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E46Driver330Ci

Water entering trunk

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Hey people,

I have been afflicted with an impossibly perplexing water leak problem that I have finally found after taking out the trims from the boot. Water was going into the battery compartment as well as into the spare wheel well. Water was accumulating inside the pictured body part and flowing out through boot-side vent holes when full while the car wasn't driven. Water also spilled out of the same holes when the car was driven. The car's movement caused the water to slosh around and then came out.

I am 99.9% sure the water didn't enter the cavity in that body part from inside the boot. I am guessing the water entered from somewhere behind the rear bumper. This time of year makes it unappealing for me to take the bumper off and work on the problem since I don't have a usable garage. I am wondering if anyone is very familiar with that part of the car to be able to make a more precise guess on the possible location of the water entry? Of course, any clever ideas on how I can tackle this problem are also welcome.

The ideas I have are: 1, locate the water entry point and seal it with silicone sealant. 2, seal the inside vent holes to stop water coming in. But I am reluctant to do that without knowing where else the water could go. 3, drill a hole into the cavity from outside to allow the water to drain. There may well be a factory drain hole already but blocked.

Thanks.

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Managed to find the likely drain holes from internet pictures. One is next to the plastic vent in the battery compartment. A similar drain also exists on the other side of the car. It's not clear what these drains are for on a coupe. I am guessing water is draining from somewhere on the roof. Because the drains are blocked, the water overflows into the boot area.

The overflow appears to be a design feature. Same also happens for convertibles. When the drains for the soft-top are blocked, the water goes into the battery compartment.

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Edited by E46Driver330Ci

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Thank you for sharing this. 

It's not something I've read about before but will keep in mind. 

Many thanks and kind regards 

Kirkynut 

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It turned out my car didn't have drains. The cavity where the water accumulated looked to be a dead space. It remained an impossible mystery how the water got in there. I could find evidence of water coming out from it because of water marks. There's no evidence on the boot side how the water got in there.

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I may have to drill a hole from the outside and risk rust. With the water going in there, there is risk of rust anyway. So the choice is between rust and rust. The cavity has no road dirt in it, which suggests it's not really open to the outside.

I have assessed the supposed drains by taking out the vent cover in the battery compartment and looked and felt around that area. There's nothing there.

For now, I am keeping observation and leaving all the trims off. The water had gone, I guess it leaked out from micro seams in the welding. If the water comes back from more rain, I will have no option but to take the bumper off.

 

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A few years ago, upon carrying out an Inspection II on my Touring, the local bmw indy informed me that there was 1/2 inch of water sloshing around the spare wheel. They said to get to the source of the problem they'd have to strip the internal lining in the cabin to start their trace. An easier and cheaper option for me (they suggested) was to just remove the plug in the spare wheel compartment (which they did for me).

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Edited by De Sisti
Context

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Can you explain how that plug works? I have that metal "plug" in the wheel well and in the battery compartment. The only way I can see opening them up is by drilling. Opening the plug has disadvantages: noise, dirt, rust, and the water will continue to do damage elsewhere. It will certainly kill the battery.

I think I might have found the problem, although not completely sure yet. After removing the tail light, I noticed some hairline cracks on the lower horizontal plate. Temperature changes may change the crack size. Underneath that plate is hidden. If water does come through there, then it will never be detectable. Out of curiosity, I took off the light on the other side, same cracks. To me, it seems implausible for that to be a coincidence. I see that as a "design" feature to kill the car, because both the water entry and the exit into the car are very well designed to be hidden. Anyway, I have used bathroom sealant on the cracks. Hopefully, that will be the end of it. What I need now are some heavy rains.

While I was playing with the light units, one had a small amount of water in it. Turned out the the seal of the lens had started to fail. Sealed that with the silicone - should be good for another 100k miles.

Nothing to do now but wait for the appearance or non-appearance of water in that cavity. I have a mini bulb that I can drop into it for quick inspections.

Edited by E46Driver330Ci

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I think it the plug is thought into the design of the car,  just in case the spare wheel compartment fills with water, it offers an outlet

for it to go. In over four years I have not noticed the disadvantages you speak of (noise/rust/dirt/water ingress**). It has always felt

dry when I have carried out a "touch test"* after a heavy downpour. They prised it with the edge of a screwdriver. It is easily put back

in place if necessary. 

 

* Rub hands and fingers around spare wheel compartment for sighs of dampness.

** Water ingress would take path of least resistance (by aid of gravity) and just flow back out again.

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Maybe I don't have a plug then. What I have resembles that circle thing in the top left corner of your picture. It looks like rough metal with a "+" in the middle.

Yes, it's dry if the water flows out. But the water would be pooling somewhere before it flows into the wheel well. In my case, I know exactly where the water is. Even removing the plug won't help because the water is inside the body panel I have shown. The water only flows out when the cavity is filled or when sloshing around.

I'll see if the water comes back after today's fix. But there's no rain just when I need it.

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On 17/11/2019 at 21:18, E46Driver330Ci said:
Quote

Maybe I don't have a plug then. What I have resembles that circle thing in the top left corner of your picture. It looks like rough metal with a "+" in the middle.

Yes, what you see in the picture (to the left of the hole) is what I refer to as a plug. Even after heavy rain I have yet to feel even the faintest hint of moisture where the spare wheel sits. 

 

Edited by De Sisti
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OK, looks like the leak was fixed. It's remarkable how long one needs to wait for rain in the UK. Not much of it but enough to conclude the test. The leak was from hair line cracks on the lower horizontal plate of the tail light recess. That plate was welded and plastered over with some kind of plaster. That plaster did not have the performance to withstand the temperature changes possibly because of ageing and hairline cracks opened up allowing water to seep in. It took extensive rain for the water to build up in the body panel for it to spill out. Because I always reverse out of my driveway to the left, the water mostly spilled out on the right and into the battery compartment. If the car wasn't driven, the water would have overflowed into the wheel well because the lowest hole in the body panel was nearest to the wheel well. I could see water/scale mark below that hole.

Edited by E46Driver330Ci

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On 17/11/2019 at 18:33, E46Driver330Ci said:

Can you explain how that plug works? I have that metal "plug" in the wheel well and in the battery compartment. The only way I can see opening them up is by drilling. Opening the plug has disadvantages: noise, dirt, rust, and the water will continue to do damage elsewhere. It will certainly kill the battery.

I think I might have found the problem, although not completely sure yet. After removing the tail light, I noticed some hairline cracks on the lower horizontal plate. Temperature changes may change the crack size. Underneath that plate is hidden. If water does come through there, then it will never be detectable. Out of curiosity, I took off the light on the other side, same cracks. To me, it seems implausible for that to be a coincidence. I see that as a "design" feature to kill the car, because both the water entry and the exit into the car are very well designed to be hidden. Anyway, I have used bathroom sealant on the cracks. Hopefully, that will be the end of it. What I need now are some heavy rains.

While I was playing with the light units, one had a small amount of water in it. Turned out the the seal of the lens had started to fail. Sealed that with the silicone - should be good for another 100k miles.

Nothing to do now but wait for the appearance or non-appearance of water in that cavity. I have a mini bulb that I can drop into it for quick inspections.

My near side rear light cracked as well and filled with water. Doing my boot refresh this month and will be looking for the same issue. Thanks for detailing this. 

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