The reasons E-class W124 sills rust

[big x]

Not my car but typical of the rear jacking point...The rust has been ground out in the first pic.
The second car has had the surface rust treated before it gets to bad.

This is what I've come up with bearing in mind internally the sills are well protected with wax.

1) The area around the tube flexes when the jack is used and cracks the paint.The weld itself doesn't rust but the sheet metal of the sill in contact with it does.With time this spreads out in a circular fashion.This is external corrosion.
2)The plastic cladding (removed in the pics) means the area remains damp throughout the winter.
3)The different properties of the sheet and weld metal may by itself cause corrosion.
4)blocked sill drain holes can make matters worse.

Funnily enough a car may well pass an MOT in this state.Testers don't remove the plastic cover and (I may be wrong here) a holed sill is ok as long as it's not within 30cm of a structural mounting point.The rear subframe mount is a little bit further back than that.The rubber jacking block support structure is still intact in the first pic. If this was rotted out you would have big problems with repair access.

Anyone know how much a repair of this area would be..maybe nick froome may know ? A sheet with a hole in welded over the sill should do it.

adam

 

[bolide]

The MOT tester won't look. There's a limit to what he can do to find holes. And it's probably too far away from a suspension mount to worry about

I wouldn't think it'd cost more than £50 / point to sort. It's just welding & priming - an hour each? It'd probably take longer to remove & refit the trims than do the job

Nick Froome
www.w124.co.uk

 

[Ian B Walker]

I had a 190E done at Mb Blackpool with exactly the same problem. It cost me £150 and I couldnt see the repair afterwards. First class job done.

 

[big x]

Yes, an external patch is quite straight forward but it's poor engineering that it can happen in a 1994 car. You wont find a 1994 C-class like this (from what I've seen) they changed the design of the jacking point.
In the long term I think these cars are going to be written off
when the area at the back of the sill, where it joins the floorpan,
rusts through.This is right at the subframe mounting point.Unless the
car is a coupe or diesel estate it won't be an economic repair.
Anyone with a W140 S-class should treat the jacking point with antirust
treatment as I've seen early cars going the same way.

adam