Have you checked your sills yet?

[Bumpa]

I decided to look at mine, not because there was any obvious problem, but just because the car is 16 years old and made of steel. Am I glad I did! Once the cover sill was off the extent of the corrosion at front and back ends on both sides was alarming. It seems to stretch from the jacking points to the ends in all cases. However, once I had attacked it with a wire wheel on the angle grinder, followed by a small granding stone on the Dremel, I could see that the metal wasn't badly compromised - yet.

I gave the cleaned metal a good soak with Fertan, then when that had done its work, I coated them with Dinitrol underbody wax coating. The cover sills had surface corrosion on the inside, so they were scurfed down and painted with black Hammerite inside. I then used my compressor to spray inside the box section with Dinitrol cavity coating through all the very handy holes.

It's all back together again now and looks no different to what it did before, but at least I know it should last for a few more years now.

 

[Davyhoogy]

Good job. This catches alot of people out myself included and the only notice you get is the one that says it's too late.
Are your sill covers ok? I had to order new ones from bmw at £150 a side

 

[Bumpa]

Yes, the sill covers weren't bad. A small area on the front of the right hand side one, but I was able to make a repair. Since the damage was on the bottom edge, the repair is not at all noticeable. I'm happy to say my car looks as smart as ever.

Estoril Blue Metallic 335 paint is no longer available from BMW, so I bought an aerosol from The Scratch Doctor on ebay, not knowing whether it would be close to the colour or not. Amazingly, the paint is a perfect match and really can't be distinguished from the original. Very pleased.

 

[Bozzy]

Job well done @Bumpa . Looks like you caught it in time.
@Sean d fitted new ones for me a few years ago, when he got the old ones off a load of compost like soil dropped out, trapped in by the sills. Luckily the main structure and jacking points were ok.
So as you rightly point out, well worth checking.

Steve.

 

[Bumpa]

The rubbish that can collect inside the sill cover is due to gaps between the plastic wheel arch liner and the sill cover. I have blocked these gaps with non-setting windscreen sealer in an attempt to keep stuff from being pushed in there by the tyres.

 

[DrWong]

I'm in the middle of sorting mine at min. I'm aiming for total rust removal so it's taking me bloody ages. Mine were prob in slightly better condition than yours but similarly mainly crusty from jack points to ends. This is what driver side looked like after being attacked with a polycarbide disc in an angle grinder

I then applied a coat of Bilt Hamber Deox citric acid gel. This stuff is amazing. Just apply, cover, and then wire brush off when you come back and the rust just dissolves away leaving clean metal behind. This is after one application, left overnight (other sill though):

After a second application left on for three days all the black pits were gone apart from a few tiny specks. It's on the third application now. Once the metal is all bright and shiny, it's getting epoxy primer, seam sealer, stone chip, colour coat and then lacquer. I've also got BH cavity and underbody wax aerosols with injection lances for afters.

The trouble is I've discovered tiny blisters on both sills under what appeared to be good paint, that when prodded a bit harder with a screwdriver reveal rust underneath. So I've basically resigned myself to rubbing down and epoxy'ing the entire lengths of both sills now

 

[Nodzed]

I decided to look at mine, not because there was any obvious problem, but just because the car is 16 years old and made of steel. Am I glad I did! Once the cover sill was off the extent of the corrosion at front and back ends on both sides was alarming. It seems to stretch from the jacking points to the ends in all cases. However, once I had attacked it with a wire wheel on the angle grinder, followed by a small granding stone on the Dremel, I could see that the metal wasn't badly compromised - yet.

I gave the cleaned metal a good soak with Fertan, then when that had done its work, I coated them with Dinitrol underbody wax coating. The cover sills had surface corrosion on the inside, so they were scurfed down and painted with black Hammerite inside. I then used my compressor to spray inside the box section with Dinitrol cavity coating through all the very handy holes.

It's all back together again now and looks no different to what it did before, but at least I know it should last for a few more years now.

View attachment 90337

View attachment 90338

Had a similar issue this is a mod I did to my M, may be of interest?

https://zroadster.org/threads/mod-how-to-stop-the-dirt-getting-into-your-sills-maybe.21808/

 

[Bumpa]

I like that Nodzed. Very neat. I might make some for my car.

 

[DrWong]

Quick update - passenger sill after fourth application of citric gel. Horrifically pitted but virtually rust free and still sound metal. Few tiny specks remain by the screw hole but one more lot of gel should get rid