"How To" prevent a corrosion catastrophy

  • So here we have a simple task, everyone is capable of, that could prevent a corrosion nightmare.

    Recently, we have jacked cars using the under sill jacking pads, only to find the jack going up and the car staying firmly on the floor as the entire jacking area crumbles due to severe corrosion around the jacking points.

    So here is an easy step by step method to...


    • Check whether you need to worry or
    • need to take remedial action or
    • Just give it a good clean and some protection.

    Here we start with the sill extensions from my own car. Looking pretty good, if just a little stone chipped underneath on the flat surface under the car.





    Firstly, we need to remove the hard plastic jacking pads (if they havn't already fallen off) with our trusty trim tool. 2 fronts and 2 rears.





    Now, working along the length of the car from one end to the other, use the trim tool to pop out the eight clips (51718108130) along the underside of the trim by using the tool between the metalwork and the plastic sill trim, NOT under the heads of the clips.





    Next we need to remove the rubber seal along the trim under the door opening. You should find that the top surface is stuck with double sided tape (where shown in red) so remove gently are carefully so as not to split the rubber, which is simply pressed in the side to reveal the 5 black expanding rivets (51161881149) circled.







    The easiest way to remove these is to press out the small central pin which will then make them very loose.


    Now, starting from the rear of the sill, use the trim tool to ease the sill off the two rear poppers......





    followed by the front one and the sill extension will now just fall off.





    Red circles show the position of the expanding rivets and the green circles, the underside poppers.


    You can now inspect the condition of the inside of the sill extension, here mine can be seen as VERY dusty.


    But more importantly, you can see if you have any corrosion around the front side jacking hole....





    rear side jacking hole.....





    or, most importantly, around the jacking pad sockets, here is my front one...





    and here, the rear with SHOCK HORROR, a smidgin of surface rust...





    The eight underside poppers clip into these green receptacles (51711932996) shown here..





    and three of the same for the sides.....





    The top edge of the sill extensions are retained with three of these (51711970149) clips which are quite difficult to remove unless you press on the red circled area through the slot they are attached to.





    You now have the opportunity to properly check and treat any corrosion appropriately, wash out any dust inside the sill extension, and check the sill extension for any damage or splitting around the jacking pad mounting points. Here you can see the dreadful neglect on my part of absolutely no polish around this area, with dirt and everything!!






    All joking aside though, this is a very important preventative maintenance task, and you can see from this last pic how body spray wax, as used inside panels, has protected my car where I have previously applied it. (yellow yucky looking drips)





    I have now thoroughly washed and treated the entire sill areas and had them repainted in a rubberised stonechip coating in body colour before refitting the sills with all new clips and fixings.


    Quantities quoted are per side apart from the jacking pads which are per vehicle.


    This is an hours job at max and could save thousands in welding and structural repairs.


    8Tech.

  • Thanks Gerry - this is a just in time warning. For some it may already lead to a fair bit of work.


    Gerry has shown the tools to remove the various clips and fasteners. Better go and get a kit like shown before



    No tools?
    The jacking pads come off easily pulling down & out from the inside to the outside. Take notice which one goes where! Already missing or broken? Part numbers: 5171 8108301 and 302 at less than 10 quid each.


    The lower round clips of the side skirt also come off by pulling the skirt down forcibly. They get brittle and do break occasionally - 5171 8108130 @ maybe 40p each
    The inner ones, especially at the front and rear end of the skirt may require significant force. Don´t be overly worried - those side skirts are really tough.


    Gerry did not yet tell that in order to reinstall the rubber seal which hides a few rivets (the frontmost ones quite hard to get back in) one best removes both (where applicable) sill covers.
    Especially the chrome strip on the rear one may else destroy your rubber seal when pulling too hard. Those seals are not cheap and the ones you get are 20 years old with a defunct double sided tape, so nothing to be gained in not keeping the old one, attaching double sided tape and refitting those.
    The punch through rivets are 5116 1881149 @ less than 20p each.


    The upper part of the door sill cover also holds the door latch striker fastened with 2x Torx 35 (or similar) and attached to a plate which will fall down (inside the body!) once the screws are completely removed & if no precautions are taken. Precautions: magnet and an additional pair of hands or remove rear interior cover and punch a hole through insulating tar paper - this way one can easily get to the plate - even if lost.
    Both sill covers have various methods of fixtures, clips, glue, key & slot. Be prepared to buy a bag full of clips (5147 1840960 @ 25p ea) this time and work your way carefully up there, especially where the two sill cover parts meet.


    It reads more difficult than it is though - can be done by everyone including hyperventilating Canary Wharf bankers :aetsch:


    Is it worth it?


    As Gerry says - there might be a smidgin of rust..... IF... your car has been pampered and kept garaged all its life.


    If not. Well. A smidgin here, a wee hole there...


    This is what we saw last year on the very last produced 8er CC67485. That was more than surprising but no reason not to tackle it.
    Underneath the side skirt - a neat little hole. No explanation how it got there but was glad having gone there!


    Underbody protection with cracks and rust developing underneath



    Jacking pad socket



    Lower edge of doors



    Rear wheel arch



    Spare wheel well - especially notable with ex factory headlamp cleaning system



    Underneath boot rubber seal




    Underneath rear bumper - came to light only after removal of undercoat with chisel:


    This was after 50k mls and 12 yrs in the UK at unknown storage conditions.


    If you can´t store your car dry & ventilated but have to resort to leaving it outside be prepared for this and much more. Unfortunately the 8er does not cope all that well with continued exposure to the elements and as Gerry has pointed out - if you want to keep the E31 for a while to come don´t be shy and look after those spots rather now than later.


    Cheers
    Reinhard

  • Well you saw the horror I found after 21years in the UK. As Gerry said not a massive job and once checked or even repaired you can smile again. I have only check and repaired one of my sides. I had planned to do the passenger side in prep for Duxford (sorry again guys) as I have replacement covers which I got on ebay 4 years ago for 99p waiting to go on (current ones are chipped etc).
    I fear rust as my car for the last 6 years that I have owned it has never seen a garage at night other than a petrol garage that is:harhar:

    :driving2:Its been a year since I sold her and I still miss her.......





    Lloyd

  • A quick note on Reinhard's images regarding the rear wheel arch.
    I had a couple of tiny little bubbles there so I asked a shop for a quick smart repair on those corners.
    As they removed the paint, they found more and more rust. :ahhhhh:
    As it turns out, this area is actually rusting from inside out. :banghead:
    (Probably due to water entering the rear side panels via the weather strips on the rear windows.
    With the rear windows closed most of the time, there is no ventillation there and it stays damp.)

    I insisted on a quick repaint but the paint shop guy told me that the bubbles will be back in no time... he was right.
    So, this summer there will be some cutting and welding to be done...

    Cheers,
    Steve

  • Thanks for the info and pictures Reinhard. I reckon Steve is right about the rot starting from the inside, my blue 840ci produced a 'damp' sort smell when the rear windows were dropped - probably not a good sign.

  • I can only confirm Reinhard's discoveries, my CC67347 had all the issues he has highlighted, plus a few others,

    If you take the sill covers off, take the time to look at the fuel and brake pipes - these corrode, particularly near the wheels.
    Also look at the wheel arches from inside the arch (use a mirror), the plastic liners should have a rubber edge strip, but once grit gets between those and the metal abrasion can occur.
    The sill covers can also rub on the lower edge of the metal wheel arch.

    Cheers

    MB

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