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      02-10-2015, 10:27 PM   #1
Varinn
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Water leak

What are all of the potential leak points on a z4 coupe? My '08 MC has a pool on the passenger side footwell that came back after I pulled the seat and vacuumed most of it out. I've replaced the vapour seal and all door panel clips, with the door closed and a hose to the outside I wasn't able to see any water drips anywhere but it's definitely finding a way in. If I corner hard or hit the brakes I get an inch or two of water on the passengers feet (usually the girlfriend's, she doesn't much enjoy it)

The only other place I can think of is the cowl drains, it looks like I have to pull the wiper arms and everything to get that bastard off?? I tried peering in with a flashlight but it seems like it goes into a cavernous maze underneath and I'm sure there is a deep dark corner hiding somewhere just begging to trap all the little leafy bits. Beyond wiper arms and what looks like a few screws, are there any tips to removing and replacing the cowl?

I can't see it coming from the AC as it's currently winter so I haven't been using the A/C at all. I had fogging and musty smell when I first bought the car in late summer so I checked it, didn't notice anything. It wasn't until winter rains started that the pool showed up and I realized it wasn't an A/C issue.

If anyone has any "while I'm in there" tips for the cowl re&re I'd like to hear them. It'll be tough to squeeze the job in this week but it's definitely got to be done soon.
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      02-11-2015, 05:36 AM   #2
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So I'm new to the E86 chassis; I've only had mine about two months. But last weekend it was warm so I had chance to dig around a bit and check out the design an engineering of the E86 chassis. I'm quite familiar with BMWs after 26+ years of owning them. Anyway, the cowl drain on the Coupe is HUGE. If you look on the passenger-side under the hood near the firewall you'll see a big, flat oval rubber tube, with a big rubber flap at the end. That's the cowl drain. Check to see if the flap is opening correctly, and that it isn't full of debris, or a mouse hasn't built a nest in the drain. I'd suggest finding a shop and asking them to shoot some compressed air back up the drain tube in case it is clogged.

Also, if you can find a shop with a smoke test machine (they use them to find vacuum leaks) the shop can use the smoke machine to find leaks in the cowling/windshield seal. I doubt the water is coming through the door since the door drains are below the door sill, but you should check them for clogging as well.

Good luck.
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      02-11-2015, 03:35 PM   #3
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If you use the defrosters the A/C will run, even if you have the heat on.
Passenger side floor is a common place to puddle if the drain tube falls off.

You're sure its water and not coolant from the heater core?
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      02-11-2015, 05:22 PM   #4
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Definitely not coolant, does not have the smell or texture of the mix, plus my levels have not dropped and the amount in the cabin is significant enough that I could not possibly continue driving the car if I had lost that much.

Where does the drain tube connect? It was still visible above the trans last time I checked and I did have water dripping from it. This was late summer last year when I first noticed the water smell, it appeared to be working correctly.
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      02-11-2015, 07:39 PM   #5
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Quote:
Originally Posted by Varinn View Post
Where does the drain tube connect? It was still visible above the trans last time I checked and I did have water dripping from it. This was late summer last year when I first noticed the water smell, it appeared to be working correctly.
There's a big grommet on the top of it that pushes through the floorboard at the top of the tunnel.
Above that, I have no idea.
The diagrams on realOEM are a little ambiguous on how it all connects together.
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      02-12-2015, 09:51 PM   #6
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I looked into the cowl last night without any luck, pulled it off and there wasn't a spot of dirt or leaves in any of the drains, poured a few buckets through on both sides and found it drained as quick as could be. Tried pouring water over the firewall grommet without luck, and over the passenger door.

I pulled the speaker grill panel, the panel under the glove box, and the door sill trim during all of this. I saw no traces of water coming in anywhere. The cabin air filter was bone dry, and I noticed that the water deflector under the cowl trim was seeming to work well as the vents just past it stayed bone dry despite the water we were pouring into the cowl.

At this point I'm trying to arrange to set up over a weekend in my friend's autoshop and I'll pull both seats,the center console, and all of the carpets to see if I can find anything. The pool is seemingly getting larger, and I've got no idea where it's coming from!

Does anyone have a walkthrough on pulling out the center console so I can get the carpet out? I'm sure I could work my way through it, but it seems easier to have a guide.
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      02-20-2015, 09:07 PM   #7
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Got busy with it tonight after work. Got the seats and most of the front lower trim pieces out, but ran out of light in a right hurry. Removing the driver seat from a z4mc is a real cunt of a job until you get the angle juuuust right then it sort of glides out with ease.

I've found a guide that highlights all the hidden bolts on the center console and how to pull the carpets so I should have them in the garage by mid day tomorrow to start drying out. With the carpets and most of the trim removed it should be a breeze to spot the water trail with a hose to the exterior.

I've stocked up on all sorts of clips/gaskets for re-assembly, just have to hope it doesn't end up being something stupid like my windshield or roof seal. So long as it's a simple piece I should have no problems getting it resolved once I find the culprit.
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      02-21-2015, 08:51 AM   #8
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Maybe you really have a roadsta?
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      02-21-2015, 09:21 AM   #9
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I will be interested to hear the outcome. Really sucks to have to deal with a leak when you don't even have a sunroof... I am thinking the A/C drain will be the issue.
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      02-21-2015, 10:53 AM   #10
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I'm having the same problem on the driver side and haven't been able to figure it out either
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      02-21-2015, 09:42 PM   #11
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Some progress. Removing the carpet was quite the task, luckily a fellow mechanic buddy of mine dropped by and we found a way. I wasn't keen on cutting it, but the alternative was removing the dash and I don't have the space or time for that sort of work.




I am lucky enough to have an upholstery cleaning vac, so we removed most of the water then used my buddies heater fan to dry out the interior. The carpets are currently sitting in a bathtub with the fan aimed at them and drying quite quickly.


When spraying in the corner near where the door/windshield are we get water. We found that it comes in when spraying either directly down the small triangular opening at the top front corner of the door, or when we spray the bottom of the glass it runs down into the hood's hinge pocket/cowl. The cowl itself is clear, though I feel that the little plastic clips on the cowl cover are somewhat suspect. I will replace them tomorrow.


Speaker labeled here to give a reference for where the camera is. It looks to me that the pocket where the water is coming out of is roughly in line with the hinge plate for the door.


We removed and checked the electrical connection and applied a thin coating of sealant to the grommet. This won't be the source, it's too low to be the cause of the leak. Circled in red are the two areas where we were sort of focusing the water spray, BOTH seem to cause the leak as far as we can tell.


In this picture you can see somewhat where I am talking about spraying water. The hood pocket leads to the underside of the cowl, as well as on the glass. Any water getting under the cowl cover SHOULD run down the drain, but I'm wondering if maybe the gaskets on the clips are worn out and it's getting into the inner shell through one. In the dark upper left hand corner you can see where we were putting water down onto the door hinge, but it's a shit photo.
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      02-22-2015, 10:25 PM   #12
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More progress!

No idea where the hell its coming from!

Its not the windscreen, we are able to replicate the leak by spraying below it and the window seal doesnt even get wet. The door hinge doesnt seem to be it either, rather it comes through near it but trickling over it doesnt cause it either. Somewhere behind it maybe... A spot weld on a bracket possibly?

The stud that is barely visible right at the rear corner of the hood in my last picture is roughly the area we suspect. In all honesty we are thinking that the only way to find it is to pull the fender and check the brackets behind. I'm unsure if I have the means to do that at my home garage, running out of space as it is.
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      02-23-2015, 04:06 PM   #13
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This is how my roadster was leaking. Water was running between the fender and the door at the base of the A pillar. It was hitting the plastic piece that you have circled in blue. That piece was diverting the water to the small channel that runs down the gasket seal (see my new blue line showing the water direction). The water runs down the seal until it gets to the door sill area parallel to the ground. From there it was flowing into the floorboard as a steady trickle (see my blue line), depending on how hard it was raining. I came to the realization that "maybe" the round hole in the gasket, circled in red, was supposed to allow the water to run out under the gasket. If that was their engineering genius, the hole was way too small. I took an X-acto knife and turned the small circle into a rectangle, about 3/4" long by 3/8" wide............ problem solved, no more water running into the floorboard (I added the rectangle in red, for reference, below the existing circle in the photo...... the new rectangle I cut however was in the exact spot as the circle, I just enlarged it). This leak drove me crazy, and the only way I solved it was by being stuck in rush hour traffic at a standstill during a torrential downpour. I began studying the problem, went home and later recreated it with a water hose. It's hard to believe the enlarged circle to a rectangle stopped it, but it did.
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      02-24-2015, 01:42 PM   #14
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Sadly mine is not looking to be that simple, it is definitely coming from up high above the speaker through the little bracket seen in the picture. I can't tell quite what is on the other side of that hole though, it seems to line up with the hinge plate, but the leak comes through when the water isn't really in the area of that door hinge. Somewhere further forward is a strong possibility. I'm leaning towards a poorly sealed seam. I should have the fender off this week when I get the car to a buddies garage and have the space to store more parts on removal.
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      02-24-2015, 03:27 PM   #15
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May be worth a try anyway before taking the fender off.
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      02-24-2015, 04:42 PM   #16
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No reason to do any changes to the door seal, it's definitely not coming from it. There is a single obvious source that is well above and away from the door seal. With the speaker removed from the opening and peering inside it's obvious that the water is not coming from the electrical grommet either, as it is bone dry and far lower than the source.
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      03-01-2015, 10:33 PM   #17
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Checked further into it this weekend, got more of the dash removed and we've guaranteed that its coming from right up at the corner of the windscreen/cowl by following the water trail.

Fender off, not too bad actually. About 30 minutes while taking care not to damage any of the paint.


There are three likely sources, as far as we can tell. We tried soapy water outside with an airgun inside but nothing showed a leak because of the cavity the leak is in. This stud, while unlikely, seemed to be a probable candidate. We were able to consistently get water when trickling over this spot.

We applied a hefty dose of a thin glass sealant that flows well into the edges around that stud, the corner of the windshield gasket, and into a seam found inside the frame rail under the fender (through the biggest hole seen at the top rail). We then covered them in a silver brush on body sealant like the factory uses. There are lots of obvious external drain passages designed into the body structure, so putting sealer was done ONLY where factory sealant looked thin or broken.


Top edge of the window seal, no water visible from above the dash when focusing the water spray on the corner of the glass. Can't see the bottom edge when spraying.


Looking through the HVAC vent, the overexposed metal plate is mounted to the cavity the water is coming through. We can follow the water up to a hole on the bottom of it, but thats as far as we can go. Removing the dash doesnt look like it would help us see into it, so we are avoiding that extra work at the moment.






Light rain here at the moment, still leaking.

Last edited by Varinn; 03-02-2015 at 05:16 PM..
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      03-01-2015, 10:54 PM   #18
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bloody hell.. mate sorry your going through this buddy.
hope you can track it down..
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      03-02-2015, 01:11 AM   #19
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what a nightmare!!

luckily this isn't a common issue! wow.
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      03-02-2015, 09:50 AM   #20
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I wouldn't want to do this much work to my car if it added 100 hp.
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      03-02-2015, 10:35 AM   #21
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Haha, I've done worse jobs in my driveway in the past! The way I see it is it couldd be worse, but after sinking 2 weekends into it with another mechanic buddy of mine we're not really any closer to finding it. I'm limited to working on it for no more than an hour or two after work through the weekdays because it gets dark quickly.

I'm thinking to put a seat in it tonight, I'll drive it to work tomorrow morning and drop it off at my buddies BMW shop in the afternoon. Might turn out to be a shite bill to pay as he's thinking to pull the dashboard as a next step in just finding it, let alone whatever the fix is. Previous owner had it a dealership to try and solve a water problem, they put tape over the holes on the door panel clips and called it fixed. I can only assume the tech didnt have eyes, or it would have been clear it was somewhere else.

Part of me thinks it's the windshield gasket, hopefully a smoke test can find it. Not sure if it will have enough pressure to push the smoke through though with that cavity being only spot welded around the edges. If I can't find the source, well, I'm hoping to get a house with a garage to fit all three vehicles soon...

Last edited by Varinn; 03-02-2015 at 10:42 AM..
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      03-02-2015, 12:41 PM   #22
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Wow, really sorry your going through all this. Looks just awful.
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