Sills - What's inside yours...???

[Sonic ZS]

Originally Posted by Arctic

What purpose does this sectional foam have

1

Hi Arctic, as far as I know, the foam diaphragms are there to stop noise being transmitted from the sills up into the B-pillar, right next to the driver's & passenger's ears.

With the massively complicated & interconnected design of any modern bodyshell, vibration, noise and rumble from the front & rear subframes will eventually find it's way through to the effectively tubular sills, which can then act like a tunnel to move the noise along. Being connected directly to the base of the B-pillar means this unwanted sound would end up travelling upwards, next to the front seats, at head level.

On 75's, there's another sealed diaphragm across the base of the B-pillar.

In my humble opinion, the sill diaphragms do not directly cause rust - infact the rust in the rear of the sill always seems to have stopped just before it meets the foam. If they were made of open-cell, they'd hold moisture, but it seems the opposite is true - they are actually stuck so well to the surrounding metalwork that no damp can get close !!

However, they do stop any chance of air movement (exactly what I believe they were designed to do), and as such, might limit any moisture removal from evaporation within the sill. However, if this was the main cause of the rust in our sills, the centre sections would rot out badly as this area is sealed on all three sides !!! And as it is, 75's are generally very good in this area (.....except my S-reg....)

[Sonic ZS]

Found out yesterday (on S542AOX) that there's another, smaller foam diaphragm located up inside the rear wheel arch cavity. It's fitted below and roughly vertically in-line with the rear door catch.

I guess this again shows they don't cause rust, otherwise the normally susceptible arches would be rotting out at this point - something I've never seen

[Stephen Fussell]

Nice to hear and see that you are really cracking on with the car Paul. I can't wait to see the results.

[Sonic ZS]

Originally Posted by Stephen Fussell

Nice to hear and see that you are really cracking on with the car Paul. I can't wait to see the results.

Thanks Stephen, I haven't had the time to work on the car since the National at Yeovilton, but body repairs will now progress again. The N/S sill is now cut off along the full length and it's not a pretty sight inside. I've not seen a 75 this bad before, but I do love a challenge...

I doubt very much that your pristine example will ever require such surgery !!

[Stephen Fussell]

Originally Posted by Sonic ZS

Thanks Stephen, I haven't had the time to work on the car since the National at Yeovilton, but body repairs will now progress again. The N/S sill is now cut off along the full length and it's not a pretty sight inside. I've not seen a 75 this bad before, but I do love a challenge...

I doubt very much that your pristine example will ever require such surgery !!

I hope not

[Blink]

Just to say thanks to Paul (Sonic ZS) for all the pics. Excellent info - now we know how these things have been put together.

[smudge.g]

[QUOTE=I guess this again shows they don't cause rust, otherwise the normally susceptible arches would be rotting out at this point - something I've never seen [/QUOTE]

The rear wheel arches on my Tourer have started to bubble with some rust already in this area. Once the dam rain stops here, i will strip the paint and treat before it gets too bad! The front offside wing is already too far gone to save and is being replaced!