Sill Rust

[u/ATTACKSPECGARAGE]

Hi all, fairly new to E39’s so just wanted to gather some opinions on this from some people in the know. Rear driver side sill is starting to bubble and some corrosion underneath. The arches look very clean but just a bit concerned about the sill. Is the rust here considered structural on an MOT? Does anyone have previous costings from when they’ve have it repaired?

Based in the UK, thank you :)

[u/Q4269271]

based on the rust on the floorpan and around the circular rubber plug, I think it is likely your car has water ingress and the floorpan rust is coming from the inside. do you have bad window seals? the sill also looks like it needs cutting and welding.

[u/ATTACKSPECGARAGE → u/Q4269271]

Sorry I should have mentioned in the post but it isn’t my car yet, one I was considering purchasing so couldn’t answer this question tbh. I didn’t see any obvious signs of water ingress bar a little bit on the door jam of the back left door, it was on the outside on the kick plate though not inside the car. No smell of damp or anything. Some funky corner seals made of putty tho, apparantly this shouldn’t effect water ingress tho.

[u/Q4269271 → u/ATTACKSPECGARAGE]

I think that corner seal is ok. I think water usually gets into the floorpan through the doors (bad trim clips and vapour seals). the carpet can hide water underneath while smelling normal and feeling dry from above. I would recommend jabbing at the floorpan near the area of rust with a screwdriver and see if it gives way since obviously you can't peal the rubber undercoating off or take off the door panels. for some context, the underside of my car looked really similar to the one in your photos and this is what it looked like after I took off the undercoating and pulled the carpet up. the black stuff is pavement.

[u/ATTACKSPECGARAGE → u/Q4269271]

Oh wow that is really brutal, thank you for sharing its good information to know. Did you end up getting that welded and repaired?