Really??
- Joined
- Sep 28, 2015
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- M44
I thought my question relevant to this thread because as far as I can tell, the drain tube exits the bottom of the B post and terminates inside the sill. As I am replacing the outer sills this winter with new ones already bought, I was interested to know if anyone had thought about the water getting in there from the drain tubes and causing rot? Sorry if this caused offence, it was a genuine question that didn't really justify sarcasm unless I am missing something.
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I am also interested I have recently changed some sills and I found LOTS of debris and small leaves behind the rear wheel arches that I believe come from the little drain that is on the top corners of the frame where the boot lid sits right behind where the hinges of the boot lid meet the body, otherwise I can't find any other explanation but maybe you are right - It would be good if someone can post some pics
Check @FRANKIE video on YouTube. In it he pours water into the drain and you can see where it comes out.
Not sure where else BMW could have put the drain exit to be honest.
On an E85 Z4 the drain is outside of the sill cavity, in front of the arch liner, the Z4 doesn't appear to suffer the same amount of debris behind the liner as the Z3 does.
Tony.
Not sure where else BMW could have put the drain exit to be honest.
On an E85 Z4 the drain is outside of the sill cavity, in front of the arch liner, the Z4 doesn't appear to suffer the same amount of debris behind the liner as the Z3 does.
Tony.
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And that's where I expected to find the end of the drain tube as with the Z4 and not terminating inside the sill. When I eventually take my sills off, I will look at whether its possible to extend the drain, through the bottom of the new outer sills to stop water collecting inside. However, I didn't want to reinvent the wheel if somebody else has already done this but to date, with all the sill replacement articles I have read, none seem to have looked at this.
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I will do as so far, nobody seems to have been looking at this. The other day I poured about 300 ml of water down each tube and it all came out along the outer sills where they meet the floor so little wonder the inner sills are getting so rusty and the outers, rotten. I suppose in fairness to BMW, they didn't really expect these cars to still be going strong after 20 years. And, it could be worse, it could be an MX5. Now they really know how to rot.
As @t-tony said. when I was replacing my roof, I noticed the drain holes behind the posts that are just behind the seats on the inside near where the last bolts are that hold the bow on the left and right sides of the car. Those holes are about twice the size of an ice cube. On my car, there was a small piece of rubber attached to the top edge of this cube. This cube is 5 sided as there is no top to it. On the bottom or 'floor' of this cube, slightly forward of the center is the drain hole. The holes are almost impossible to see without a mirror. I was able to see them easily as I had removed the black bow that goes from one side of the car to the other and is bolted on to the frame of the car to hold the very end of the top in place. This bow sandwiches a ribbon of waterproof tape or caulk between the top and the body of the car. The water draining off the roof must follow the seam between the end of the top and the car body to either side and is directed into these cubes with the drain holes. You probably already know all this. What I think has happened, on your car, is that perhaps these tubes got blocked and had a constant supply of water that had nowhere to go since the blockage prevented the tubes from draining. After time, they might have rusted out and started draining into your sills allowing the condition you are now observing. My used car had always been garaged and rarely driven in the rain. This might be why the drain holes never got blocked with dirt and still drained properly...................................Frankie
P.S. This is almost the same that happens to sun roofs. Behind the piece of glass are two drain holes for rain water. Any car I've owned with a sun roof had drain problems as these holes ALWAYS got blocked. In this case the backed up water then drained into the cabin, usually on top of your head. I used to have to remove the glass sunroof and open up wire hangers and ream out these drain holes if air pressure didn't work first. What a pain in the a$$.........................Frankie
@FRANKIE thanks for this insight. I very recently had a full restoration of my Z3 and if I had known this at the time, I would have asked the bodywork company to sort this out. I'm assuming there is a solution? @t-tony @GeoffZ
It would be great to have photos and step-by-step guide in the form of a "How to" or a YouTube vid on how to stop this from happening, please.
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Well no not really. I have no problem with the drain catch cube at the top and the drain tube in the bottom of that. On the inner face of the B post, there is a rubber bung about 80 x 25mm. If you remove this, you can see the tube and that it goes down to the top of the inner sill. My drains aren't blocked but, I was trying to figure out where the water actually went and how the soft top drained. Thats went I tested it with 300ml of water and saw that it came out of the sills at the join between the sill and the floor (outside underneath) as it is intended to. My issue is that the drain system introduces water from the soft top into the sills and causes the sills to rust, unseen, from the inside. So, my quest is to find a way of extending the existing tube so that it drains to the outside without dumping its contents into the sill box void. I won't know how I am going to do this until I remove the sills this Winter. I just wondered if anybody else had done this mod before. Having figured this out, I am not happy with it and want to come up with a solution to prolong the integrity of the structure that is out of sight.
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I understand what you are saying and it's a scary thought. In the video I took of pouring water down into this drain hole, it emptied from one point. I can't remember if I got down on the ground and actually SAW the point from where it emptied. I thought I did because I couldn't locate it by just looking under the car and I thought I actually got my face down there to look just above the point where the water was hitting the ground and seeing the exit hole. I thought I actually did this but as it was several years ago and I've since sold the car, I can't go back out there and look again.............I don't know what to tell you...................Frankie
One thing I do remember. When I poured water down these drain holes, it exited at exactly the same spot on each side of the car. I'll see if I can find the video..................Frankie
P.S. I got tired of trying to search for this on forum posts so I entered it into the Z3 Knowledge Base/
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Took me about a half hour to find it but here it is. Notice that it drains from the same relative location on each side of the car?
No offense caused, I was just surprised that bmw would drain things through the inner sill. If that's the case they're asking for trouble!
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Hi Frankie, yes the water in mine exited in vaguely the same place, onto the floor too, but I watched it coming out and it actually comes out through the gaps in the floor to sill join created by the flutes in the floor pressing. When I conducted this experiment, I expected to locate a rubber tube sticking out somewhere but no. I searched the internet high and low (found your video too
) but could not find any definitive answer except I have seen the tube in the B post and I know it goes through the top part of the inner sill box section. Wish now I had taken a photo but the interior is now back together. I suspect that the drain isn't obvious and is hidden behind the inner sill so doesn't get any attention when outer sills are replaced. So, to those about to do their sills, maybe have a look at this and report back on any findings before bolting on those shiny new sills. Otherwise, I will tell the story this autumn when I do mine. In the meantime, the following link shines a little more light on the subject though in my case, the water ingress was eventually traced to the plastic scuttle panel allowing water into the heater fan ducts.https://www.bimmerfest.com/forums/showthread.php?t=890640
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According to a garage mechanic friend of mine, this isn't unusual and sunroof drains on other cars cause similar problems. As a drainage method, it ok whilst the factory rust proofing works but when that eventually fails as it must, the rot begins. For my part, I just want to eliminate an archilles heal that could limit the life of the structure and won't be seen or known until its too late to save.
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You can see the catchment cube with the soft top down. Its the bit that has a rubber trim around its edge. If you put your finger in the catchment cube, you can feel the hole towards the front. Once you know where it is, you can put a piece of wire down it to clear any debris. When you do that, you will be able to hear the end of the wire knocking around at the bottom, in the sill void.
Be interesting to see where the coupe drains!