Sorry to thread jack this...
I'm in pretty much the exact same position as the OP and since this thread is fairly recent I thought it was relevant...
I'm in the market for an E55K with a budget of around 10K as well.
I went and had a look at this car today:
Used Mercedes E CLASS (211) E55 AMG 53 Plate for sale - PistonHeads (Ref 985576)
It's a great spec with distronic, dynamic seats, command, electric rear blind and factory bluetooth.
On the plus side the disks and pads and tyres (Contis) are all new.
The car was sitting nice and level when I went to see it and it hadn't been started that day (I asked the seller not to).
Firing up from cold it was a bit noisy for 30 seconds or so but to be honest I haven't heard one start from completely cold so it may be fine. It sounded a bit like how worn power steering pump sounds, a whirring sound... As I say though this went away after 30 seconds or so. Otherwise it all seemed fine.
Under the bonnet was a bit grubby and some things were a tad corroded. The S/c belt pulley that's visible has some corrosion to the pulley. Not sure how critical that is....
The SBC looked very much original as did the rad. Both those things concerned me a bit.
Due to some ineptitude on my part (I went by Motorcycle) I only had bike boots on so couldn't drive myself but on the testdrive there were no apparent knocks and the car rode nicely. Performance was 'adequate'
My concerns other are...
The drivers seat bolster is pretty scuffed up with some of the thread missing on the double stitching. I don't think there's any risk of it coming apart but it looks ugly to my eyes and would bug me every time I got in and out. The bolster on the drivers seat base was OK. Not perfect but not as pushed down as some that I've seen. The rest of the leather looked good and wasn't dry or cracked.
There was slight scuff to the front bumper which would need a repaint to be perfect.
Generally good paintwork otherwise with some stonechips on the bonnet but all in all it looked fine.
I couldn't find any rust...
One question I have is whether the wheels should have a diamond cut face to them? These were silver painted... There were a few marks so again a refurb would be needed to get perfect but they were pretty decent all in all.
In terms of the paperwork there was a duplicate service book with some pretty sketchy looking stamps in it. They didn't seem to relate to any of the invoices which was weird.
The seller said that Mercedes had confirmed a full history up to 38K after which it had had a service at the garage of the guy who owned it previously (some kind of race prep engine builder firm) at 46K and then the seller had just had it serviced at 58K (oil and trans fluid) by the same garage (as the previous owner)
Is it possible to verify the history with Mercdes at all?
Any input gratefully received....
To me the history and seat bolster could be better and the SBC and rad are both possible problems plus there is a bit of money needing to be spent on tidying generally.
If anyone wants to suggest any alternatives please do...