Water in rear footwell - Fixed!

[dom3.0]

I found water in my rear passenger footwell (UK spec 640d Gran Coupe)... And thought I'd share how I fixed it. I would definitely recommend doing this even if you think your car is dry - I planned to, but never got around to it, and I could have avoided a lot of hassle drying it out.

First of all, thanks to Russbmw for his excellent write up which you can find here https://www.6post.com/forums/showthread.php?t=1643842
Hopefully the below will help add to his guide!

Spotting the problem... The under carpet insulation on these cars is quite thick, so you might have a leak but not have noticed. One sign you have the leak is condensation around the Gran Coupe logo on the rear side glass. You can also lift your rear mats and remove the velcro disk (twist 90 degrees and lift), push down hard and if you hear any bubbling then it's time to get to work.

Fixing it... I'll open by saying I've never attempted any car repairs before in my life, but this took me about 40 minutes. The problem is going to be the cover over the yellow grommit that blanks out the steering column on LHD cars. There's a chance it could be the membrane on your rear door but this fix is so easy it's worth checking first. You need to remove the cover, clean out the gunk, add a bigger drain hole and seal the grommit. It's also worth clearing the drain holes as Russ describes in his guide, but I got my local garage to do that for me. Before doing this myself I took the car to my local BMW specialist, expecting him to know about it, but he just checked for leaks with a pressure washer - and wasn't interested in following instructions off this forum. Thankfully he didn't charge me so not all bad.

The cover in question is on the bulkhead here:


A closer look:


To remove it there are 4 Torx screws, one is out of sight on the top right of the cover, screwing in towards the wing. You can feel it easily enough with your fingers. One of my screws was very difficult to turn so I used a rachet wrench to turn the screwdriver handle. Once the screws are out a gentle wiggling will get the cover off.

Here's when it's removed:


And the reverse side... Notice the leaf mulch/gunk that has been held in place by the panel (even though its job is to keep this crap away from the grommit!)


Now a look at the yellow grommit. You can see lots of mulch at the bottom and a water tide mark showing it's been reaching the air vents and coming into the cabin.


Clean the mulch out:


Add silicone sealant to the grommit:


Drill a big hole in the bottom of the cover, just above the seal:


Glue something on the other side to keep the insulation away from the hole:


And then reattach. It was a little difficult to push the cover back on, but I found pushing it up and to the right side the trick.

Next up... Drying the carpet. My car had a lot of water back there, so I lifted the rear seat, pulled the carpet up and got to work with some towels. Shove a towel under the carpet and then squeeze the water out of the insulation, then swap towels and repeat.

The rear seat is held in place by a push-clip here:

I just gave a gentle tug and up it came.

Jamming a piece of wood under the carpet gave me space to work:


And the wife's hairdryer finished the job off:


A few days driving around with the floor vents on maximum heat and it's bone dry. No smell either so I got to it just in time. There have been some torrential downpours since I got it dry and no sign of any wetness - carpet is going back down later tonight.

Don't forget to also get the drains at the front cleared. Russbmw's write up (linked above) has instructions but I'm lazy so got the local garage on the case.

Hope that helps someone.

[Russbmw]

Nice work