Sills

[Mk3 16v Anniversary]

Either my car is the only Mk3 with rust under the door seal rubbers or everybody else here has been extremely lucky!

[Justins145bhpMK1]

I had a quick look at mine this morning, yep the trim bubbles up when the metal in the trim corrodes, actual sill is solid though.

[Mk3 16v Anniversary]

The corrosion on mine is NOT under the "GTI" sill protector plate.  You need to look carefully under the rubber door seal to spot it.

[modulater]

I would guess that the paint has been chipped off by something being put in the car and that the seal has trapped water there which has caused the corrosion, MK3's don't go rusty if looked after, they are too well made for that, Best bet is to get it sorted out now before it gets too late, also seeing as its inside the door jamb it should be fairly cheap as you shouldn't need to blow the colour in too match to original paint down the side of the car.

The MK2 had a problem if you remember on the little rubber boots that carry the wires into the tailgate, rust would form around the boot and eventually the boot wouldn't have any metal to hold too. the little gromets and boots on cars are terrible water traps and it might be a good idea to go round the car with waxoyl or similar just to give them a coating to prevent rust.

[RossJames]

Seems you are confusing two differenr parts of the sill here.

The clip-on plastic trim along the bottom of the car, as previously mentioned can be bought form your local VW dealer. The meta strip in both of mine had corroded and bubbled.

The corrosion on the actual sill is where the rubber door seal joins at the bottom which can only be seen when the door is open. The water must lie in here an corrode over time. I have found this to be common on numerous mark 3's.

I have repaired both sides on my car by rubing down, treating with rust remover, filling, sanding and respraying, the rubber covers most of the area so a professional job isn't really needed.  My mates Aniversary has the same on both sides as well.