Driver's door seal leak

[stephend]

To celebrate the new year, I'm finally tackling the rainwater leak(s) on my 740. Just the job for freezing December/January days! I originally planned to tackle this in the summer, but a sodden rear footwell has forced it up the agenda.

One place that water is definitely getting in is from the driver's door seal into the driver's footwell. With the trim out, I can see drips emerging from the seal just behind the base of the A-pillar, in the first inch that's horizontal after the radius'd corner, and running down the inner sill into the footwell. The question is, from where is the water reaching this point...?

With the seal removed, I've been looking at the flange that it clips to. I see that in places, the flange consists of three plies, the middle ply (presumably) being part of some internal structure in the sill or A-pillar. And in places, there are gaps, approx 1 cm long and 1 mm wide, between regions of the middle ply.

I'm hypothesizing (!) that water is coming out of one of these, and running down the inside of the U-channel clip part of the seal down to the point of egress. My first question: are these gaps supposed to be filled with sealant? There's some black silicone sealant which I put there on a previous attempt to fix the leak, but there's also some grey sealant (stilll gooey) in places. I don't know if that's factory original or not.

The other question, of course, is: where's the water getting in in the first place? I can rule out sunroof and roof bars, because mine has neither. I've got some rust around the w/screen frame, which I haven't investigated the severity of yet. (I really don't want to be tackling that mid-winter!) But I also have the impression that the front of the rain gutters drain into some kind of duct in the A-pillar, the opening being a couple of inches below the top corner of the w/screen. Is this right?

I'd be really grateful for advice on this: I haven't spotted any mention of these points on relevant threads.

Background: the driver's footwell has been getting water in for years. Occasionally, the front passenger footwell does as well, but I've never found any wet in the rear footwells until a couple of weeks ago.

I've previously investigated the A-pillar vents, and I'm pretty sure they aren't letting water in. I've also run several buckets of water through the scuttle. Outflow through the chassis legs is copious, so there's no blockage, and no water came into the footwells while I was doing this. So I'm inclined to rule out the heater inlet seal. It's definitely rainwater, not coolant or screenwash, and the heater valve is bone dry. As mentioned, there's no sunroof or roof rails. I've currently got the carpets, underlay etc out, and the front seats out as well, so I'm committed!

Thanks for reading!
Steve

[Chooch84]

If the accelerator pedal is no different than the one in the 940, you'll find that the nut inserts used to mount the pedals live on the firewall/dash panel, just to the RH side of the brake booster, the "nut-serts" live quite close to the RH inner wheel arch panel which has a seem running near it.

Although the pedal mounting plate looks to have some sort of seal on the back of it. It's a bit of poor design due to the production process by the looks of it. Ideally, the nut and bolt should be sealed over in the engine compartment, as opposed to allowing the water to ingress then expecting the seal on the pedal to stop water coming in.

[Chooch84]

You could try some soapy water and some air to try to identify the point of entry, or go a bit "CSI" with some UV DYE and a UV Torch.

[stephend]

Chooch84, thanks for both suggestions.

I had a very quick look at the pedal fixings from inside, and they look pristine. But I'll follow that up properly when the car's outside again.

I love the UV dye idea: properly forensic!

[stephend]

Update: I've found one leak. I was poking about in the n/s/f footwell, and found a rusty-looking bit. So I poked a bit harder - and now it's a hole through to the rear part of the wheel-arch. It's located where the footwell pressing meets the back of the wheel-arch pressing, on the outboard side next to the A-pillar. Time for some welding...

Given its location, it can't be letting rainwater in while parked, only when driving in the wet. I'm not 100% sure if rain's getting into the n/s while parked (which would imply another leak), so that's still to check.

I've taken the glovebox out for better access, and I can now see the heater inlet from underneath. I'll chuck some more water into the scuttle and see if any appears inside.

[Chooch84]

If possible could you take some pictures? Would be interesting to see and share your experience.

Manufacturers have known wet areas and seal adequately, if any panels, under-trays, heat shields are modified, removed and not seated correctly, damaged etc... this can obviously lead to area's of the car getting subjected to water which normally shouldn't.

I caused a water leak in my old BMW 1 series when I removed the plastic scuttle panel... it started to take out all of the electrics of the car. I thought I put it back correctly, it's only when I noticed the footwell was soaked I figured out what I did, by that time it was too late...

[stephend]

Inside (before I made a hole in it!):

VOC_1.jpg

From wheelarch:

VOC_2.jpg

[Chooch84]

Does the 740 have Wheel Arch liners? I know my 940 does.

[stephend]

It seems to have some sort of liner round the edge of the wheelarch, to protect the flange. But the main part, no. Spray from the wheel hits the back of the footwell direct. Copiously undersealed, of course, but it's a 30+ year old car...

[stephend]

Another discovery, this time in the driver's footwell: a pinhole leak in the seam of a plate welded on for a previous MoT.

At some point, I'd really like to cut out the MoT patches, and fix the floorpan properly, otherwise there's a danger of chasing rust round in circles, one patch at a time.

Not that I'm claiming to be a better welder than the MoT man - but he's trying to keep down the cost to the customer, whereas I can take my time.