Gourmet Muscle – Oil Cooler R&D, Part 1 – Stock Review and Design Plans

The muscle car is a simple recipe written by Detroit in the 1960s. Start with one heaping cup of fire-breathing power plant. Add two rear wheels slinging the power to the road and a manual transmission to taste, then garnish with a sleek, sexy shell. Simple, yet effective. Like any simple recipe, though, someone always comes along with the artisan take. The result is essentially the same, but with a waft of complexity and pretension, much like the E6X M5 and M6. 

BMW isn’t the first thing that comes to mind when discussing muscle cars, but the formula fits. One screaming 5.0L V10 at the front, power sent to the rear wheels, and one big grin gleaming through the tire smoke. Like their American cousins, the Deutsche Braun Bimmers need adequate cooling to perform their best. Specifically, they need to keep all 9.8 quarts of engine oil at the proper temperature. 

BMW’s engineers were also keen on this need and included an oil cooler from the factory. This cooler wouldn’t break a sweat keeping the S85’s oil at operating temperature in its heyday, but the oil cooler did not age as well as the rest of the car and needs to be addressed. First, though, we need to take a closer look at the stock system.

It’s well-known that oil works best when it stays in the system, but the cooler on these Bimmers have started having trouble with that task. Of course, the apparent risk is road debris piercing the lightweight tube-and-fin core, but that’s actually not the primary source of leaking when it comes to the E6X oil cooler. 

BMW’s design allows for a single pass flow while retaining mounting simplicity. To achieve this, their engineers, in essence, split the hardlines at the cooler. So, under closer inspection, you can see that there’s still about an inch or two of oil line from the bracket to the hot-side end tank. After hundreds or even thousands of heating cycles, combined with vibrations and chassis flex, these line extensions are known to crack and leak oil. 

When it comes to our plans for the muscle M’s, we have two main objectives, with the obvious priority being durability. To achieve this, we plan on starting from the ground up with a full-aluminum construction, including a much sturdier hard line connection. Instead of leaving the lines exposed to the elements and vibrations, our new mount will be a solid block of CNC-machined aluminum, mitigating any risk of cracked oil lines. 

The second prong of our plan is unlocking more cooling power from this system. We plan to expand our core dimensions for improved surface area, combined with a bar-and-plate construction for vastly improved heat dissipation with the added benefit of enhanced strength. 

Another key component of the muscle car formula is dependability. With an oil cooler that’s prone to leaking, the E6X M5s and M6s start to push themselves out of the category. However, with some work, these Bimmers can continue their gourmet muscle car status. So, make sure to stay tuned for a first look at how our plans come to life.

Thanks for Reading!

-Nick

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