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Functional Form – Expansion Tank R&D, Part 1: Stock Review

Modern society tends to view vanity as an unwanted trait. But, without a certain level of vanity, our lives would be dull, to say the least. People care about how something looks, whether we put a value on that appearance or not. We use our eyes to recognize danger and make critical decisions about our lives. The weight we naturally apply to our vision affects less important decisions, too. We choose our clothing, our food, our homes, largely based on how they look. If it weren’t for our natural vanity, nobody would care about Lamborghinis or Ferraris. We’d all drive brown Camrys, wearing brown shirts and brown pants on our way to our brown houses.

We surround ourselves with things that we like to look at, and those things say something about us, which is why the great divide between form and function in the automotive community has always been confusing to me. On one hand, there are enthusiasts who are obsessed with function and only function. It doesn’t matter how it looks as long as it works. On the other hand, there are those who only care about form. They don’t care that 10 degrees of wheel camber kills traction and wears tires in half a mile; it looks good (or something).


Whether either side wants to admit it or not, these two ideals often bleed together. To survive as a manufacturer of automotive parts, a business must cater to both groups. Hammering on beautiful lug nuts is not acceptable to even the most aesthetically focused customer, and a high-flowing exhaust with caked-on welds is not appealing to anyone.

For most manufacturers, the visual focus is on the exterior of the vehicle and passenger compartment. After all, most owners will spend 99% of their time looking at those two areas. When it comes to under-the-hood aesthetics, car makers often fall into the function-over-form camp. They throw a plastic cover over the engine, but pumps and tanks take on any form that gets the job done. A perfect example of this can be found under the hood of the latest generation Ford F-150 EcoBoost. Behind the aggressively styled grille of the 2015+ F-150, you’ll find something a little less thoughtfully designed.


The expansion tank of the 2015+ F-150 EcoBoost emphasizes function over form, but it falls short in some of that function. The tank is constructed of clear plastic that allows you to see exactly how much coolant is in the tank. Vertical supports inside the tank and domed areas across each support provide more strength and act as baffles to keep coolant from sloshing around when turning or over uneven terrain.

While the plastic construction keeps costs down and is useful for seeing when the coolant is low, the clear material becomes a yellowish color over time. As that happens, it becomes difficult to distinguish the coolant line. There’s another flaw inherent to the plastic construction aside from discoloration. Constant heat cycling (around 350*F for 12-15 minutes or until golden) deteriorates the plastic, eventually causing cracks and leaks. Anybody who’s ever broken an old plastic clip in an engine bay knows just how brittle plastic can become.


Aside from its functional flaws, the 2015+ EcoBoost expansion tank has a more obvious flaw. In Ford’s quest to make a more functional expansion tank, they inadvertently placed a bag of dinner rolls front and center in the engine bay. Add in the eventual yellowing of the plastic and this expansion tank ends up looking like it would be oddly delicious with a slice of butter. Even for somebody who’s not concerned with aesthetics under the hood, this tank can be a pretty big eyesore. The contrast of the translucent white plastic with the deep, black engine bay makes the tank pop out as soon as you open the hood. For anybody who’s paid the money to keep their Race Red, Lightning Blue or any other color F-150 clean and polished on the outside, this expansion tank can make popping the hood a bit of a letdown.

While it’s great that Ford thought about the end user with a clear expansion tank and ensured it functioned well from day to day, the 2015+ F-150 EcoBoost expansion tank still leaves a lot to be desired; or it leaves you wanting a buttery roll while you’re trying to change your oil. It’s our task now to take the functionality that Ford spent so much time perfecting and make it beautiful.

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