Sorting these common MOT fails.
Rotten rear sill edges and inner wheelarches are common MOT failures. Rob Marshall explains how to execute a quality DIY repair.
It’s no surprise that the inner rear wheelarch has become such a common rust spot on vehicles. Even if plastic liners are fitted to the wheelarches, moisture can be held against the metal. The point at which several panels are welded together creates a weak spot, which is bombarded with stones, grit, moisture, mud and salt that are thrown up by the rear wheels. As so few motorists clear regularly the damp mud that accumulates in the arch, the damage is hidden from view.
Unfortunately, this damage tends not to be superficial. Once established, corrosion can spread quickly into the inner sill, until the decay is spotted, often too late, at MOT time. By then, an extensive and expensive repair is likely to be required.
As welded repairs have become ever more specialised and regulated, many
garages do not have the necessary equipment and expertise to carry out the task for you. In any case, the labour rate alone may eclipse the worth of a lowvalue, but otherwise immaculate, older car. However, it can be cost effective to make your own repairs by renting a welding machine and following the advice from our welding feature in the August 2017 issue.
Ignoring the appalling paintwork and botched repair, corrosion spread from the wheelarch on this Nissan into the rear end of the sill. The resulting MOT failure caused this example to be scrapped.