I was cleaning out the "belly" of the Prius today and found standing water in the spare tire area and the left rear bottom area, which would be the same area the 12V battery sits on the right hand side. So I am wondering where this leak is coming from? I inspected the hatch weather stripping, the glass sealing, etc and found no issues. Could the driver's side tail light be allowing water in if a seal is damaged? Also..the water turned the rubberized coating where the spare tire sits into fragments. Should I remove it all with a putty knife and brush some undercoating on, or just leave it be?
Just leave it off back there if you want to scrape it up and do that and lay down something similar they make roofing tar that's in a silverback pad and it looks similar to the stuff you're using now you can heat it with the heat gun lay it down and leave the silver on top of it so it won't look like this looks now
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As a matter of fact your rear tail light is a very good call I just took the blacked out '04 '05 type tail lights and put them in my '09 and my 209 tail lights you could see where the gasket was not making good contact it had let dirt and air mixed with dirt in over the years into the car into that area of the well you could even see it on the carpet of the little piece that goes back there that covers the battery or the little cubby hole I put a good bead of real silicone caulk and allowed it to skin before I offered up the tail light and I noticed the tail light stood out from the car body a noticeable little bit 16th of an inch or so until the nuts went on and pulled it so I feel like I got a good gasket seal now I'm running water down that side of the long gasket from the roof all the way down the tail light and I can just run gallons a minute it just comes out of this little slotted piece of hose I have that I can stick right in the gasket and let it run down Not through the gasket just lay it on top of it and my hands are free so I can open the back door and stand there and look at that whole area while this water is just dropping down. I got nothing on either side so I think I'm pretty good shape
There's lots of threads on PriusChat about these leaks. Main source is the roof seams leaking underneath the black trim strips on the roof.
I think I may have identified one leak. Up at the top of the hatch opening, where these seams meat, you can see some rust which looks a bit like water intrusion.
Been working on filling stress cracks I found today. Going to sand down the epoxy and put a little red paint on it. I also re-did the spare tire well.
Happy to report after a couple nights of hard rain, rear area of the car was dry as a bone. I sanded and painted the area I fixed, it doesn't match well, but better than the ugly black glue. I found some rust near the opener for the hatch, I brush painted this area, didn't turn out that good due to using a cheap brush, but no one sees it once covered with trim. Another small piece of sheet metal had heavily rusted from the water leaking, I sanded and primed it as well.
Looks good. The 12 volt battery well is full of water too. Take the battery out and do your thing there too. It’s got a rubber drain plug in the bottom of the well. Drill a small weep hole in it. As far as the hatch corners that’s a good start. Those long thin black plastic strips on each side of the roof pop right off just yank them. You will see more hair line cracks running up those strip valleys.
