We had few days of heavy rain here in California a week ago and I noticed while cleaning my trunk a small water puddle under the left black plastic tray nearest the left tail light. I traced the source of the leak from the back of the taillight assembly. Curious as to what's causing it, I removed the tail light and was surprised to find a pretty significant amount of mud, leaves, dirts etc. accumulated over the years, fully clogging the path of rain water down to the bottom of car and causing water to seep and find a way into the car's interior. See attached picture. This is a bad design of rain water drain path for this 3rd gen prius. That means 3rd gen owners have to remove and clean the space between the tail lights and chassis every few years else we will end up with flooded trunk. Just sharing the experience...
Is there any gasket around the tail light that might need replaced? I probably need to check this on my Prius as some leaves do collect on it at times (no indications of water inside yet). My left-side hatch inner liner is still out (from replacing traction battery) so I checked. Looks like it has a nice soft easily reusable gasket. Two nuts & the light is free.
Enough of leaves have collected behind and bellow headlight to stop water from flowing out of there. Then water did just get into the car through light assembly gasket.
Open up the hatch. Look at the rain gutters on each side of the hatch. On my Prius as they flow to the rear they disappear under a piece of plastic adjacent to the tail light assembly. When smaller leaves/trash falls into this gutter it can disappear into this trapped cavity area. I have seen leaves disappear & always wondered where they went - seems I just found out. Now to check it - later
Exactly the same problem - water in the trunk and 12V battery compartment. Noticed it when my 12V battery died after cabin light was pushed on and apparently discharged battery to zero, but that is another story. I spend half day disassembling lining, taillights etc trying to fix it. Area behind tail lights black plastic had a lot of pine needles and dirt. Cleaned, assembled and water tested - water still sips in on the right. I noticed black foam on the light assembly which is supposed to make it water tight is not properly centered on the bulb holes. - on the bottom bulb there is not enough material on top curve. I guess after 8 years foam shrank and water now can sip through the slit. Need to replace the foam I guess. Do you know if it can be found separate from expensive light assembly? Another idea it to keep rubber plugs on the bottom open to let the water out. Bad design from Toyota.
The grommets in bottom of 12V battery area are supposed to let water dripping out... I've found water in that area and it has been staying dry after I pull the grommets out and clean it off.. Posted via the PriusChat mobile app.
Perhaps something like this could put in place of factory foam pieces to avoid leak? Universal Seal 1 in. x 1 in. x 12 ft. Impregnated Expanding Open-Cell Foam Sealant Tape-HD-ASR-25-25-04 - The Home Depot https://www.homedepot.com/p/Universal-Seal-1-in-x-1-in-x-12-ft-Impregnated-Expanding-Open-Cell-Foam-Sealant-Tape-HD-ASR-25-25-04/20 Or... M-D 10-ft x 1-1/4-in Black Window Seal Rubber Window Weatherstrip in the Weatherstripping department at Lowes.com https://www.lowes.com/pd/M-D-10-ft-x-1-1-4-in-Black-Window-Seal-Rubber-Window-Weatherstrip/3120623?cm_mmc=shp-_-c-_-prd-_-hdw-_-google-_-lia-_-145-_-weatherstripsoftgoods-_-3120623-_-0&store_code=1071&placeholder=null&gclsrc=aw.ds&&gclid=Cj0KCQjwncT1BRDhARIsAOQF9LkpFJ_qpC9k-2KqmG2NUnYoSub_CqCIWfzpFMXNdlz3AgZOi1Nj1tgaAgZMEALw_wcB Posted via the PriusChat mobile app.
Thanks for waking up this potential problem @rvdbos , I think I'll go check ours. I know some pine needles have snuck in, under the, what do you call the air scoop that runs the full width of the hatch, the name escapes me. Some areas, I've tried "flossing" the problem zones with a length of twine, helps a bit and avoids need to disassemble. Excellent pictures btw.
I'm going to glue in a piece of screen covering the gap between the taillight housing and the body, so that leaves and debris can't get behind the taillight... and see how that goes. On another car, a Lexus CT200h, I filled that gap with silicone.
Photos below. Removed both taillights and ran a length of Gorilla tape to smooth out the irregular nooks and crannies behind the black filler panel. Also tried making a deflector on the taillight housing, using tape. This was not fully successful so for now the gap is going to be closed at the top. Water, leaves etc should now run down the roof rail and over the top of the black filler panel. This is working on the CT200h. .
Kinda ridiculous that this should be needed. Toyota's not alone in this: we've had lots of Honda's that also trapped garbage, turned into a real slime pit.
Untraceable leak in the trunk of a Civic, plus a rear end collision, basically made the decision for me to total a car. It shouldn't be like this. The taillight design is way too complicated inside, and the drainage off the roof rail into anything that can trap debris is an inexplicable design choice.
2009 Prius, had water spots in both rear corners by the tail lights (dripping from above where the plastic piece clips to the carpet). I cleaned both sides of the channel around where the hatchback meets the body and sprayed it with Rustoleum Leak Seal from the top corner to the bottom of the channel. Water continued to leak so I cleaned the top of the channel paying close attention to the 2 rubber boots, soap and water, then rinsed and followed with alcohol spray and compressed air to dry. Sprayed the entire channel with 2 coats and the water continued to leak. So I pulled off the rubber (plastic) trim strips on the roof, cleaned the slot and found several of the spot welds had actually been too hot and had burned several tiny holes in the bottom of the slot. Cleaned, sprayed 2 coats, left the plastic strips off for 2 days to be sure the spray had dried. Took a garden hose and flooded all the sprayed areas and no more leaks!! Hope this helps you Prius owners!! BackyardBob
If the car was rear ended/punched/backed into a tree, bad hair day, astrology sign lined up with the wrong moon, etc.. in the right rear corner and the battery well is flooding, then it may be a weld seam below the tailight, behind the bumper. It didn't look like much of a separation of the seam. Yet if Noah had lived in the battery well, he would be building an ark. He would gather a pair of roaches and some field mice as well as a $hitload of mosquitos and live on. Inside your Prius. I digress. If you are not the original owner of the vehicle and/or cannot validate its history, this is something to check. Maybe the obvious - scuffed or punched in right rear section of the rear bumper. Maybe the not-so-obvious- the rear bumper was replaced. This was the cause of a leak in my 3rd gen. Silicone sealing the tailight did not fix it. This requires removing the rear bumper or at least removing enough fasteners to pull the right side of the bumper away for visual inspection- there's enough flex in the bumper where you dont have to remove it (although you might want to do some rust prevention- a little sanding and some of that truck bedliner spray paint will work ). Water isnt needed. Just use a flashlight. After seeing light from the outside coming through the weldseam, I poked a small electronics screwdriver right through it. Scraped it a little, cleaned it and filled it with JB Weld. Checkmate. No more leak.
