Yup, I had an 840ci sport. Great car, just not as fun as the Z4.
Here's a copy and paste from a pm to someone else who was asking about them.
I would be sure to go for the sport, so it has the csi body kit and sport suspension. Front bushes wear quickly, not always easy to tell whilst the car is standing. Often I results in wobble through the wheel around 55mph, or under braking. Warped discs aren't uncommon, nor are the usual broken springs like other BMWs.
The rear screen often goes milky in the corners. Cars that have had the front windscreen replaced often get rust around the frame. The sunroof is another common rust area, usually means replacing the panel and it's seal.
If it has the Edc suspension, it's bloomin expensive to fix... Best go for one without.
The rear suspension mounts can tear, check around the inside of the boot. Seems to be more of a problem when people have fitted large wheels. There are plates available to bolt onto the top of this area to help spread the load (I have a pair I should sell actually)
The computer display often has dead lines of pixels, not cheap to fix. Check the passengers mirror dips when reversing, as long as the adjustment switch is in the right hand position.
The engines valve cover gaskets can seep oil around the bolt holes, it's normal, if it's bad the spark plugs can get covered in oil.
I think that covers most of it...
They are no worse for repairs than a similarly aged 7 series. Some of the parts are less common, body panels mainly, but there are plenty being broken up for spares on ebay.
850 Csi's are obviously going to be more expensive and tbh I'm not totaly convinced about having a manual in one, it's not a car I'd hussle much.
If I could afford my dream car collection, there would definetly be an 8 in there.
