Mildew under rear passenger carpet

Hello I've had the "water leak in 12v battery compartment" in my 2005 Prius. I've noticed it only last summer and it is now FIXED (for me at least)

Here is what I did:

I've removed all the cover inside the car and looked where it was coming from. It looked to be coming near the cylinder that holds the hatch open... it was VERY difficult to find ... but it is a "spot weld" (or maybe welding spot sorry my english is not perfect) that was not watertight enough. The thing I did was to put some silicone sealant over that spot welding thing and it FIXED my problem. NO MORE WATER in my battery compartement. Tested after a complete autumn and winter .

See one of your pic I've borrowed... I've put a green mark where I recall it was leaking. I think the spot weld is just under the cylinder... I'll do my best to take some pics on my own Prius tonight.

 

Thanks a lot ... your answer is really helpful and encouraging ... That was the point I first suspected, but then I said it's improbable to be that one. Now, with your confirmation, I'll check better tomorrow morning, both the right and left sides. Thanks again!

 

I've said improbable myself a lot...in fact I cannot see it with my bare eyes, I mean the crack itself. Then I called my dad to come and double check everything with me (since half of the back of the Prius was dismantled and I wanted a second person to confirm) and he agreed with me. We could reproduce the leak with water running on top of that spot. We then put some silicone and could NOT reproduce the leak.

Since then, at least 6 months, I've checked two times and NO leaks.

For me it was the passenger side only but I did do the "test" on the driver side welding spot... but no leak ...

I'll put pics when I get home... in approx. 4 hours.. still at work

 

Pics are in

NOTE: It's not guaranteed to work for everyone but I confirm it worked 100% in my case for water leaks in the 12 volts battery compartment. (2005 Prius).

First one is passenger side where you can see the silicone stuff. I know, it's not really "nice and smooth" but it works really well.


Pic no.2 it's the driver side with NO stuff but where you can see in green the source of the problem. Right in center you can see the spot welding.

 

Syco:

Thats a really good find. And that's probablys the OP's leak area too as it must be high on the body given how so much of the upper interior is wet.

The Mighty Putty I mentioned would have worked perfect there as all you would need is a tiny bit to fill the weld dimple and it can be smoothed out in the channel so it does not obstruct water flow and then painted to match.

 

Mighty Putty, yes but for me when seen "live" it's not that bad and it is not much thicker then a quarter ( or maybe a dime) so it does not obstruct water flow at all.

Thanks for your tip and comments! We will see about OP soon maybe

 

Hi. Looks like you've likely got the source of the leak figures out.

I'd just like to point out that silicon sealant in contact with metal can really promote and accelerate corrosion. So maybe the putty that Ed suggests is a better idea.

 

Ok. So yesterday I spent the day "siliconning" everything (I didn't know about corrosion promoting) I suspected it could be a possible way for the water to go in. Plus i tried to put some kind of barrier to stop it from going in front. Now I am awaiting for a rainy day to see if my work was in vain or not. I will keep you updated.

 

Update! Two nights ago it rained a lot (I'm in Baltimore now) so my car got exposed to a lot of water. It seems that there was no water leaking inside ... anywhere it used to. So, I hope I fixed the problem and I hope the fix will last.

 

Good to know I'm pretty sure it will do.

Just for information I have used Kleen-flo 470 Gasket Black. I'm not sure about corrosion but it was applied over the paint and I did not noticed any rust where I've used it.

 

I have this problem on ’04 Gen II and have just found the main water ingress point. Once the sealer I applied dries I will spray it again with water to see if any more smaller leaks are there. This is the text I posted on a UK forum (where I live and write a different sort of English! We call "trunks" "boots".):-

By taking off (3 screws/bolts and some clips) the upper and lower trim at left side
of boot and round the rear small window (beware there seem to be 2 airbags in that
area) I could see it's all sodden behind and some of the trim was sodden too. An
external easy to see clue to damp is condensation in the rear light cluster. The
water in spare wheel well comes from the side well when it gets full. The
courtesy light had water in it but mine is still working (one person reported his failed due to water). Just above it on
inside of trim there was an obvious spot where water was dripping on it from
metalwork above.

By applying a hose to the gutter down the side of tailgate, with tailgate open, I
could find the leak. It did not start leaking till I reached the very top of
tailgate opening, so it is coming in there but tracking down inside the box section till it
reaches above the light, although a little did come out at top too, near an
“airbag”.

The culprit was found by lifting the rubber strip that fills the roof gutter
(where a roof rack can go). Under the rear clip for this strip (beware one clip
broke in cold weather as plastic fairly brittle) is an overlapping seam between the roof and
side panels. The seam is filled with mastic and painted over but mine had a 2”
hairline crack along the mastic. The crack is too narrow to fill with new mastic so
I used touch up paint, warmed up to penetrate the gap. A wax based sealer like Waxoyl
would have been better as more flexible than paint and penetrates well and so cuts any further rusting that may be in the seam.(Don't think Mighty Putty would work as too rigid when set and too viscous when not.)

On the right side there was a smaller crack but I have no recent experience of damp on
that side. The battery well did fill up a long time back but I put it down to
water from wheel well slopping over so could have originated on left side.
I permanently removed a drain plug under battery to
drain any more leaking. So I would no know if it has still been coming in
recently unless the trim got wet.

Also worth tightening up the tailgate gas strut mountings as is if too loose water
might come in there.

 

Guys last couple if weeks noticed the identical conditions. Found the A/C rubber adapter disconnected from the drain pipe. See picture below. This was leaking thru the front carpet and ironically it was not wet! The right rear soaked! This was my culprit. Anyhow, I will tie wrap both ends and it should not happen again.

 

I started digging into my trunk today to check the age on my 12V battery, to see if maybe I should replace it before I get caught with a dead one (it's a 2008 manufactured in 11/07 and, as I suspected, it's still the original battery). I'm glad I checked, because what I found first was the spare tire and battery compartments flooded with about 3 gallons of water. Looked on here and the other "water in spare tire area" thread mentioned above and read about this problem so many are having. I removed the black plastic trim from the right (passenger side) edge of the roof and, after careful examination, found the crack shown in the photos I have attached here. I haven't sealed the crack yet, but I feel pretty good about my chances of success, now that I read here about what is going on. Thanks to all who posted on this! I'll report later on my fix with the leak.

One thing I will mention is that I had the spare tire out a few months ago and there was no sign of water in there then. I've never seen water in there before (but never looked around the battery until today, either). In October I did buy a bike rack and hauled our two bikes around a few times. I am wondering if this triggered the problem. Wondering if anyone else had done anything similar before their problems started. Also had been wondering why the windows were so bad to fog over so fast anytime the a/c compressor was turned off. Maybe all this water explains why.

 

Yes please report if you fix the leak. I'm pretty sure also that all that water was causing the fog.

 

Good one 90miler.

Since this first post OP many reports of the crack also below yours where the quarter panel connects to the the roof right there at the hinge. Its welded and puttied there and gets a hairline crack. I suspect yours is a variation of it with the crack possibly starting there at that seam then extending forward.

Since these cracks are not epidemic in that we all have this problem I can only surmise they may be caused by trauma possibly by repeated slamming of the hatch without a door open (to vent cabin pressure) or driving the car on very rough roads with hyper inflated tires.

Hate to think the extra small weight on the back from the bikes caused this but something to think about.
Btw, they sell the special bondo type crack sealer they use at the factory specially for this issue. Don't use silicone.

And the fog was coming from the swimming pool in the trunk.

 

I had the same problem along the metal seams along the back and by the taillights (on the metal seams not the tail lights). I think I fixed with silicone, but it gave me a very bad impression of Toyota for sure.