Project E46 M3: Part 16 – Koyorad radiator installation

Project M3: Part 16 – Koyorad All Aluminum Radiator Installation

Cool Runnings

by Pablo Mazlumian

When it comes to our Project M3, most of its upgrades could be labeled as fairly mild, and with little compromises (if any). However, they’ve also shown that every little bit adds up enough to count. Compared to how this car started, Project E46 M3 puts out about 40 more wheel horsepower; stops more abruptly; handles better; sounds more menacing; and still keeps its original lines with a more aggressive appearance. These upgrades have also accounted for an 80-lb weight loss thus far, which enhances performance in all departments.

One of the departments we haven’t touched yet is engine cooling. For the most part, the car’s cooling system has been working well. Whether you’re cruising in traffic or doing some spirited driving, the water temperatures seem to stay between 185-200F.  The only time this car sees its water temp rise past the halfway mark is on a warm day while cruising at speeds under 30 MPH for several minutes, but only if the AC is on.

While turning the snowflake button off quickly encourages the needle to creep back to normal, I can only imagine what would happen in a real traffic jam. That said, it also seems I’ve come across several testimonials where taking an E46 M3 out on a hot track days tends to yield similar, overheating results after just a few laps.

To counter this problem, about a year ago Koyorad released its all-aluminum radiator for the E46 BMW M3, and we decided to install one today. This should not only eliminate any potential over-heating issues in the future, but it will also provide more consistent dyno testing since the temps will be far more stable. Also, as we all know, staying cooler usually means a little bit more horsepower in the end.

The timing is good for Project E46 M3 to receive its new radiator because of the factory plastic end tanks on the stock unit. Different car companies will advise to replace the radiator every 60k to 100k miles to avoid a failure of these plastic end tanks. This car only has 68k miles, but it’s also nearly 15 years old. An all-aluminum unit should last the life of the car.

I remember doing a test on a slightly larger intercooler in my previous E36 M3, and what I saw was consistently more wheel horsepower—about 4-5—when doing consecutive first-thru-fourth gear pulls.

Don't forget to check out Page 9–I posted a picture of a trailer home near the Kansas/Oklahoma border and its rather unusual cars parked in the lawn that I saw. I happened to catch them as I looked up from the computer screen while writing this very article from the passenger seat of our minivan.


When the new radiator arrived, we opened it up and it appeared well packaged from Koyorad. Packaging is crucial with all heat exchangers because you don’t want any of the fins to be bent.


The Koyorad radiator features the company’s HH Series high-density, two-row 48mm core, which promotes increased coolant volume, better air flow,  and improved circulation.

Koyorad's all-aluminum radiators are designed in Japan and either manufactured there or in Indonesia. This particular one for the E46 M3 is offered for an MSRP of $600, but you’ll find it online for about $400, which is only about $100 more than the price of a genuine BMW unit with plastic end tanks.


Here’s a shot of the backside, which will be facing the engine.

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