Corrosion develops in the hollow box and double skinned sections of the lower body, eventually spreading throughout the lower bodyshell.
The expedient method of repair, used mostly to satisfy the MOT inspection, is to weld patches of metal sheet over the rusted areas. Far from solving the problem, it only makes matters worse by sealing in the damp.
The long term method of repair is to cut out the rotten sections and replace them with replica strength panels, thus eliminating the problem of structural rust.
This shows a typical chassis that has been repaired. The severe rust areas are shown in orange and are related to the hollow frame. Bottom flange laminates in the centre cross member (A1) open up and damp gets into the vertical laminate causing structural weakness.
This shows (in blue) where MOT patches and cover panels are used to disguise the condition of the underbody
Reconstruction costs of a rusted out Minor make the cost of annual MOT welding seem insignificant. On average the parts and labour come to about £2850 and an 80% lower bodyshell rebuild around £4250.
The good news is that in all but the most extreme cases this work can be staged over a few years to suit your cash-flow and targeted at replacing the panels likely to fail the MOT on basic safety.
Usually a few hundred pounds spent logically will halt the decline. This work will be covered by our 2 year guarantee. When we replace a complete centre to the car, from wheel arch to wheel arch, we give a 4 year guarantee provided you follow our simple annual maintenance programme. The cost of this complete centre replacement can cost as little as £2,750 + VAT