Bmw 4 series Coupe Water Leak

[SDerbyshire]

Yesterday i found a small lake in the read drivers side (uk car) footwell of my 2015 4 series coupe.
All other footwells and boot are dry, the floor level heating feeds are dry and dusty so i don’t think water is coming down those.

I have done a long road trip in rainy conditions last week.

I’ve read the thread on the convertible but as mine is a coupe, no sunroof, my problem does not seem to have the same cause?

Has anyone seen/fixed this issue on a coupe before?
Does the coupe have the underfloor drains that the convertible has?

Thanks in advance for any help!

Steve

[SDerbyshire]

I mopped out the lake yesterday and finished off this morning, decided to check the other footwells again.

All dray apart from a tiny bit of dampness aroung the pedals in the drivers footwell

I wonder if the water is getting in her, but running back and accumulating in the rear footwell?

[Aluminati]

Wait till you have to put a new amp in…

[MitchT]

The only suggestion I can offer is that maybe the rear side window on the affected side was slightly open and let water in. If they're anything like my E36 3 Series coupé they angle outwards and if one was only open slightly it might not be obvious. I don't know how you open them on the 4 Series but if they're electric and the controls are part of the cluster of buttons on the driver's armrest then maybe the button was knocked just enough to open it a little. Anyway, I'm watching with interest as I'm on the lookout for a 4 Series coupé.

[SDerbyshire]

MitchT said:

The only suggestion I can offer is that maybe the rear side window on the affected side was slightly open and let water in. If they're anything like my E36 3 Series coupé they angle outwards and if one was only open slightly it might not be obvious. I don't know how you open them on the 4 Series but if they're electric and the controls are part of the cluster of buttons on the driver's armrest then maybe the button was knocked just enough to open it a little. Anyway, I'm watching with interest as I'm on the lookout for a 4 Series coupé.

Thanks for the helpful suggestion Mitch, however the rear windows are not opening !

Steve

[dxg]

I had this problem in another make of car.

The waterproof membrane in the driver's door had come away at the bottom. Yet, somehow, it was the rear footwell where the lake formed...

The telltale was drips of water appearing on the underside of the door where the door card met the metal.

[SDerbyshire]

dxg said:

I had this problem in another make of car.

The waterproof membrane in the driver's door had come away at the bottom. Yet, somehow, it was the rear footwell where the lake formed...

The telltale was drips of water appearing on the underside of the door where the door card met the metal.

This seems to be a common problem on bmws…… so today i stripped off the door card and found the moisture/vapour barrier was indeed disconnected from the door for the back 10” or so.

Is this really enough of a problem to flood the rear of the car ?

Thanks for the replies so far.

Steve

[helix402]

It is a common problem. Butyl tape is the cure.