box section - where can the water/rust get to and ...

[Chief]

Hi,
Ages ago (prob 2 years or so now) I posted about how our new chassis', new box section had become full of water, how we'd drained it out, dried it as well as possible, and then used some waxoyl as best as we could inside it (it still looks like its just some surface rust).

However being a worrier for rust (even our new indicator stalk has started rusting through so I'm not a worrier for nothing ) I've always wondered where the water could get to from the box section, are there any other panels it could have leaked into (such as the sills ) or does it retain its water in the box until the rust eats through the floor of the box section (which I take it is one of the rear floor panels?).
I know the rust hasnt managed to get through to the panels under the carpets at the back of the car, but is it possible for the sills to be reached etc.

The reason I'm asking is a while ago a friend of mine (whose hobby is car repairs) on my asking him about cleaning out the rust said it was perfectly acceptable to chop the top of the box section, get in with a good wire brush, clean it and paint it all up, and then weld the top back on the box section again, and I was wondering if the rust could have reached any other areas or if we really could just do that, clean it all up and not be worried about the large area of rust (though at least its now dry).

The underneath of the car is (according to our local garage) still in good condition so I'm hoping that means it can't have spread.

Also has anyone any idea of how expensive it would be to get an (expensive) garage to cut the top off the box section and weld it back on (hopefully they'd let us do the actual rust removal to save money).

Oh and also, does anyone know what the area under the back seat (the sloped panel leading towards the box section) is coated in. It was a sort of rubbery stuff, that was all bubbly on top and painted green (great description I know) I just wondered whether it was some sort of sound proofing paint, or heat resistant or something since it was a good 1-2mm thick. When the water had come in previously it had run behind this stuff anyway and to reach the rust i had to scrape it all off, I was just planning on priming and painting the area but I wondered if this was some special stuff it was wisest to put on or not.

Thanks,

Chief

[Alec]

Hello Chief,

probably the best solution is to have drain holes in any box section and that with regular waxoyling should be adequate. The problem with totally sealed sections is condensation so a drain is required in my view.

The compound you describe is sound damping and you can buy stick on panels that will do the same job, once you have finished painting.

Alec

[Willie]

Very true, the less ventilation and drainage there is in a box section the sooner rust will form. The Minor does not have enough drain holes and they are not in the ideal places either. I would advise you to check, in particular the bottom section of the rear quarter panel(under the rear side windows). it is easy to remove the trim panel and you can then inject Waxoyl or whatever you prefer down there. This is a notorious rust trap. You can also inject waxoyl, good pressure needed, into the ends of the box sections which extend over the rear axle and which are found in the boot on either side.