The carpet is soaking behind the driver seat and I don't know why or where to start looking

 

Coupe or convertible ?

What year ?

 

It's a 2010 coupe

 

With an earlier car, I would suggest looking at the "seal" where the driver's side window meets the rear "quarter" window to see if there's a gap through which rain might be seeping. As we know, there's been a lot of rain the UK over the past couple of months.

But - not sure if the design of yours would be the same as the earlier model X100s.

 

Welcome to the forum Helen,
I've moved your post to correct section.
Please post an intro in the new members section when you can.

 

If it was leaking through the window or seal, wouldn't the inside of the door be wet too?

 

Helen,

If you can't find the source, this company is in London and should be able to help:
https://cars.newagain.co.uk/car-water-leak.asp

You can also Google "smoke test for car water leak" for more advice.

Good luck, and please keep us updated.

Stuart

 

Not if it was running down behind the interior panel.
Take out the back seat and see if there is any wetness under it.

 

Same as me, 2007 coupe... completely soaked behind drivers seat, about 1/8" puddle of water and rusty seat belt mounts. After removing carpet I couldn't find the source but I ended up sealing everything I could, every little dam spot where I thought water could come through. But none of that will matter if its somehow coming from above and draining down.

 

So is this a coupe only problem or has anyone with a convert had the same issue.

 

My convertible has had some wetness in the trunk area. I have not tracked it down, but I have not really tried either. Plus my car has been hit in the rear which could potentially be the cause, though the repair job was excellent.

 

In my BMW, there were drain ports in various locations that would clog with leaves or pine-needles or other obstruction, and that would cause puddles in some areas until you unplugged the correct drain point. Perhaps that is the problem with the coupes.

 

Sometimes my drivers side seat belt is moist after a hard rain. So I know I have a leak somewhere also.

 

I concur with the Smoke Test. Most auto shops can do this, and the equipment is not expensive which means the test in cheap. Cost maybe $50 tops to find a leak.

 

COuld this not be related to the HVAC drain duckbill being clogged? In the UK the drivers seat is on the right.