OEM Tonneau leak prevention efforts

hello all!
long time lurker here. joining now because i spent the last several weeks trying to figure out how to eliminate or at least minimize the leaking that is occurring with my oem tonneau. I have read dozens of threads about the subject, but didnt find one centralized tread that concentrated on what specifically people have done or tried to prevent the leaking. most of the helpful things i found were mixed in sporadically in general tonneau threads. admittedly, I'm not the best at defining really good search terms, so if i've missed a thread dedicated to this very premise, please feel free to post a link and i will abandon this one. I have pretty much reached the end of my desire to try and fix the cover i have, and will probably sell mine (however unlike the salesman i dealt with, will be disclosing ahead of time that the cover is not water proof or in my case, barely water resistant). Unless anyone is able to suggest something i havent tried, i will be posting a for sale add as soon as i am permitted per the "for sale rules" sticky. In the meantime, i thought i would start this post to give some one looking for advice a clear path of what works or in my case what doesnt.

 

I have the OEM cover and have found that it does a pretty good job at keeping the bed dry. I only get small amounts of water (tested while driving through some seriously heavy rainfall), such as a small mist towards the front corner, and occasional tiny "runs" (and I mean tiny) of water down the side of the bed, the rest stays dry for the most part -im happy with it.

To answer your question I close my tailgate before shutting the cover and make sure its snapped securely on both sides.

 

So after having spent alot of time reading everything i could find in this and other forums about the 3rd gen tonneau, i realized my expectations of having a waterproof trifold were a bit unrealistic. i had an armor lid on 2006 which is basically identical to Undercover's classic one piece. these obviously have no seems, and cover the bed rails, so i never once had a drop of water in my bed. i had no idea when i bought the 2018 with the OEM trifold, that leaking was even remote possibility. to me, the entire purpose of the cover would be to keep luggage/tools/camping gear/hunting clothes and so on, back there and dry. when my kids sleeping bags turned up soaked on a camping trip, i was beyond dismayed, and thoroughly pissed when the service department told me "it says in the owners manual that they arent meant to be waterproof". as many have previously stated, i have never read an owners manual prior to buying a vehicle, and my salesman never mentioned this obviously. after complaining to Toyota customer service, i received a $1200 credit towards future accessories and services. I really like the OEM cover aside from the leaking part, so i set out to try and fix the leaking issues rather than replacing it with an aftermarket. The first thing i noticed, was that the corners near the cab, did not even meet the rails of the bed. so i thought that this was the sole source of the leaking.

 

So sorry to hear about the kiddos sleeping bags! I can understand your frustration.

My cover also lifts slightly I the front corners as well -i think this is why I get the misting at the front. Not sure if there is a better solution? I think I remember seeing someone apply weather stripping attached around the bed of the truck. You could apply it so that the cover sits "on the outside" of the strip which might help prevent water leaking in? Just a thought

 

you know BSFord, this is what confuses me. first of all, nice to meet you, and thanks for your input. it realy does seem like it is split right down the middle. half of the OEM owners do not have much if any of a leaking problem. and half do. some, like in my case, the leaking is excessive. these were taking initially when i was trying to illustrate the issue to the service department. these puddles are by no means the most amoutn of water that i had leak in. we've had some good rains here in Pa lately and i have had the entire bed wet, just didnt get pictures of it.

 

thanks again. i have already done this as i will document here shortly. just breaking up the posts a bit so i dont wind up writing a single novella post. lol.

 

Just saying, but I don't get that much water coming in after running through a car wash with my cheap roll up tonneau, let alone the typical rain here. For a pricey OEM design, that is unacceptable.

I keep meaning to seal up the front rail gaps. It looks like your front panel is sitting a bit high? What I did do, thinking that I could level out the front rail with the side rails, was take off the front rail in hope of slotting the mounting holes a bit. I found that the rail just sits on top of the front wall with some foam sealing tape. I peeled that off and used some silicone caulk. It was a minor improvement that might help you lower it a scosche?

 

In for possible solutions. Mine leaks a little from the fold seals but a lot in other spots. I haven't really had a lot of time to look at it but want to. I do think some of it is coming in under the plastic bed rail cap. I want to pop them off and put some foam sealant in there to see if that helps. I did add a tail gate seal and that seemed to help with dust getting in.

 

The side rails snap tight. I had one off to do a difficult version of the rear diff breather mod:



Adding foam might be too thick? What gets tossed around is to use metallic sealing tape to cover as many holes as possible and then use some silicone caulk as a seal. This is usually done to keep the rails from wearing on the painted surface when using a canopy and was more of a problem for the 2nd Gens.

That said, I don't see much if any water getting in under the side rails.

 

So after the service department told me there was no way to adjust the cover, i looked at it a little closer and decided that i could make it tighter. before anyone mentions it, I do know about the double click on the latches, the above pictures were after the double clicks. i decided to alter the latch post by turning it upside down, and drilling new holes. the post i am talking about is in the red tacoma picture. that is not my picture, i found it on this forum but i dont know who to give credit to. and that picture is not of the part after i altered it. sorry i didnt take a picture. but essentially what this did was pull down the cover 1/4" or so which then appeared to seal it up. no more light came through when i looked under the cover.
I also had to shorten the cylinder on the other side, that the security bolt passes through. the picture of that assembly is again, not after i trimmed it, this is how it looked originally.
the

 

Thanks Age and tonered. after i was successful at pulling my corners down, i still noticed water coming in from the area around the bed rails. the whole legnth of the bed had streams of water running down the side. so i too deduced that water was getting under the rails and popped them off and siliconed the entire length of the bed. this seemed to help on the bulkhead rail. i didnt notice any more water getting under that. but i still noticed the same water streaks on the side rails, so i guessed that there wasnt any water actually getting under the rails, it must have been coming from somewhere else.

 

oops...i skipped a step. before any of the above attemps. the first thing i did was pull apart the latch next to cab on the driver side and removed the spacer that was underneath. this had minimal effect, and actually caused the latch to have some trouble latching as the spacer actually provides some clearance for the working parts of the latch. without, the moving part of the latch was too tight to the cover to move freely. sorry, no picture.

 

Strange, The cylinder spacer for the bolt on mine was too long as well. Grinding it down a little helped make the front seal ...Not sure why they made it so long, it defiantly made the front pop up and not seal.

 

Thanks sandtaco...i tried grinding it, and decided it was more efficient to saw the end off with a reciprocating saw. not saying it was the correct decision...just documenting my own thought process.

 

OK, so now i have fiddled with the latch to no avail, successfully pulled both corners next to the cab down tight, and siliconed under my bed rails...also siliconed the gap between the bulkhead rail and the side rails. still had just as much water getting in. I then took a closer look at the bedrails, and decided that the texturing (the little raised dots and tracks) must be preventing the seal on the cover from actually sealing properly. like if the rail was smooth, it would seal better. so the next thing i did was run a 1/4" bead of black silicone down the legthn of the bed rail. i marked exactly where the seal of the cover would meet the rail, and center the bead so instead of meeting the rail, the seal would meet the bead of silicone. I was super high on this idea, but i never actually got to test it. i let the silicone set up for 24hrs before i put the cover back on. after having the cover back on overnight, i had to open it and as you can imagine, the silicone all came up with the cover. I though about trying butyl tape next, or letting the silcone cure for a few days, but decided that it probably would have the same effect and decided that even if i was able to get it last a little longer before pulling up, did i really want to be periodically reapplying silicone or butyl for the next 300k miles?

 

In my pic above, you can see the extrusion used for my roll up tonneau. It is held down in only three spots and has a thin foam tape on the bottom. Some nice, conforming stuff, but it isn't very thick. I can't imagine that it seals as well as the rubber gasket on your trifold? There shouldn't be an significant airflow under there to blow the water upward. Do you have wetness on the cover above the level of the seal? I am wondering if your cover is leaking at the trifold joints or possibly some other manufacturing defect?

It might be worth getting in the bed with some good lighting and with the tailgate closed. Then have someone hose down the tonneau to see where the water is coming from?

 

my final attempt was to search out some weather stripping as BSFord mentioned earlier. I used this stuff from home depot https://www.homedepot.com/p/M-D-Bui...-Auto-and-Marine-Weatherstrip-01033/100175299 . I placed it on the bed rail exactly where the seal of the cover would meet. unfortunately not two days later, i was again disappointed when i looked in during a moderate rain, to see the same streaks of water running down the sides of the bed. It didn't seem to be as bad as it was though, so i guess this helped to a degree. but still more than i would call acceptable. as others have suggested on here, i though about getting the bed mat and hoping that keeps my contents above the water, but as you can kind of see in the second two pictures that i posted, there is actually water dripping in the middle of the bed, so the hope of the water running down the sides and under the mat doesn't apply.

 

one step ahead tonered. i was about to run out and grab a picture to help illustrate my next post.

 

last night we had steady (but not heavy) rain. as tonered mentioned, i did in fact crawl insider the bed with flashlight and looked around for more infiltration points. i saw water dripping in everywhere two panels met. not so much in the middle of the bed, just along the rails. so i am now satisfied that i have identified all the points where water can get in, but i have no desire to try and engineer a fix for the joints leaking. if anyone else has somehow managed to fix these areas of concern, i would be all ears.