Sill removal.....

[Philpatton]

I know there are lots of ‘how to’s’ for sill removal, but is there a knack to getting the bolts off from underneath the sills? The bolts I’m referring to are the ones that go vertically up from underneath the car into the structural framework? There are 6 per side, and on my z3, all the bolt heads are either too soft to get a socket onto, at which point they round off, or I don’t get any purchase at all on the bolt head. Also, does anyone know what the bolt size is? I’ve tried a 8mm, 5/6th which don’t quite take and a 7mm is too small.
P

 

[colb]

https://www.realoem.com/bmw/enUS/showparts?id=CM12-EUR-09-1999-Z3-BMW-Z3_19&diagId=41_0035
Item No.4 Hex head screw ST4,8X16-ZNS3
https://www.ebay.co.uk/itm/BMW-SELF-TAPPER-ST4-8X16-ZNS3-07119901299-NEW-GENUINE-x5-/153513502710

They either have an 8mm or 10mm head for a socket if I remember when I had mine off looking at the part description I think they were 8mm heads. As a last resort put a slot across them and try an impact driver to break them free enought to use the best fitting socket to wind them out.

 

[t-tony]

They are 8mm screws Phil but the heads are so shallow from new that with time they get even thinner. What you can do is get a 1/4” drive socket and run it on a grinder so the the internal chamfer is ground away and then the hexagon inside will grip the screw head better. Also scrape any under seal from round the screw heads.

Tony.

 

[Mario]

I found that I had to clean those had bolts really clean from any underseal, rust etc with wire brush and even file the seat a bit so it's proper clean, then tap lightly the socket until it seats real good there and they come out fine.