Mk1 Eunos sill bubbles - sign of worse inside.

[Mighty Flex]

Car is a 1990 Eunos imported in 2000 i have looked at. Arches are good and look original - the sills look tidy and possibly original (no mot history mentions corrosion at any point) apart from this at the back on the passenger side:



The rest of the car is good, low miles and healthy, bar a few scrapes that could be sorted. Underneath looks good too, but I fear this is a sign at least that section cutting out, and hoping the inner sill is still good? Or could it just be the surface?

Thanks for any answers.

[Mighty Flex]

thanks - I have a usb borocope, but didn't have it with me unfortunately. looking at similar ones that have been repaired: it looks like the inner sill will probably just need cleaning up and rust proofing followed by a sill only repair panel on the outside (need not extend up the arches like some). I guess this done properly is around £200+. if worse underneath it could be more...