I returned from a 2 week vacation and noticed some standing water on the weatherstrip seal when I opened the lift gate. Truck was parked outside the whole time with some heavy rains throughout that 2 weeks -



I pulled back the weatherstrip a bit and found quite a bit of rust. Most of it surface rust but a few bubbles -



(A lot of this is sand not rust.)

The lower belt molding on the rear glass was replaced about a year ago and still looks brand new. I pulled off the lift gate interior cover, and all was dry in there, and the water drains in the lift gate were dry too. I'm assuming the weatherstrip/seal is going bad and perhaps has a crack/leak, and needs to be replaced. I'll scrape off as much of this rust as possible and re-prime over it. $125+ship for new weather strip and see if it stays dry.

This is on a 2010 that is not garage kept. You guys with older 5th gens may want to check this area.

The rear "window rolls down" is so overrated.

How dare you!!! The back window down is the best feature. Other than that, the truck is really a big POS. Let's be honest.

So an update on this. I though it was probably the lift gate seal that was leaking, but upon further inspection I think I may have been getting the slightest water intrusion from a trim clip. When I removed the interior lift gate trim piece, I saw some water stains coming out of a trim clip hole in the body:



Looking at the trim clip for this hole, I noticed the little black washer was missing. Most of the others had it. I did pull this trim cover off about a year ago to replace the lift gate speakers and I guess I didn't notice that the black washer either ripped off or possibly stuck to the body and then fell off.



And Toyota calls this a "trim clip with sealer", so I'm guessing that little black washer is pretty important to seal out any water that may leak into the gate at the rear window.



So I'm assuming that a tiny amount of water slipped through this hole during heavy rains, and leaked down inside the lift gate seal, and caused the rust. I replaced all the trim clips without the black washer (3). I'm sending the gate seal back, and hoping this fixes the issue.

A better pic of which hole it was. It was on the right side.

Having a similar problem. Photos were helpful 👍