Borrowed from m3cutters

I thought I would have a go at redoing the guide, the old one was old and tired plus had some out of date stuff etc, etc.

Before buying an E46 M3, or indeed any car you are purchasing, you should at the very least learn a little about it. That way, if someone tells you the car produces 400BHp, you know they're lying. Or if they tell you the rear LED lights only came factory fitted after 2004, that again, they're either lying, or just wrong and don't know themselves. In either case, if this happens then you immediately become aware that perhaps other info being given to you by the seller may also be lies or just wrong.

The more you learn, the better armed you will be when it comes to negotiating the best possible deal for yourself when you finally find your M3.

BMW M3 E46 Vital statistics
Engine: 3245cc in line 6 cylinder, 24-valve (4 valves per cylinder)
Power: 343PS (252kW; 338BHp) @ 7900 rpm (Wikipedia)
Torque: 365N-m (269 lb-ft) @ 4900 rpm (Wikipedia)
Transmission: 6-speed manual or 6-speed SMG II Drivelogic gearbox, rear-wheel drive, limited-slip differential
Double VANOS continuously variable valve timing
The 6-speed “full manual” and 6-speed SMG gearboxes are identical. The SMG gearbox is not an automatic gearbox. The only difference between the two is that the normal clutch/clutch pedal operation of the “full manual” is replaced by an electro-hydraulic clutch which is instead operated by shift-paddles located behind the steering wheel (F1 style) or the SMG short-shift stick which replaces the standard manual shifter in the centre consul.

BMW M3 E46 Chassis
Brakes: vented discs, ABS anti-lock braking, DSC (Dynamic Stability Control), CBC (Cornering Brake Control)
Suspension, front: uprated MacPherson struts with anti-roll bar, gas damping (shock absorbers) and 3mm aluminium plated load-bearing raft
Suspension, rear: central location arm, independent rear with double track control arms and aluminium upper wishbones, gas damping, anti-roll bar
Steering: rack and pinion, power-assisted (PAS)
Weight: 1570 kg approx.
Length * width * height (mm): 4492 * 1947 * 1372
Wheels: 18” standard (front: 18x8J, rear: 18x9J), optional upgrade to 19” (front: 19x8J, rear: 19x9.5J)
Tyres: 18”: front: 225/45 ZR18, rear: 255/40 ZR18; 19”: front: 225/40 ZR19, rear: 255/35 ZR19
Body styles: coupe and convertible
See this thread for some more in-depth discussion of wheels, tyres and brakes.

BMW M3 E46 Performance figures
Top speed: 155 mph electronically limited; 174 mph delimited (Wikipedia)
0-62 mph – 5.1s for Manual and SMG, convertible will be a tad slower (~+1/2 sec)
30-70 mph: 4.3 seconds
Standing ¼ mile – 13.3s @ 104 mph (Wikipedia)
The M3 CSL was a hardcore, limited edition version of the M3. It sacrificed the creature comforts of the regular M3 for light weight modifications, better handling and increased power.

BMW M3 CSL Vital statistics
Power: 360BHp (265kW) @ 7900 rpm
Torque: 370N-m (274 lb-ft) @ 4900 rpm
Engine modifications included: High flow carbon air intake, modified valve and camshaft timing, retuned DME (Digital Motor Electronics) (Wikipedia)
Weight reduction modifications included: lightweight exhaust manifold, thinner exhaust piping, carbon fibre reinforced plastic body pieces, carbon fibre reinforced plastic roof, lightweight wheels (Wikipedia)
Chassis modifications included: stiffer, specially developed springs and shock absorbers, improved steering rack, larger front and rear brake discs and callipers (Wikipedia)
Weight: 1385 kg approx.
Wheels: front: 19x8.5J; rear: 19x9.5J
Tyres: front: 235/35 ZR19, rear: 265/30 ZR19
BMW M3 CSL Performance Figures
Top speed: 155 mph electronically limited
0-62mph – 4.8 s
There are some great resources for the M3, which have lots more information and detail:
BMWM Registry
BMW M3 Wikipedia
BMW E46 M3 Datasheet

BMW E46 M3 CSL Datasheet

BMW M3 Model revisions by year

This list is taken from Be sure to check out the website.

2001 to 2002
SMGII available
In-Dash CD Player replaces In-Dash Tape Player (non-Nav cars)
Bi-Xenon option replaces single Xenon
Titan Shadow Trim replaces Gloss Black Trim
Navigation Screen changes from 4:3 to 16:9
Topaz Blue Metallic added as standard colour
Automatic Headlight option
19" Wheels option added (mid year)
Strut Bar added as standard equipment (mid year)
2002 to 2003
Basic Scheduled Maintenance Plan extended from 3/36 to 4/50
DSC/ABS unit moved from rear left of engine compartment under the brake fluid reservoir (leaving large empty space).
Aluminium Trim added as an option
DVD Navigation replaces CD-ROM Navigation
In-Dash CD Player available for Navigation equipped cars
Revised HVAC controls
Topaz Blue Metallic & Steel Gray Metallic dropped from standard colours
Mystic Blue Metallic & Silver Gray Metallic added as standard colours
LED Tail Lights (mid year)
Trunk Handle extended (mid year)
2003 to 2004
BMW Assist (BMW version of OnStar)
Square rear view mirror with BMW Assist and Fin at the back of the roof
2004 to 2005
Laguna Seca Blue and Oxford Green Metallic discontinued
Alcantara available as a standard option
Eucalyptus Malt Wood Trim available as a standard option
Competition (try not to laugh) package (ZCP) added including 19" CSL "style wheels", Alcantara steering wheel and hand brake, aluminium interior trim, slightly larger (front) cross drilled rotors, M track mode for DSC, modified suspension and steering ratio, cruise control deleted. Available starting with 12/04 production.
Interlagos Blue Metallic added for ZCP equipped cars only
Additional information of model revisions can be read here (under “What changes were made during the production of the E46 M3).

BMW M3 Servicing and maintenance

Whilst running an M3 doesn’t cost the earth, it isn’t really cheap either. Though you can now purchase one for under £10,000, it’s still a £47,000 performance car and the cost of parts and services still reflect this to some extent - remember this. This is [sometimes] the reason some M3s have such a high number of previous owners – people fell into the trap of believing they could afford the car because the purchase prices fell into their budgets – only to discover they’re not so happy with the cost of running and maintaining it properly.

Independent specialists are (more often than not) cheaper than BMW main dealers. I personally would hold a stamp in the service book from a well rated independent specialist in as high esteem as a main dealer one. Check out the Dealers and Garages section or search the forum to see if there are any well rated main dealers and/or independent specialists near you.

See below for some useful links.
More information and tips for maintenance
Purchasing tips
Test drive a few cars, try not to buy the first one you go to see
If you’re unsure about whether you want a manual or SMG, try both and do some searching on forums. You’re probably not going to get the hang of it on a short test drive
Get a proper HPI check done on the car. When I say proper I mean one that guarantees the information they provide you and will pay out should it turn out the information they gave was wrong
It may be a good idea to have the car independently inspected. Again preferably by a company that will pay out should they give you some bad information
The last two bullet points count for double if purchasing private or from an independent dealer, and not a main dealer
There are lots of M3s for sale on Autotrader and Pistonheads however I’d say the best place to buy is from a member of an enthusiast forum. It’s sure to be well looked after and hopefully not have any secrets
As with most cars, the M3 has its share of common faults. Whilst not comprehensive the following is a good list of things you should check when purchasing an E46 M3.
Check all service history is present and check the service schedule outlined by BMW has been followed correctly
In particular, check that the 1200 mile running-in service was completed (BMW will not honour any warranty the car may have if it wasn’t)
Wherever the car has had work done, ring up garages/dealers with the registration or VIN number to see if the work carried out pairs up. This should determine if any of the history has been faked
Check the car all over for any accident damage
Check the rear suspension coils – these break easily and are a common fault. A broken spring will fail an MOT. Replacement springs aren’t massively expensive and the labour shouldn’t be more than 1.5 hours for getting both sides done – but why should you pay for it? Get the seller to have it rectified or get the cost knocked off the purchase price
Check when the clutch was last changed. If it was changed a while ago and the car looks or feels like it may have been driven hard then you may have to fork out for this – again try to reflect this in the purchase price
Check ALL recalls have been completed. Cars built pre 2003 had a recall for engine connecting rod bearings. In the case of the E46 M3 I believe this is the only recall
Check the sub frame for cracks and see if any work has been carried out on it. This model is susceptible to a cracked sub frame which gets worse over time. Some main dealers will repair this free of charge – usually by using a foam filler to reinforce the sub frame. Depending on how bad it is – they may replace the whole floor. See this extensive thread for information as well as searching the forum and Google to find out more.
Check the condition of the rear trailing arm bushes
Check the rubber door seals as the glue used seems to be rubbish and can allow them to off. Fairly cheap and cheerful job to repair yourself
Check the rear-view mirror has not leaked of the monochromatic fluid
Check the door mirrors are in good condition and working properly – because they are not cheap to replace!
Check the tyres have lots of tread and at if the car does not have the same brand tyres on all corners, at least check that the car is the same tyre on each axel. Again, tyres are not cheap! If you are looking for some budget but relatively well performing tyres take a look at the Kumho brand (search the forum and Google for ratings)
Check the diff for a grinding noise at slow speeds whilst turning (all the way to full lock). If it grinds it may be a simple problem of the diff not having the updated diff oil which contains additives which reportedly stop the noise completely.
When looking at an M3 with SMG II

Generally the SMG II is bulletproof and is not plagued by the horrific problems found on the SMG I system from the E36 M3, however things can go wrong. Repairs range from a simple relay swap (search for "salmon relay") which costs about £20, to replacing a compression spring within the gearbox which while itself is cheap is fairly labour intensive (as the gearbox has to be dropped) and probably cost in the region of ~£600, to having to replace the pump which I think dealers sell new for about £1200 excluding labour which again is intensive.

Be sure to check the car enages all gears properly, in all modes, at all speeds. In S5 or S6 mode at full throttle, the gear change (do not lift throttle whilst changing) should be lightning fast with a neck-knocking jerk. If the car isn't like that there may be something up with it. The change should be slightly less jerky if you part or fully lift off the throttle in between changing gear. If the seller isn't willing to let you test the car properly I'd walk away. It's understandable if the seller won't let you test in S6 mode, especially on a wet day, as this requires DSC off - which you if not used to handling so much rear-wheel driven power could easily find your self trying to put an M3 shaped hole in a tree.