E46 Buying Guide.

Here’s some of the things I’ve gleamed from the internet, with some of my brief personal experiences, now I am in my 3rd E46 Coupe, and my 2nd M3

Front Wings.
Can be prone to rust, owing to dirt getting caught between the inner wing liner, and the edge of the wing. Get the inner liner out, and get it cleaned.

Rear Arches.
The same as the E36, watch for trapped dirt that causes the arches to rot out.

Boot Lock.
I have noticed paint starting to bubble around the boot lock (where the key goes in)

Rear Bulb Clusters.
The clips on the rear cluster are delicate, and are prone to snapping, not a big issue, but if they are attached with zip ties or tape, they can rattle, New ones are roughly £35 each.

Rear ¼ Window Seals.
As with the E36, the rear ¼ window seals seem to perish. But unlike the E36 they are about £250!!!

Rear Springs.
The rear springs are known to fail, and I can confirm my current car has recently had a set @ 44K, and my last E46 M3 had to have a set of front ones, I can only assume if you’re running a set of 19’s with the stiff suspension setups of the make, they come under a lot of abuse.

Door Seals.
The E46 coupe generally as an issue with its door seals, as they can move and get damaged over time, where out or just split, and as they carry a heated element, they are expensive to buy, circa £225 + vat last time I checked. The M3 seems to have an issue that the trim separates from the seal, thus looking a mess, again, something my current car has fallen foul of.

Noisy Diff.
The diff’s on the E46 M3 can make a scrubbing noise when making tight slow turns, like reversing out of a car park space. Mine does this, I tried the fix, which was the latest BMW supplied Diff Oil @ £90 + Vat+ Fitting, and though the old stuff was minging, it still makes the noise. My garage advised me not to worry about it. Research on the net will tell you all about the reasoning.

Oil Pump Connecting Rod Bearing Kit - The Major Factory Recall.
There was a service recall for the Oil Pump Connecting Rod Bearing Kit, if the car you are looking at was subject to the recall, ensure it was done, as well as the running in service @ 1200 miles.
Quote from the net “
"The problem has been identified as contamination of the engine lubricating system during assembly in combination with unfavourable tolerances in the engine oil pump for the M3 coupe/convertible produced from October 2001 through February 2002.

Alloy Wheel  up size options (from Net)
Yes, the correct upsize is 245/40/18 front and 275/35/18 rear for 18" wheels and 245/35/19 front and 275/30/19 rear for 19" wheels. Many have done this on both stock and lowered cars without any rubbing issues. 

SMG Additions.
I personally have been very lucky with the E46 SMG so far, but they can be problemattic. From my internet research and recent personal experience I can advise watching for the Cog Warning, which could be any generic SMG error, which in my case was the Gear Position sensor, which tells the ecu what gear the car is in I guess, and these are just shy of £300 plus fitting, which can be done DIY, and there are some good articles on the net, but my Indy did a good job. Then you need to have the adaptations ran using the BMW software, again dealer or Indy with INPA or similar can do this. My advice is get BMW to run the diagnostics, so you know where you stand

The salmon really can also fail, which is a cheaper fix, under £15, but to get to it you need a torx T25 screw driver, and its located in the fuse box under the bonnet top right hand corner

Also check the SMG Fluid levels, as if they drop the car can spit out gears, and if you have assess to BMW diagnostics, check the pressure of the SMG pump is working parameters, again a lots of info from this specifically on line.

As many car owners have odb diagnosis tools, may be worth having a look at the fault codes on the car you look to buy to see if they is any error message hanging around, as I bought a car once that got a fault 5 miles into the drive home, and it kept coming back, so the owner had obviously just cleared it prior to my test drive, so be wary, on BMW's warning lights can mean cash needs spending