Hi, this was my post a while back on a similar topic hope it helps...
"Remember no matter how reliable a car can be it's a M3 you want to buy. It was certainly not ben driven by Miss Daisy, its likely been hammered but these car's where built to be hammered Clap.
First thing you should look for first is getting one with the lowest mileage "be careful it could have been changed' and with a motorplan. Go to a dealer along with the cars VIN no. they give you the entire history on the vehicle. If its been in a smash, major components have been changed like the gearbox, diff, engine, computer box ect... Also stay away from one that been modified, it's likely to have been dragged at least once in it's life.
With regards to the gearbox, i know that the both 6 speed and SMG are great. However the SMG takes some getting used to. Like with the manual the clutch on the SMG has to go sometime but also it does act up now and again and a simple software reset cures the problem. The relays on SMG do pack up often and once they do the car cannot move as the gear lever gets stuck. Price on the boxes differ by like R20000 brand new, but i don't know whats the prices to get them repaired.
However the engine is bullet proof, i can only recall that the vanos does often leak oil and BMW will not repair them. I remember a few years back it cost R30000 to have it replaced but lucky for me my car was still under motorplan. I know guys do sell overhauled ones but i don't know the price of them. Diffs are also prone to breaking, again depends how them car was previously driven. The control arm bushes also need changing especially for the SMG M3's and the interior trim panels on the A pillar don't last they cost R3500 to replace. Breaks also tend to get worn out pretty quickly, again it depends how you drive the car, but they tend to make a lot of noise and cause heavy break shudder under high speed when they get close to needing a change.
As for the tyres, like with any rear wheel drive car thay are hard on the rears. But decent driving should get you at least 20000 odd kms.
Please don't think i'm bad mouthing the car I did own one myself a while back. As these things are unlikely to happen on the first day all i'm saying these are the common faults on them, you wanted to know the maintenance on them
. I don't really have to comment to the positives of the car its an M3 after all and that name should tell you what to expect. But i regret it selling mine and wish i kept it, bugs me every time i see one :bawling:"
