2010 Prius - water leak into spare tire well

If you lift up the hat seal a little bit they're up around the shocks and up around across the top you may see some cracking in the putty or whatever the stuff is that Toyota uses to fill around where all these welds are done . You see some of it in the floorboards underneath the carpet etc etc In the trunk you'll see it If you hit it with a hammer it breaks up cracks because it's all dry and brittle You have something similar running around the hatch where the lip for the seal is welded on or pin welded in place whatever sometimes that stuff will get to cracking You can literally see it It looks like cracked paint but that's not what it is water can in grass through those little cracks drip into the trunk area generally right on top of the battery usually or right at the trailing edge of the top of the battery which is towards the back of the trunk water will hit that run down pool in the well sometimes it gets over on the battery side too the 12 volt fills that well up freezes and kills your 12 volt happens all the time I drilled extra holes small ones near where my 12 volt sits because their place where it can pool I also removed a rubber plug on the 12 volt side now I never see any water In that area anymore The first year I had the car like a month after I bought it I lifted up the cover for the 12 volt and saw it sitting almost in a brick of ice well that was no good.

 

Have you pulled off the black rubber strips running the length of the roof? IIRC there were reports of leaks there.

Also leaves can get in behind brake lights, possibly divert water in.

 

Did you check for a deeper water puddle in the corner near the lead-acid battery? Rainwater off the roof and hatch will run into that corner of the interior when the drain passage between taillight and body sheet metal clogs. I had to remove the taillight to unclog mine.

 

My 2010 Prius IV has a water leak. I have partly removed the tail light twice and put a thick bead of silicon caulk on the foam rubber seal which encircles the 2 tail light bulb holes. It still leaks and water comes from between 2 layers of sheet metal. There is no water seen around the tail light seal. The nplacement of the water hose eliminates cracks in the roof and cracks at the lift strut mounting. The last photo shows the water stream passing into the gap at tail light housing. The 2nd photo shows where one leak is and the 1st photo, a different place where water comes in. Note: I did not completely remove the tail light, but I leaned it back to apply the caulk. Totally removing the tail light seemed to be an all day job. (There is a mounting screw behind the bumper guard).

 

AND? All I do for this is look under my spare tire right under where the battery pack is in the well where the spare tire lays lift it up see the rubber plug that sits right on the backside of the battery if you will push that through it falls on the ground pick it back up throw it in the spare tire well and leave it sitting there now when water comes in through any of these places you're talking about it's going to run down in the spare tire well run through that hole you just created by pushing the plug out and the water will what? Pass through the chassis so it doesn't sit and create a terrarium and a bunch of humidity in the car turn your bus bars and your nuts frosted and black on your big battery and all this kind of stuff. Then if you look on each side of the trunk well one place where the 12 volt goes and the other place where the little fancy storage bin is If you lift the battery and the storage bin out you will see some rubber plugs they need to be pushed through You may not find those they're going to go whatever or you can pull them through with a pair of needle nose throw them in the trunk well those are passed through holes for those side wing areas where water will collect I even drilled a few extra quarter inch holes in strategic places where with you pour water you'll see it nest I drilled a hole where it nested now that water all passes through anytime it gets in I don't care where it comes in as long as it passes through. You just don't want the water sitting personally I don't care if it comes in I just needed to go through not sit If you get it to pass through and not sit you'll win the game.