BMW E46 M3: Expert advice on buying, modding and more

Rennie Bryant

Redline Bimmer Performance
redlinebimmer.com

First, check for signs of abuse—and not just the kind from a young driver or a lot of track use. Lack of maintenance is a killer, too. Get service records if you can.

Rear suspension mounting points ripping out of the car is more common than you might think. Rear trailing arm bushings and lower control arm bushings should also be inspected. The good news is that performance upgrades are available for cheaper than stock, and they will improve handling, too.

The VANOS variable valve timing unit can be another source of expensive problems. This unit is located on the front of the cylinder head. Listen closely for odd knocks and rattles from this area. There are many aftermarket upgrade repair kits and mods available to eliminate this problem once and for all. 

If you’re looking at a convertible, make sure the top works well going up and down. This car has a hydraulic top, meaning it has a pump and many rams that operate by means of oil under pressure. Yes, they fail. And yes, the aftermarket comes to the rescue with less expensive, longer-lasting parts.

Oil leaks, power steering leaks and coolant leaks are typical problems. Oil leaks most commonly come from the valve cover gasket or oil filter housing gasket, although sometimes the oil pan gasket is the source. As for power steering leaks, believe it or not, the low pressure hoses leak—on all BMWs. If you see a coolant leak, it’s most likely coming from the radiator expansion tank, the radiator itself, or sometimes the water pump.

Don’t be too scared by the list above. Many cars have already had these issues fixed, so records are important. Always get a pre-purchase inspection done by a BMW shop. It could be the best investment you make. Even if the car flunks the inspection, it will save you thousands.

Once you have a car and want to start improving it, suspension and engine tuning are the place to start. Then, install bigger brakes, lose some weight, and add sticky tires, headers, and a supercharger or turbo. The possibilities are endless.

The most popular suspension upgrades are bushings, and there are many options available. Heavy-duty rubber, urethane and solid replacements are the three main choices. 

There are also coil-over kits if you want to get more serious. Bilstein, Koni, K&W offer quality options. Tuner kits from Turner, BimmerWorld and Ground Control are also some good products. To add more adjustability, camber plates and adjustable rear lower control arms are
good additions.

A good cold-air intake will add some power, but don’t waste your money on a cheap version. A heat fence is a must, as hot air from under the hood will cost you power. 

Next, a new ECU is a good idea. It’s not really cheap, but it will definitely give you more power and torque while raising the redline and removing that pesky speed limiter. 

Exhausts are a matter of personal preference. There are many good systems to choose from offered by Remus, MagnaFlow and Borla. Most create gains within 2 or 3 horsepower of one another, so you can pick the sound you like best and go with it.

Drew Ingram

Turner Motorsports
turnermotorsport.com

Maintenance records, especially dealer work, are extremely important. This engine and chassis kept BMW busy through the years with rod bearing recalls, VANOS and valvetrain weak spots, software updates, and chassis failures—and at least one class-action lawsuit. I would also want to know about the previous owners: if they tracked the car, if they used aftermarket or OE parts on it, where they had it serviced, and so on.

The best suspension upgrade for you depends on what complaints you want to address. We like to take a concentrated approach to what the customer wants. We have everything, but just blurting out “Bilstein Clubsport” is not what every customer wants to hear. 

The most common complaint about the factory setup is the lack of front grip leading to understeer. We typically address that with wider front wheels and more negative camber. A front anti-roll bar upgrade also does a lot, especially for street driving. For a track car, the hot kit that we have now is the aforementioned Bilstein Clubsport—unbelievable features and performance.

When looking for more power, the first step is to add a set of headers and delete the cats. However, with the cats in the dumpster, the car won’t pass emissions testing. If you have a track-only car, then headers and a standalone ECU are the way to go. We have a Bosch Motorsport plug-in ECU with impressive gains and complete tunability. 

But the best upgrades with no downsides are gearing and differential upgrades. Gearing makes a huge difference because this engine doesn’t make a lot of torque, so getting into the powerband sooner is key. The most popular are still 3.91 or 4.10 ratios. Most E46 M3 diffs need a rebuild by 60,000 miles anyway.

We do a subframe repair and reinforcement on customer cars at least once a week here. That involves all of the rear suspension bushings and mounts. 

This car is quickly replacing the E36 M3 as the fun weekend or track day toy. I think people were initially afraid of them—engine failures and recalls didn’t help—but as time went by there was less and less to be wary of. Today, there’s not much that hasn’t been figured out. 

But I always warn people that just because the cars are becoming cheap, that doesn’t mean they need less maintenance or cheaper servicing. They are going to be very pricey for some owners who don’t realize what they’re getting into. Do it right, not cheap.