metal in the trouble areas. 1, is the bed floor, 2 (outlined in red) is the rectangular support plate that sits between the bed floor and item, 3 (outlined in teal) is the stamped cross member. These three items are spot welded together and seam sealed….sort of. They have unknown coatings between.
In the picture on the right you can see red arrows pointing to where the black seam sealer isn’t fully applied to all of the gaps and the edges. Especially around the wheel well where road spray is constant – this is a recipe for disaster. This is also why the rust is only focused in these four distinct areas where those 3 parts are sandwiched together. Google search 2nd gen tundra bed floor rust and the trend in location will make a lot of sense. Most people will blame plastic bed liner inserts or lack of cleaning under the truck but even with my clean and coated non-plastic liner-ed truck the issue occurred.
Bed Floor Rust Repair
First things first. If you’re planning on welding on a truck bed, it’s best to just remove it from the frame. This will allow us to do all the welding away from the fuel tank, have access to both sides easily, and take our time to do it right. In addition to those benefits, it allows us to check in on, and clean up the frame while it’s easily accessible.
Remove the Bed
I was lucky enough to have a friend with a steel building with a strong frame to strapped a chain fall up to. Some other options are to strap to multiple ceiling trusses or joists, beams, strong tree branch, use a tractor, build a gantry, etc. Get creative. The bed is only a few hundred pounds but it’s awkward for 2 people to manage.
Even though the bed floor was rusty, with lots of PB blaster and an electric impact gun, I was able to use a t-50 torx bit to pull out all 8 bed bolts without cutting or breaking any! The next step is to detach some of the wiring clips and unplug the tail-lights. Trailer plug wiring harness can be left connected. Fuel filler neck can be easily removed with four 10mm head bolts then wiggle the surround out of the hole. Put the fuel cap back on to prevent junk from getting into the filler neck.
We then attached 4 ratchet straps to the 4 OEM tie down points of the bed and lifted it with ease. Keep an eye on the mudflaps and fuel filler neck while slowly lifting. Some moving blankets draped over the front corners of the bed protect the cab from any minor rubbing or bumps. We carefully tipped the bed up, and it sits quite stable on the bulkhead end, ready for bed floor rust repair.
Cut and Weld – Bed Floor Rust Repair
Next, the hardest part of the whole job. I was able to source a bed fairly locally from a 2015 tundra 6.5′ that was rolled in Tennessee and was being parted out in Kentucky. While the bed looked absolutely useless to anyone else, the floor was very clean so we decided to graft over the entire crossmember+bed floor sections, front and rear. This would limit us to only needing to drill out a few spot welds on the fender wells. This would also ensure structural integrity of the cross members. We only needed to carefully measure square and diagonals between bed bolt holes to ensure proper alignment.
Panels were then carefully marked and cut using an angle grinder and cut off wheels. Edges of panels were prepped with 2″ roloc disks on a right angle pneumatic grinder. The old bed liner (both types) were best removed with a knotted wire cup brush on the same angle grinder. The panels were when painstakingly tacked and welded in with my friends Lincoln MIG welder. Any spot weld was coated in a zinc weld-thru primer first. There were a couple extra man made holes (oops) that were repaired while we were in there. Great opportunity!
Finish Work
After the new panels were welded in and welds cleaned up, the top side was covered with self etching primer. The bottom side got coated in chassis saver paint (still left over from the 4Funner project). Then we unloaded an entire tube of seam sealer on the welds, missed spots from the factory, and reinforced any factory sealer that we could. While I had the seam sealer out, I decided to steal the TUNDRA bed logo off of the 2015 bed and apply it to my 2007 bed. A little easter egg for this project!
This picture shows the space that can naturally occur in manufacturing between the spot welded parts 1 and 2 in the diagram at the top of this post. I opted to drill a small access hole in the bed floor at each location to treat the gaps. I filled them with a phosphoric acid rust converter (which comes in handy for many other projects too), followed by air to blow it throughout the cavity, and let that dry 24 hrs. The next day I followed up with Wool Wax Creep N’ Crawl cavity wax formula to fill the void. After carefully cleaning the holes they were sealed over with seam sealer, as well as lots of extra seam sealer applied to the underside of the bed. This should help prevent any future rust between the problem parts.
Bed Liner
For this project, I opted to go with the Raptor Liner brand of spray on bed liner. It has great reviews for being easy to use, durability, and was advertised as being able to coat over the existing mix of bed liners that I had after the repair with proper prep. I ended purchasing two kits and only using 6qts total to get the desired coverage and finish in 3 coats.
Prep
To prep the bed, first wash and degrease. I used a POR15 degreaser/cleaner that I had left from the 4Runner frame coating project years ago and my electric pressure washer. Then scuff up anywhere you want bed liner to stick with an abrasive nylon cup brush on a rotary polisher. Warning – do NOT be temped to run this brush on an angle grinder. It will self destruct if spun at 10,000 rpm, hence speed 2-3 on this cheap polisher. Then pressure wash the bed out again and allow to dry thoroughly. Recoat any bare metal with self etching primer.
Tape off all the edges with painters tape and cover the entire truck in paper or plastic masking to prevent overspray. I opted to bed line underneath the plastic bed rail caps because they rattle and wear into the paint over time. Complete the final wipe down of the entire inside of the bed with 50% diluted Isopropyl alcohol (I get 91% from local CVS and water it down to ~50%). Finally, if you really want to go overboard like me, spray on some UPOL adhesion promotor per the instructions on the can. Pay special attention to the tight corners and difficult to scuff up areas.
Safety First
Don’t forget your PPE! Tyvek suit, safety glasses, nitrile gloves (these are my favorite for all shop projects and BBQ too!), respirator, and some shoes you don’t care about. I used the spray gun provide in the kit. My air compressor had no problem keeping up, especially at these low spray pressures.
Spray
Now you’re ready to mix the bed liner per the instructions and spray! Allowing the coating to flash off between layers, I started at 60psi for the first coat to go on smooth. The bed rails only got one coat. The second coat went on at 50psi for slightly more texture. The third coat went on at 40psi for as rough of a texture as I could get. This was done for traction as well as higher build to attempt to hide all of the imperfections from not feathering the old bed liner out well enough.
As you can see, it didn’t hide all the work that was done on the bed floor. But it looks dang good! Cured for heavy use in 7 days. So far it seems tough as nails. I would easily recommend the Raptor Liner product, and use it again. I would even paint a whole vehicle with it in the future! It laid down so much easier than HVLP paint. Very happy with it.
Future Rust Prevention
There’s two major recommendations I’ll make for rust prevention to avoid future bed floor rust repairs. If your bed is still fairly clean (looking from underneath) and fairly new, you might be able to save it now!
Undercoating
Undercoat your truck with a product of your choice. I’ve tried fluid film, but it was too watery, washed off quickly, and has a lingering unpleasant odor. The improved version from Kellsport is Wool Wax. It’s thick, sprays on nicely, creeps and clings well, with a less offensive smell. They offer full kits with spray guns, wands, plug kits, and various versions of the product. I like the straw color original Wool Wax, and also used the Creep N’ Crawl version in this bed floor rust repair as mentioned above. I spent some time painting the bed side supports and anything else I could reach with chassis saver paint for good measure.
Fender Liners
The final recommendation for bed floor rust prevention on your Tundra is improved rear fender liners. When asked why aftermarket companies don’t make any rear fender liners for our trucks, they say “because they already come with them from the factory”. Too bad the factory liners don’t cover the key areas discussed at the beginning of this post! Luckily, the smart members on the Tundra forums have come up with a great solution.
Enter – the DIY custom rear fender liner. Okay I’ll admit that I like it because it’s a DIY project. It’s a bit tedious but you simply cut out a liner from this roll of plastic. Then, bolt it in place to factory locations using some u-nut clips. The objective of these liners is obvious: prevent road spray from entering the poorly seam sealed and vulnerable areas of the bed. Even though we think we’ve sealed them up, we don’t want to do this job again. Great insurance, or a mod for someone who’s bed isn’t rusty yet. You can save it now!
