Rusty rear inner arches

[mcjjordan]

So as title sugests ive found some rot
Mainly behind the seat ,
Can anyone whis tackled this give me any pointers?
Is it oatchable or best to replace complete arch?
Any good write ups?
How involved is the strip down?
Is it best to just bite the bullet and send off to a pro ££££?

The more i look at it the worse it seems to be ...

[uwbuurman]

Lateron, somewhere next week, I will awnser this question extensively. For now, just look in my english 323i topic, to see how much work needs to be done when you want to replace them complete.

[BertjeConti]

uwbuurman did the job how it should, cut out the whole inner wheel arch and replaced it. He knows all about the E21 shell.

Such a repair is only possible when the car is dismantled completely. If your plan is only repair the worst rotten pieces and drive the vehicle for some more years, some patchwork is also possible

I've had some similar rot in my E12 shell and patched it up, so it holds another few years. Rear wheel arch build up of E12 are very similar to E21.
The cause of the rot is that the shock towers have a hollow space (second reenforcement sheet), as you can see in my pics below.

here's my patch work, not uwbuurmans way of repair.

very strange thing, my car wasn't wet inside,while the rotten hole was fairly big:


all rot cut out, clearly visible is the hollow space now:


first fresh piece tacked in:


second piece tacked in:


third piece tacked in:


view from outside in wheel arch:


then make it rust proof, paint, seal and paint again.
preserve hollow space for more rust damage.
done

[uwbuurman]

Indeed, what Rob did, is the best way to repair incase of patchwork. Nothing wrong with that.

The replace the inner arch complete, you do nog take the whole of the car apart, but a large part. You can not fit the rear inner arch without making a cut of some 2 inches in the bootfloor.

[Vic]

Hey guys, whilst on this subject, uwbuurman would the outer panel need to be cut IF I wanted replace the inner and outer rear arches. My outer is rusted on and about where the mid section chrome strip attaches to the body- a very common area as we know. A body shop says he can remove the spot welds from the existing archs panels and replace the inners with removing the outside main skin, is that possible?

Thanks a lot for your advice!

[uwbuurman]

It is possible, if you keep the outer arch complete, you dont have to cut open the sidepanel, at the sill.

Look in my topic, after the sidepanels were replaced, i replaced a corner of the outer arch, because of the new side panels I did that from the other side.

The inner arch runs BETWEEN the inner and outer sill/bodypanel.

Exactly the part you want to cut of so you can put in the outer arch without cutting the side panel, that corner is always rotten...

The thing is, getting the outer arch out, will most definetly give problems at the wheelarch, where it is spotwelded also.

All in all it will be a crappy job, with lots of little repairs needed. It will be a hassle also to get the pipe that runs the airhose from the tank welded back, since that is welded on the outside of the wheeelarch, before the side panel goes on. It can be done, but Not very easy.

Inner arch, the square platen runs between inner and outer sill



The outer arch



To understand better what I mean, just look in my topic at around page 14.

[Vic]

You're a great man, given really helpful guidance, will reply later after discussing with a body shop this week. Thanks for the indepth detail and positive advice! Really appreciate it

[uwbuurman]

No problemen, always prepared to help a fellow BMW enthusiast! Want to know more? Just ask.