Prologue: The E46 M3 in 2019

The year is 2019, and you are on the hunt for excitement. You’re looking for something fun, striking, and not too hard on the wallet. You shop around, check out what your favorite manufacturers have to offer, maybe take a few test drives, but nothing is clicking. You’ve nearly resigned yourself to just buying something you thought was ok and learning to love it. Then, one week while you’re out shopping, you see it. Maybe it was driving down the highway. Maybe it was parked at the gas station. Doesn’t matter where you see it, something about it evokes a childlike sense of wonder and excitement. Suddenly, you know exactly what you want, you’re going to fulfill a dream you forgot you’ve had since 2001. You’re getting an E46 M3.

Table of Contents:

Introduction / Maintenance…(page 1)

Introduction

Whether you are a fan of BMWs or not, if you are any kind of enthusiast there’s probably a little (or massive) wish in the back of your mind that says “I’d love to own an E46 M3”. When you’re at a meet and a clean E46 M3 rolls up there’s always that short conversation of “Man, I still want one of those” followed by a chorus of “Oh for sure” and “yeah same”. We’ve never really met anyone who has owned or currently owns an E46 M3 who truly regretted it beyond maybe being unable to afford the maintenance on it (which can be a little steep depending on how well the car has been cared for). It’s something you’ll find most enthusiasts admiring on some level. It’s just a solid car with a good heritage, impressive engineering, and a timeless design.

Maintenance:

This subsection is intended for new M3 owners or those who are worried they may have forgotten something major. If you have had yours for a while and have addressed a lot of the M3’s common issues then just skim it to make sure you have been properly maintaining your vehicle.

The E46 M3 was produced from late 2000 up to mid 2006. This means that if you buy the absolute newest one you can find, you’re still purchasing a 12 year old vehicle. While this is not particularly old, it is not new by any stretch of the imagination. This means that in most cases you’ll be looking at well over 100,000 miles, sometimes closer to or surpassing the 200,000 mile mark (less likely with a performance vehicle like this vs a common commuter car). A lot can happen in that amount of time and over that kind of driven distance. The first thing you should do is make sure the car is mechanically sound before you dig into the heavy modification.

-Basic Maintenance:

First you’re gonna want to get yourself an OBDII scanner and check your car for codes. Do this even if your check engine light isn’t on. This is to check two things: 1) it will tell you if your car has any trouble codes, and if it does then that also tells you 2) the bastard who sold you the car removed the check engine light bulb or something of the sort. If you have any fault codes hopefully you got yourself a scanner that is nice enough to tell you what they mean. If it just gives you a P#### number then pull up the ol’ web browser and do a quick search for that code along with E46 M3 or 2001-06 BMW M3. You’ll be greeted by plenty of people with the same code and what they did to fix it. If you’re not very confident in your tinkering abilities take it to a shop, but we still recommend checking the codes first and looking over the car thoroughly beforehand so if someone tries to sell you something you don’t need you can tell them to shove it.

After checking all the codes you should check for mechanical faults not indicated by the engine codes. Gaskets will leak over time so check your engine bay for oil residue. It is usually a good idea to change gaskets on a motor that is new to you just so you can be confident in how long they’re going to last.

-Preventative Maintenance:

Once you’ve addressed any issues present with your car you’ll want to think about some preventative maintenance. In other words this is stuff you should repair or replace so it doesn’t fail on you when you’re driving it. Good things to check include:

-Full oil change and new oil filter

This should be done regardless of how recently it was done by the previous owner for various reasons. What if they’re a liar? What if they used cheap oil because they knew they were selling the car soon? Unless you have a dated invoice from a reputable shop that shows when the maintenance occurred and what oil/filter were used, you should be changing the oil immediately regardless of what the previous owner says.

-Air Filter

If you’re not buying an aftermarket intake we recommend inspecting the filter in your factory intake box to see if it’s dirty. Replacement filters are very cheap to replace and your engine will be much happier if it can breath freely.

-Brake Rotor Condition / Pad Thickness / Fluid

Your brake system is the one of the most important things to maintain on any vehicle. If your engine dies or your battery fails you can still coast yourself to safety, but if your brakes fail while you are driving you are in for some trouble no matter where you are. Therefore it is prudent to properly maintain your brake system for your own and others’ safety. Check that your rotors are not cracked and do not have a lip at the edge (a telltale sign that they are pretty worn down). Check that your pads have plenty of thickness left (gauges can be purchased to test pad thickness, or you can eyeball it if you know what you’re looking at). Finally, get rid of that old brake fluid. Depending on how old it is it can have lost a good deal of its heat resistance or developed bubbles (more info in track section). In the interest of not crashing your M3, at the very minimum do the safe thing and change out the fluid. At the very least bleed the system to get out any bubbles, but a full flush with some new DOT4 brake fluid is recommended. If you want an easy all in one brake tune-up/upgrade we do have full brake packages available that come with pads, rotors, fluid, and even stainless steel brake lines (for improved heat resistance and pedal consistency. These kits are available in variants depending on if you want blank, drilled, or slotted rotors.

-Drivetrain

Depending on how many miles are on the car you probably want to check on your clutch, pressure plate, and flywheel. This particular part is hard to gauge wear on because it is highly dependent on the skill of the driver and/or the conditions the car was driven in. If you get an E46 M3 with over 100k miles and no record of a clutch change then you should definitely plan on changing it very soon, that is nearing the high end of clutch life even taking conservative driving into account. Your clutch should give you a fair bit of warning when it needs to be replaced so keep an eye out for the following:

Higher engage point – you’ll have to release the clutch pedal further than usual before the car starts moving
Clutch slip – if your engine’s revs increase without an increase in speed while your clutch is fully engaged
Judder – vibration when engaging the pedal (unless the car is equipped with a 6 puck clutch or similar, then that is just natural behavior)

If your car is experiencing any of these symptoms you should consider replacing it. An OEM style replacement won’t cost you too much and will give you peace of mind knowing that’s something you don’t have to worry about for a while. If you want more of an upgrade you could consider something like the ACT HD clutch kit which gives you the option to choose between several clutch disk options depending on your desired clamping force. If you aren’t going to be adding much power to your M3 we suggest just going with a street clutch (or solid street clutch if you’re some kind of masochist). At the very least get your clutch diagnosed at a shop if you’re worried that your it is on the verge of failure.

Other signs of necessary drivetrain maintenance:

Spongy clutch pedal feel – may feel fine initially but become spongy as the car heats up, indicating a failing clutch line (assuming you’ve bled the system already)
Constantly spongy pedal – may indicate master cylinder issues or air in clutch fluid
Clutch doesn’t fully disengage with pedal to floor – clutch linkage may need adjusting

-Rubber hoses in engine bay

Over time heat from your motor will dry out various rubber hoses and lines in your engine bay. If you’re super thorough, best practice is to replace every coolant hose and vacuum line you can find. If you don’t have that kind of time or patience we recommend a thorough inspection of the rubber components and replacing those that feel dry or stiff.

-Coolant Expansion Tank

On the E46 M3 it is common for the plastic coolant expansion tank to crack from old age/engine bay heat. You can replace it with a new factory piece or if you want to spend a bit more a few companies make aluminum versions which will be much more durable, and look pretty cool as an added bonus.

-Chassis Reinforcement and Repair

This is covered more in-depth in the “Performance Maintenance” subsection below, but it is not uncommon for chassis damage to occur even when the car is driven conservatively. We suggest at least inspecting or getting your car inspected for subframe, trailing arm mount, and strut tower cracking. Better to find the problem early and address it than to have a huge failure later on.

-Performance Maintenance:

If you’re going to be driving your M3 as it was intended (fast) there are certain things you’re going to want to address. This subsection covers components that affect the car’s performance but aren’t included in our Preventative Maintenance subsection due to their spirited nature.

-Bushings

Bushings are little bits of rubber used to reduce the transfer of vibrations between certain parts of your car. On the E46 M3 there are 4 sets of bushings in total and each of them is a potential point of annoying issues. Factory bushings will, over time, deteriorate and start allowing more flex in the suspension. This gives steering and road feedback a dead feel and will hamper your car’s responsiveness, as well as causing issues with your rear subframe. When replacing your bushings you can either use new factory rubber bushings or you can opt for stiffer but much more durable polyurethane bushings. Polyurethane bushings allow less flex than normal rubber factory bushings so your ride quality will suffer slightly but the benefits are tighter handling feel, better alignment consistency, and more information being relayed to you through the chassis and steering wheel. If you’re tracking your car these will make your life better in so many ways, we can’t say they’re required but they are highly recommended.

Front control arm bushings are your main connection between the chassis and the front wheels. They are responsible for isolating vibrations from the front suspension. When these bushings get old they will allow for more flex which means during braking or hard cornering your suspension arms will flex too much, meaning your dynamic camber and toe settings can get thrown off (see alignment subsection for more details about the importance of a proper alignment). With a new set of polyurethane bushings you get consistent road feedback and suspension geometry so you only have to worry about your own driving skills and not whatever weird stuff your suspension may do when you brake or hit a bump mid corner.

Much like the front control arm bushings, the rear trailing arm bushings help to keep your alignment geometry consistent so you get clear and solid feedback from the rear suspension. This keeps your car from making unexpected lurches under acceleration or cornering. Ideally you’ll have both sets installed so you get more consistent alignment at all four corners.

The differential mount and rear subframe bushings kind of go hand in hand as both sets interact with one another. The subframe bushings connect the subframe to the chassis, and the differential bushings connect the differential to the subframe. Both together are the connection between the differential and the chassis. The reason you would want polyurethane versions of the bushings is that they will reduce amount of flex induced by acceleration so you get better power transfer to the wheels. The other more important reason you’d want to change these out is that excessive flex from the drivetrain is tied to the dreaded subframe cracking that plagues the E46 chassis (see “Weld-in Chassis reinforcement” subsection later on this page for more details). Just be aware that these will increase NVH due to having a more solid connection between the engine and the chassis through the subframe. Also note that both sets should be the same compound (e.g. 75D subframe bushings pair with 75D differential bushings).

-Bolt-in Chassis reinforcement

One of the biggest problem areas of the E46 M3 is definitely its chassis. The rear subframe, strut towers, etc. can all experience failures from normal driving and are very likely to experience issues if the car has been driven aggressively (and sometimes even if it hasn’t). If you’re going to be tracking be aware that you will have to fix these things eventually, generally it is better to do so before they fail. We know what you’re thinking and yes, this chassis has issues. Luckily they’ve been discovered over the years and solutions have been developed for them so you are at least forewarned.

These two sets of reinforcement plates are preventative maintenance items which help to reinforce your front and rear strut towers against the common cracks and failures that occur with this chassis. Each is designed to distribute pressure more evenly onto the strut towers to prevent the mushrooming and cracking (see above) that is likely to occur when the car is driven aggressively (and sometimes even when it is not). These plates just help to give you peace of mind that your car will be able to handle the strain of being driven as it was intended. The rear plates are especially recommended if you are going to be running a “true coilover” in the back, which will be covered in our track suspension subsection.

Finally, a front strut tower brace might sound like more of a “performance” type thing but it actually plays an important role in chassis reinforcement. Because you are adding this big plate to the top of the strut towers and connecting them with a large rod, you are simultaneously strengthening them and redistributing pressure between the two towers. And hey, bonus, they look cool as hell!

-Weld-in Chassis reinforcement

These chassis reinforcement plates are a bit more difficult to install than the strut tower reinforcements as they require welding. However, if you are driving the E46 M3 aggressively they are essential for maintaining or repairing the integrity of your chassis.

The front subframe has to deal with a fair amount of stress during day to day driving due to the constant stress the motor is putting on them. As you accelerate or decelerate you engine will twist which puts strain on the mounting points for the subframe and the motor mounts. This is further aggravated by aggressive street and/or track driving, so generally it is best to address the issue with some front subframe reinforcement plates before it becomes a problem.

The E46 rear subframe is especially famous for its failures. When the subframe and differential bushings deteriorate it allows for a lot of flex of the subframe, which then leads to the sheet metal of the chassis being twisted and jolted under acceleration. A rear subframe reinforcement kit helps to strengthen the subframe and redistribute the twisting forces across a wider surface area. Replacing your differential and rear subframe bushings will help keep the problem from rapidly worsening, but it should be addressed ASAP for safety, especially if you are going to be tracking your car.

Another common area of failure when tracking the E46 M3 is the rear trailing arm mounting point. This RTA reinforcement kit strengthens the mounting point and distributes pressure more evenly along the mounting location much like the subframe reinforcement kit. These are a good idea to do at the same time as the subframe kit as they are in the same area. This would probably you money on labor as everything will be out of the way already.

If your rear strut towers are already experiencing cracking and light failure, rear shock tower repair plates can be used to fix the damage so you have a fresh surface to mount the rear shocks to. If you are running a true coilover in the rear you may want to install these even if your strut towers look ok just to ensure they can handle the pressure.

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