Water sealing the third gen bed

I got me an Alu-Cab canopy recently, and surprisingly, the canopy had way fewer leaks than the truck bed itself. When I'm driving through rain, the bed leaked copious amounts of water through the gaps in the front of the bed right behind the cab. Here is an example:



There are a number of videos on YouTube describing the same leakage, and most people seem to fix it with silicone caulk (e.g. https://www.youtube.com/watch?v=nlTcsIxWwk0). I chose to use "Flex Tape" because it might be easier to remove and clean up, and it has mostly but not entirely eliminated this source of leak. A little bit of caulking or more flex-taping should fix this.

What I'm surprised by is a leak in the aft of the bed, near the tailgate, as well as from around the 110V power outlet bay:


In the latter image, the water seems to be leaking from under the plastic cap on the side railing of the bed. My guess is that this is water from the road that has been picked up and thrown up by the wheels into that region, which is leaking from gaps behind the tail light assembly. This place is full of dirt and water -- opening the tail light assembly, one can see a bunch of dirt and water behind it.

Does anyone have this leak? Any ideas on how to combat this? I imagine mud guard flaps may help, but I'm not sure whether they install beyond this point or not. I'm wondering if there's some sort of plate / tarp / rubber sheet that can be tied to prevent this splashing.

Appreciate your responses.

 

Flex tape. Good idea!

 

I’m guessing the water is blowing along the exterior bed sides, then up and under the plastic bedside cover, and into the bed. I don’t think mud flaps will do much.

I think the plastic bedside covers just pull off (from what I’ve seen with guys switching to OEM bed covers which use a different bedside cap). I doubt there is much of a seal there from the factory.

If you really want as water resistant a seal as possible, I think you’ll need to remove the side rail cap and run a bead of silicone caulk down the length of it.

Same with the power outlet. Remove it, rune a bead around the perimeter, then reinstall.


Just as an aside - I have no experience doing this on my Tacoma, but as a boat owner I’ve done numerous through hull fittings so I understand the challenge.

 

That's a good point, but oh man, I wish there's an easier solution because I don't have the resources handy to lift-off and re-install the Alu-Cab.

 

Yeah unfortunately it's under the plastic bedside caps. I just have a regular old ARE and have the same issue occasionally

 

Set up my Son's 2018 DCLB OR with an ARE and the cap dealership knew exactly how to seal it. Not one drop in almost 3-1/2 years.

 

There are notorious gaps in the front corners of the bed. Toyota has a solution that comes standard with the OEM tonneau cover -- specific rubber plugs for the corners. These are available as parts -- # 6254104010 & 6254204010 -- for about $32 each. Use with plenty of silicone sealant. (You have to slightly modify the side rail caps.)

 

You don't need to lift it off completely. undo the clamps and prop it up from inside the bed. Raise it just enough to get at the side rails then drop it back on the bed. A stack of plastic milk crates will hold the alu-cab up.

 

I just did this for my Alucab Canopy Camper.

Short answer, it took a decent amount of time and some serious forethought to keep all of the water out.

Skip those Toyota tonneau cover plugs. Get yourself Sikaflex from Amazon to really seal up the bed. You will need to seal under the bed rail caps. All the cubbies need to be sealed.

$20 Sika Sikaflex-221 - Black - Multi-purpose polyurethane sealant/adhesive - Creates permanent elastic seal - Sandable/paintable - Non-corrosive - 10.1 fl oz

https://www.amazon.com/Sikaflex-221...1-1-f0029781-b79b-4b60-9cb0-eeda4dea34d6&th=1

You'll also need to seal the tailgate somehow, something I can't lend any advice about as the camper removes the tailgate entirely.

Any other questions let me know.

 

The bed rail caps to come off easily, but that's a nightmare once you already have the cap on there. As heavy as it is, one strong guy (in my friend group, we call him John) can stand in the bed and hold it on his back like a turtle shell long enough to pull the caps.

If you don't have that option, you could seal along the inside edge of the cap, but I'd be concerned about trapping water in there.

Everything I did for my RSI cap:
Removed bed rail caps and sealed with caulk
Butyl tape in the corners
Gasket strip along the side and bottom of the tailgate

 

Check out some posts under the RSI smart cap threads that are on here. https://www.tacomaworld.com/threads/rsi-smartcap-photo-heavy.683746/page-27

 

Update: I realized I never posted the results. Most of my water leaks are gone. I'm sure there are some left, but I haven't camped in the back in the rain, so I don't know for sure where they are and what's causing them. But I did take it to the car wash and did not notice a river in the bed.

I didn't want to use silicone caulk on the bed -- only on the Alu-Cab -- mostly because of reservations about making a mess on a new truck.

Here's what did it for me:
1. FlexTape to seal the two open holes in the front of the bed.
2. After-market mud flaps, which prevents water from the road from splashing into the underside of the bed rails.
3. Some more FlexTape on the underside of the bed rails.

I wish I'd seen this post earlier. Seems like a very useful thing.

 

Here are pictures of the Flex-Taping on the under-side of the bed rails. The strange wiring you see was my abuse of an aftermarket bed-lighting kit to connect my Alu-Cab dome lights to the same circuit as the standard bed light. I eventually plan to transition the lights to a separate battery so that I can have them on all night without the timer kicking in and also not worry about being able to start the truck the next day.

 

I was pretty shocked to see all the potential spots water can get through in the beds of these trucks. Originally, I wanted to use rhino lining and seal the whole bed up. I still feel like I should have done it. All the cubby holes and even to the tail lights it's just open everywhere. I do plan on getting in there once the weather dries up so I can seal it but damn man, Ive never seen so many open spots before.

 

Here’s how I handled the tailgate.

 

Wish i saw this post before installing my Smartcap. Water coming from everywhere except the cap.