A Look Into Why Your Trail Edition Lockable Bed Storage Boxes Might Leak and a Fix

So I just picked up a set of boxes (brand new take-offs). Finally, my CM has some storage and I can still mount my bikes to the front rail or haul the kayak. Prior to install, I made a few observations that I would like to share with ya'll to provide some insight as to why your boxes might leak. Don't be discouraged as we can address this. Why should you even have to, you ask? I don't know, but here is a solution after I explain a few things. Don't care? Scroll past the pics for the fix.

First off, here's more of a disclaimer or common sense. It doesn't matter if you agree with it or not, but some version of this will be the voice of reason. So, I'll just get it out of the way. Toyota didn't intend for you to drive underwater or actually through a hurricane. Normal precipitaition that doesn't actually damage any vehicle or structure generally falls downward or at a slight angle without much force (unless you live in Oklahoma) . I've even had dealerships recommended against going through high pressure car washes, especially if you have a sun roof. Silly, I know. Now since that's out of the way, let's get to how they're constructed.

The boxes aren't just a single piece of blow mold injected plastic. Each box is constructed of two major halves riveted together. The seams are theoretically "sheltered" by the walls of the bed. The bed side caps and rails theoretically provide an "awning" for the top of each box. The door opens downward via a piano hinge that is riveted to the bottom of the door and opening. The door lock striker is mounted internally at a downward angle. The door lock is mounted to the door in a bulkhead fitting fashion with a steel backing plate on the interior and sealed trim ring on the exterior. Weatherstripping is affixed to the interior side of each door continuously along the top and side perimeter. On the driver side (which doubles as a cooler...yes, it's heavier than the passenger side), there's a second weatherstrip just above the piano hinge. Because of the weatherstripping, each door has to be pressed closed with pressure until you hear the audible click. There's two drain plug grommets on the bottom per box...one in the front and one in the back. Blah, blah, blah... Great, so what's wrong?

Only the bottom and vertical seams have a bead of sealant applied between the halves prior to being riveted together. And the consistency of the bead depends on the skill of the person at the factory with the caulking gun. The top riveted seam has no sealant all and relies solely on the concept that it is recessed into and sheltered by the bed side top cap and rail. There's actually an air gap in the top forward and rear corners. Why? My guess is that it might serve as a breather. The box is black and sits in an open bed under the sun. As the air inside heats up, it expands. I guess the gaps would let the air pressure equalize to prevent your box from bulging and deforming as temperature, elevation, barometric pressure, etc changes. Also, moisture might build up inside as a result of condensation. Have you ever opened a sealed plastic 55 gallon drum to find moisture inside? The air gaps might let this moisture evaporate so mold doesn't form. Your cab has breather vents too.

Below are a few pictures that I took to identify where your boxes might leak water. All of these pictures are of the passenger side box. Both boxes are similar in construction other than what I have already stated.


Here's my suggested fix (other than installing a compatible soft tonneau cover).
Remove the boxes.
Each box is secured with:
.1 bed utility rail
..5 T30 M6 x 1.00mm x 25mm pan head screws
..5 20mm OD x 8mm ID x 5mm spacers
.1 rear tie down
..2 T40 M8 x 1.25mm x 25mm cap head SEMS bolts
..2 M8 x 30mm OD fender washers
..2 M8 x 15mm OD x 5mm spacers
.inside the box at the forward tie down lower hole
..1 T40 M8 x 1.25mm x 25mm cap head SEMS bolt
..1 M8 x 30mm OD fender washer
..1 M8 x 15mm OD x 5mm spacer
Note: Don't damage or loose the hardware. The part numbers aren't listed yet. The bolts used to install the boxes at the factory are indeed longer than the rails and tie downs without the boxes.
Prep surfaces along the seams with isopropyl alcohol to remove residual grease, oil, dirt, and plastic mold release agent.
Wipe clean and let dry.
Apply a bead of flex seal or silicone caulking to the riveted seams internally and externally, excluding the air gaps.
Cut 4 pieces of 1/4 ID vacuum hose approximately 4-6 inches in length.
Place a hose flat against the box with one end of the hose at the gap with the other end facing down.
Note: Gorilla weatherproof tape adheres strongly to surfaces. Attempted removal will damage tape. If a mistake is made and tape removal is necessary to adjust alignment, discard tape and use a fresh piece. Carefully secure hose in place with Gorilla weatherproof tape, covering the entire length of the gap with a continuous piece of tape.
Hint: The tape will serve as the flashing while holding the tube in place. The hose will serve as the breather. Using the Gorilla weatherproof tape to seal the entire seam is not recommended as the edges of the tape remain tacky. In addition, the thickness of the tape may cause misalignment of the box on re-installation.
Re-install the boxes.
Using a T-40 Torx driver, bolt down box using OE tie-down loop and the M8 bolts.
Torque: 17.5 N·m (13 ft·lbf)

If all else fails, I seen some weatherproof cases at HF that would go nicely inside these storage boxes. Hope this helps.

 

interesting, just installed mine and may have to do this when the I have time again.

 

How watertight is the door? From the pictures I saw it didnt appear to have a raised edge around the opening to deflect water. Poor design IMO. they should have known people would want things to stay dry in there.

 

Did this work? Mine leak like a sieve.

It's a terribly poor design. The dealership says, "It's meant to leak. That's why it has drain holes in the bottom."

 

They are not meant to leak, mine haven't leaked. Plenty of rain here too.

 

Well, first thing...I don't believe anything any dealership says...period. Besides, who at the dealership said this...a sales associate, a service manager, a mechanic, a parts specialist...? I'm sure they're all subject matter experts and represent the views and opinions of every Toyota dealership as well as those of Toyota Motors USA right? Take their opinions with a grain of salt...cause you know everyone has one. Surprisingly enough, not too many people around here know about these boxes. I get asked about them all the time. The folks at Bass Pro Shops know more about them, LOL. More food for thought...I bet every Toyota dealership will tell you that the TRD Pro Fox shocks aren't rebuildable either. Most of them would order the wrong ones anyway. BTW, my dealership marks my brakepads in the yellow at 70% thickness. Don't believe everything you hear.

Yes, the boxes do have drain plugs in the event that they do collect moisture or you need to rinse them out. The driver side doubles as a cooler as well, so the drain plugs allow you to drain the ice water.
As you can see in my writeup, the sealant was poorly applied during assembly. After my improvements, I've had no leak issues with light rain. I also have a soft tonneau cover so I don't have to worry about heavy downpours and washes. However, I don't believe the boxes were designed to withstand high pressure water jets from a car wash or pressure washer. Believe it or not, most sunroofs aren't either; if you removed your headliner and trim, you would find drain hoses that divert water that infiltrates the seals.
There's weatherstripping on the lids, so it's hard for me to believe that they are meant to leak. Unfortunately, they didn't mold a ridge in the opening to divert water...so they are only water resistant to an extent. Yes, they could've been designed better. If you have items that absolutely can't get wet, Harbor Freight sells Apache cases in various sizes.

 

The service rep said the tech said that.

I don't see how water is getting into the places you sealed during a normal rain, but I'm planning to pull them out and seal up everything except the lid and the drain holes. In the meantime I'm oiling my rusted tools and putting them in waterproof bags.