Water leak in trunk

[mcbanan]

Hi guys! Been lurking the forums for some time, lots of good DIYs and information on here

But now I have a problem that requiered me to register, since I could not find the solution to my problem her, or on other forums.

I have a waterleak in my trunk, that has been a pain in the ass ever since i bought the car earlier this year. Water pools under the passenger side taillight area, and on the shelf above the battery. And finds its way from there to the battery compartment and spare wheel compartment.

First I thought it was the taillight gasket, as often is the case. So i changed the gaskets on both sides to be sure. But the problem did not go away.
So I put some silicone around the gasket to help seal it, but that did not help either.

When i remove the bulb-assembly on the passenger side, i can´t see any water intrusion and there is no water in the taillight itself.

Taillights are original hella pre-facelifts.

What other places can the water come from, and what can I do to figure this out?

Edit: It´s a sedan btw, 2000 MY.

[Qsilver7]

Is there an air vent in the e39 sedan's rear fender area like on the e38?

The vent pictured above has flaps that open close based on air pressure inside the car. If you have these vents, make sure that the flaps close and that there's not access for water infiltration behind the rear wheel well liner and the interior fender.

How about the battery vent tube? Is it and the grommet that surrounds the vent tube in place to prevent water infiltration?

{battery vent tube & grommet}

[mcbanan]

Hi! Thank you for your suggestions, the e39 does have these vents and a battery vent tube, but they are too low to be the source of my leak.
I don´t have a sunroof either, so it can´t be a broken drain pipe.

[JimLev]

How's the seal around the trunk look?
Have a friend get in the trunk and you soak the outside with a garden hose.

[mcbanan]

Looks pretty good, no rips or tares. I tried that earlier this summer, but of course that was the one time no water came through I should try it again though, probably the best way to figure it out.

[philly98540]

My trunk lid gasket leaked a tiny bit a few years back. Gasket looked perfect but would leak where it was pressed onto the metal lip it gets pressed on to. I fixed by putting some black RTV in the groove of the gasket then reinstalling it.

[mcbanan]

Thanks Philly, I´ll check the gasket better just to be sure.

I managed to lure the girlfriend out with me to pressurewash the car. So I got in the trunk, with a flashlight, and she sprayed the car for at least 5 minutes.

Not as much as a drop appeared in the trunk. Very typical.

BUT after a 10 minute drive I checked again. There was now water on the shelf above the battery, but not under the taillight. And since I always have paper under the taillight to soak up the leak, and it was still dry, it can´t be coming form the taillight.
It has to be coming from somewhere in the rear wheelwell? Could it be a leak from the gasket around the fuel filler? I´m not familiar with the anatomy of the E39 body shell, would a leak from the fuel filler area be able to make it´s way to the trunk?

[DoriDori]

Get in the trunk with a flashlight and have some one spray it down with a hose. Make sure all the channels around the trunk weather strip are clean of debris. The PO of my car parked under a tree in Savannah; it took my 45 min to clean out all the dead leaves and acorns.

[XAlt]

Get in the trunk with a flashlight and have some one spray it down with a hose. Make sure all the channels around the trunk weather strip are clean of debris. The PO of my car parked under a tree in Savannah; it took my 45 min to clean out all the dead leaves and acorns.

The outside of the E39 trunk area is stupid easy to get dirty, and I'm also parked under a tree.

[mcbanan]

I've been investigating this more, every time it rains i try to do something to help me narrow it down.

I bought a brand new taillight with new gasket and everytjing, but that did not help so i returned it.

I've been trying with some more paper lately, and it seems like it gets wet behind the pillar in the picture. The paper below the taillight is dry, and so is the paper towards the wheelwell. This is when the car is parked relativly flat, not driven.
Could it still be seeping up from below, or does it have to come from the top? I was thinking maybe a weld split behind the pillar there, but it seems a bit unlikely that a lot of water could be seeping upwards when the car is parked.

IMG_0591.jpg

[destahd]

I've been investigating this more, every time it rains i try to do something to help me narrow it down.

I bought a brand new taillight with new gasket and everytjing, but that did not help so i returned it.

I've been trying with some more paper lately, and it seems like it gets wet behind the pillar in the picture. The paper below the taillight is dry, and so is the paper towards the wheelwell. This is when the car is parked relativly flat, not driven.
Could it still be seeping up from below, or does it have to come from the top? I was thinking maybe a weld split behind the pillar there, but it seems a bit unlikely that a lot of water could be seeping upwards when the car is parked.

IMG_0591.jpg

Hi there, I know it's awhile later... did you ever find the source of that leak? I have the same exact one. I have replaced all gaskets and seals I can think of and cannot find the source for mine...

[mcbanan]

Hi! Well not really.. Earlier this year i moved to a new apartment with indoor parking, so it doesn't affect me as much anymore.

I did buy a new seal for the trunk though, but it didn't help. Next time I power washed it, it was still wet.

Just the other day I noticed something that might be relevant. Right where the body meets the bumper, on the middle rear of the car, there are two holes in the body facing down to the bumper. I imagine if you powerwash the car, some water will spray up and inside the car. Same thing if you park it facing downwards on a slope, water could run into the holes. I can try to take some pictures later, kind of hard to explain in a foreign language

[destahd]

Hi! Well not really.. Earlier this year i moved to a new apartment with indoor parking, so it doesn't affect me as much anymore.

I did buy a new seal for the trunk though, but it didn't help. Next time I power washed it, it was still wet.

Just the other day I noticed something that might be relevant. Right where the body meets the bumper, on the middle rear of the car, there are two holes in the body facing down to the bumper. I imagine if you powerwash the car, some water will spray up and inside the car. Same thing if you park it facing downwards on a slope, water could run into the holes. I can try to take some pictures later, kind of hard to explain in a foreign language

Hey, no worries at all and thank you so much for taking the time to reply!

In my case, I get water in the same exact spot, but it happens when it rains... I have the car parked on level-ish grass, and after it rains I find water in that spot. I too, have replaced the rubber boot seal, I don't think that's the problem at all. Tail light gaskets replaced too, but I don't think they were the issue (not least because my leak remains...) I'll be going into the boot with a torch this weekend and having someone outside with a hose spray different places till I find it. Will report in too.

[mcbanan]

IMG_0285.jpg
Here are the two holes I mentioned. Facing downwards. I'm sure anyone who's ever removed their bumper have noticed them. They could be the cause of a leak if the car is on a hill facing downwards, or power-washed. I'll be intereseted in hearing what you discover, destahd