How to cure chassis rust

[James Doulton]

Answer: Screw a sheet of aluminium over the whole underside of the cockpit, covering the rust holes so that the MOT tester doesn't notice. Unfortunately, I wanted to fit my new seats, so I removed the panel only to find this...

and this ...

That'll be why it was sold without an MOT last year by the guy who had owned it for many years. Then some scoundrel got it MOT'ed a few weeks later and then sold it for over twice what he had paid for it.

[1midz0wwbl268]

That is why fitting ally sheets to the underside is not a good idea,   it can come as a big shock when you remove it, if you have as many of us have done. rebuild your  car from the chassis up and you know its sound, then i can understand why you would wish to protect it, but surely, if you use a good quality paint and an anti rust primer  your chassis shouldnt rust like that has,  sorry James but  its going to have to be a body off  job and whole new sections welded in, if your going to do a proper job of it,  i would also look at the whole chassis whilst you have it off ,replace anything thats been weakerned  by corrosion.   which car is it ? Hope its not your leggy.   

[James Doulton]

It's the Legerra.

I am sure that a cheating scoundrel deliberately fixed the panel to hide the rust so that he could get it MOT'ed and sell it on at a profit. When I got the car home and jacked it up to change the wheels, I noticed the panel and wondered why it was there. It didn't occur to me that it would be such a cheating bodge - I thought MOT testers were wise to such things. I had assumed that the MOT meant that the car was structurally sound. It had only done 250 miles since the MOT when I picked it up, yet the chassis was rotten and one of the front dampers was leaking quite badly. Might have been a dodgy MOT station too.

[1midz0wwbl268]

Oh James, i,m so sorry for you,  it was most likily a dodgy MOT station, i would have thought any legit tester  would have issued a refusal to test as they could not acess the chassis to test for corrosion ? you should report this to the relivent authorities  ,and try to get the seller bared from ebay if possible.

As i see it your only option now  is to have the corrosion cut out and new metal welded in you might be able to pach some of it in situ, but to be honest  to be able to remove all the weakerned area, the body needs to come off.,  can you weld? if so then for your own safety you need to get it done I know its not what you would want to hear , i just wish it was better news 

[Dave Adams]

as an MOT tester you can only test what you can see, your not allowed to remove things to check behind....

[Paul Sheridan]

That's a bit of a blow mate, have you had a dig about over the rest of the chassis? does it appear to be in just that one place?

On my Phaeton, I had bad rust in a couple of places, but it seemed to be localised, and for no apparent reason!  I just cut out the rotted bits back to good metal and welded in a section.   

[Adrian Southgate]

Arse...

Those two are just seat braces and sort of non structural, get em boxed over with 2mm U section, drilled every 6 inches welded in the holes and welded at each end.

If you made the U section yourself then had it welded by a pro it would be just as sound as the original. It could then be replaced with box later. 

I'm tempted to fill the box sections with diesel and then drain them a day or two later, it would mean drilling a few holes but would help prevent further deterioration in the other sections. once drained they could be grommetted so inspection with a lamp would be possible later.

[James Doulton]

I think I need to get back under the car with a wire brush in my electric drill and/or with my angle grinder and see if I can find some bright metal under all of that rust. Then maybe I can formulate a plan to avoid taking the body off. I might as well do a complete survey of the car, just in case there are more horrors.

[1midz0wwbl268]

 Steve, in this case could james cut out the effected sections and replace  with box section tacking it as close to the top as it can be done with good penatrative welds along the sides and bottom, untill he can get at the crossmember , then  by removing some of the floor weld the top section later , would it be strong enough?   how much floor would have to be removed to weld it without burning anything? as long as a bucket of water and wet towel is close by  to dampen down nearby body work.

[James Doulton]

I think that once the seat is removed, then that part of the floor might be fairly flexible - it might be possible to prop the body off the rail by 10mm or so with wedges. That might be enough of a gap to prevent the glass fibre getting burnt.

[1midz0wwbl268]

It might be better to cut a secton of floor out and bond it back together , your only talking where it joins the main ladder , so a section about 3-4" square   but look at the rest of it first  and where its sound wire brush it  back and get some anti rust primer on it  to prevent it getting any worse

[Adrian Southgate]

Removing a section of the floor above each end has merit, would save a whole lot of messing about with chassis retaining bolts which is a right pain. Floor pan can be replaced in small sections if you feather the edges of the cut with acetone and apply a small strip of matting to add a little substance.

[1midz0wwbl268]

I would just screw an ally plate underneath the cut off area of floor and grease it up so that the fibreglass doesnt stick and build it up from  and  that do it one area at a time  , the more i think about it, removing a section of floor and cutting out the section , making a new bit complete with the attachment points for seat and roll bar etc then welding the new section in sounds the best way.