Where's my bed leaking?

Last week I began the process of waterproofing the bed. So far I have closed off the cubby and taken off the plastic bed rail caps, put down aluminum tape and silicon, reinstalled the caps, and weighed them down overnight. I still have the front corners to do and around the tailgate but I am still getting a ton of water in the bed all around the sides of the bed and haven't really seen any improvement since doing the plastic caps.

I know I have one weak point in my diamondback where some water is getting in, but it seems like there is water originating behind/beneath the metal tracks on the sides of the bed where toppers are held in place. Has anyone else faced a similar issue or know where the water is coming in from? As far as I know, the only opening in that area is for the torx bolts that hold the tracks, but I can't imagine this amount of water getting through there. I also don't think the water is coming in through from under those plastic caps on the top of the bed or underneath the diamondback because it seems the water isn't on the tops of those plastic caps. Most of the water is below those metal tracks but I can see some water that is puddled on top of those tracks as well.

My next step is to hit it with a hose once it stops raining and dries to see if I can see exactly where it's coming in, but if anyone has any tips or tricks please let me know. I'm getting a new camper installed in the next few weeks and would like to get this buttoned up before then.

 

I'd bet it's coming from between the fenders and bed. The top plate is far from actually sealed. Air pressure from the fenders pushes water right through there.

 

top plate as in the black plastic cap that runs along the length of the top sides on the bed walls? The underside of that should be completely sealed. I applied a very generous amount of silicon in there and taped over the openings as well. Or do you mean another part of the bed?

 

Yeah, that top plate. If you sealed it up, maybe I am wrong. I dunno though, all that water looks like it is seeping from between the fenders and bed though.

Pics lie sometimes, so who knows.

 

Yeah, gotcha. There are some spots where it seems like that's where it's coming and others where it's dry behind but there's water lower down the side of the bed. It's hard for me to imagine the water is getting through there given how I tried to seal it but I guess once it dries and I spray it in different spots I'll get a better idea. Thanks for the reply!

 

I'm getting ready to put a double layer of butyl tape under the bed rails - on the bed side of the weep holes so water can still drain through the holes but not get to the edge by the bed. The butyl tape remains flexible forever so it should maintain the seal as the bed and rails flex. Might work better than a bead of silicone.

 

That's a good thought. I considered it but went with silicon based on other recommendations here. I'm not sure by bed rails will come back off so I don't think there's any going back and changing it for me, but might be able to jam some butyl in the bed side

 

If the top is sealed, more than likely the water intrusion is coming from where the top of the composite bed and the metal fenders mate together.
You’ll need to run a bead of silicone along that joint.

 

I'm a lot farther in this process than you are, as my Alucab is literally water tight to my bed.

You have water seeping in between the rail and the composite bed side. This is not water tight from the factory.

Pull the rails and silicone/Sikaflex the back of them.

 

Have you taken the bed rail channels (where you attach things) all the way off? I don't trust my memory but I swear that will expose a seam between bed / rail / etc. that water may be able to ingress from.

 

That makes a lot of sense. Wasn't sure if there was a gap there but definitely appears to be where the water is originating from. Thanks for the heads up. Now any tips for getting those Torx bolts out if one is stripped?

 

Will look into that next, thanks!

 

since yours is watertight, what other tricky/sneaky areas do I need to look out for? Did you use butyl for the front corners?

 

Did you seal under the rail along the front of the bed by the cab?

 

Put a rubber band over the tip of a slightly oversized Phillips head screwdriver or torx bit, jam it in there and turn. Usually works but not guaranteeing anything.

 

yes, sealed that up but still need to do the front corners between that rail and the sides of the bed

 

Holy crap, op's got a serious sealing issue with his bed cover. Either a bad seal, or something is warped that the cover won't seal.

 

My experience may be a bit different than yours, due to the nature of my build, but here's what I have.

I have no experience with the tailgate, as my Alucab has the tailgate removed. The replacement piece was easy to Sikaflex to the bed.

The front corners have a small piece of dense rubber crammed into the opening (I did not use the OEM Toyota blocks that come with some tonneau covers) and I Sikaflex'ed those into place. I am not sure how your cover flips around, so that may not work for you. My camper is rigid, so cramming something in there was the easiest option.

Due to the use of my interior bed space, I just completely sealed the passenger cubby's, from the inside. 2021 so no drivers cubby. Trying to seal it from the backside was too difficult. I even sealed the inverter cover in place, as I have a legitimate source of AC power already back there.

I loosened the bolts that connect the bed to the frame and put some Sikaflex down there too.