Quick Links: RACP Differential, M-Clunk VANOS Conrod Other Issues
The E46 M3 has some issues. Best known are the RACP issue, the M3-Clunk, the VANOS-issue and the conrod bearing issue. However there is also a possible issue with the head gasket between cylinders.
Some issues are depending on the date of production since some upgrades took place 6th month 2003.
The issues will be addressed one by one hereunder including recommendations as to how and where to resolve them.
The E46 M3 had a design weakness at the rear suspension from day one – and this weakness was not really addressed in the models life.
The E46 rear axle design includes a sub frame (rear axle carrier) to which the differential and the wheel wishbones are attached. This design means that a lot of forces – both from the rear wheels and the transmission (torque) – are picked up by this sub frame. The forces further needs to be transferred to the body – which is provided by 4 rubber mountings (2 front; 2 rear) and a V-shaped rod.
Unfortunately the anchoring’s of the 4 rubber mountings are too week to take the “punishment” that driving a M3 often implies.
The design were used in all E46s, but the weakness only present itself in the more high powered/high torque models – such as 330D. However, track day racing, “curbing” and “burn outs” on rougher surfaces contributes significantly.
Quite a lot of M3 owners drive around not knowing that they have this issue. The reason is that in the first stages the cracks in the RACP are not noticeable when driving. The cracks normally start at the left rear anchor point, and then spread to the front right and finally to the left front and right rear. In the worst cases cracks and buckling may be seen inside in the trunk – and a bushing may actually tear loose from the body. At the late stages steering may be influenced and sounds may be audible – not to mention that safety is compromised.
Consequently it’s advisable to inspect for cracks regularly – concentrate on left rear and right front. And, of course, get it fixed before it gets too bad and costly - or too dangerous.
Follow the links to see what may be done and where you can find an expert to fix the RACP issue for you.
Link to come
The E46 M3 differential is a LSD (Limited Slip Differential) which provides better traction and permits pretty hard cornering. The LSD function (partial locking of wheel spin) is provided by a stack of friction plates integrated in the differential body. These plates wear over time which partly reduces the LSD function and partly increases play since the plates get thinner. One secondary result of this is that a play builds up at the right outgoing shaft (to the right drive shaft). This play can easily be checked by rocking the right outgoing flange. This is also the cause (perhaps one of the causes) for the so called M-clunk, which is heard mostly when maneuvering at low speed in 1. gear. At higher speeds and gears the M-clunk may be heard, but mostly one does not notice it.
This issue is so common, that some M3 enthusiasts persists that it is not a design fault, but a design feature. Actually you can drive quite a lot with this issue - but it is recommended to get it fixed.
Follow the link to see what may be done and where you can find an expert to fix the differential issue for you.
Text comming
Follow the link to see what may be done and where you can find an expert to fix the differential issue for you.
Link to come
The S54 is a really high performance engine delivering 107 HP per liter and rotating up to 8.000 rpm. This is the absolute top end of engines of that time – and for that sake the top of even modern N/A engines.
This has its price.
The rod bearings in M3s produced untill 6th month 2003 were not as good as later produced models, however even the latest generation represents a weak point.
Follow the link to see what may be done and where you can find an expert to fix the differential issue for you.
Link to come
When I bought my own M3 in Belgium, naturally I test drove the car before buying. It rained that day, but that was the faith of nature. I noticed the M-clunk, saw the small hairline crack at left rear RACP and a few minor other things. However I heard no suspicious sounds. Later, it turned out, I didn’t hear the pinking at 3.000 rpm (especially) precisely because it rained. The sound was so faint that my regular BMW dealer didn’t notice it either when they checked the car back in Denmark – even in no rain conditions. But I heard it – and started to find out what it could be. Hours on the internet just gave a variety of more or less qualified guesses. The local BMW dealers knew nothing.
Other personal M-owner friends really didn’t know anything either – despite their willingness to help.
Note that there were no errors on the BMW-diagnose read outs – not even from the knocking sensors!
To cut a long story short: I got the problem fixed (see the links).
One advice: Don’t buy a used E46 M3 without a compression/leak test.
Follow the link to see what may be done and where you can find an expert to fix the differential issue for you.
Link to come
I have come to know, that there may be an issue with the rear side liftings points. It seems that these points are a bit too weak and may “cave in” somewhat if exposed to excessive loads. It further seems that when they bend, they reach some stronger structures behind and the bending stops. Rumor says that a lot of track cars are in this condition and just let it be as is.
How it happens is not clear. It may be provoked if the car is jacked up at one point, but so much that it lifts both wheels on one side. Another possibility is, that the car is lifted high and then let down quickly – but is stopped abrubtly in the middle of the downward motion. This can many-fold the forces on the lifting point.
