The E46 M3 has truly reached cult status amongst car enthusiasts in all its forms. It makes for a fabulous hooligans delight retaining that rear wheel drive analogue feeling we love. It rewards us with incredible usability and affordable running costs if the right due diligence is done as part of the initial purchase.
The E46 M3 was at the bottom of its depreciation curve about 4-5 years ago, hence some examples ended up with slightly dubious owners and many of the exceptional low mileage examples went in to long term ownership.
We have an order book full of potential M3 buyers. Finding cars for these people is proving very hard. It is very easy to forget the age of the E46, both sellers and potential buyers are guilty of this. I cannot tell you how often I hear the words "my car is 100% rust free". I then ask when they last looked underside and checked the car for surface corrosion.
The underside rear end of M3s are suffering from surface corrosion around the fuel tank and rear bulkhead. An Achilles heel design made worse by a lack of factory seam-sealer that has also carried on to the next generation of 3 series.
This surface corrosion, if caught early enough can be nipped in the bud. We are now having to carry out substantial welding and fabrication to some examples visiting our workshop. We wish we had got to see these cars 2-4 years ago when preventive maintenance was all that was required.
We are inundated at the moment with E46 M3s with cracks in the boot floor. These are stress cracks caused through power being transmitted to the differential and then in to the rear sub-frame causing cracks to appear around the sub-frame studs in the floor.
We are seeing some terrible attempts to rectify or just hide this problem. Usually these attempts at cheap cover-ups are made by people trying to sell an E46 M3 for a top price, knowing they are misrepresenting the car. We have seen these cracks simply covered up with seam-sealer, heavy layers of cavity wax and even seen attempts to weld the cracks with the rear sub-frame still in situ.
There is only one way to do this repair properly. Remove the exhaust, prop-shaft, fuel tank and the complete rear sub-frame with all suspension and differential. Once all this is removed to gain access, any corrosion can be dealt with at the same time and the reinforcing repairs carried out properly. Once these repairs are finished, the original factory products are used to ensure the factory finish and colour to the floor of the car are replicated perfectly.
These pictures show how the repair should look once completed.
Please, please do not let any of this put you off. All of us at Classic heroes’ love the E46 M3 and it is arguably the most all round M3 of all the variants.
The point of this ramble is to ensure that current owners get the underside of their M3 checked thoroughly for both cracks and corrosion and potential new owners do not forget that these cars are rapidly approaching
20 years old. They are all now at a time in their life, that they need both preventive and age related maintenance. It's time they were treated to a birthday to ensure another 20 years of hassle free motoring.