The 2015 Mustang is packed full of sleek design features that make it one of the slickest Mustang designs we’ve seen in a while. Ford really went after the details on this car, with every surface the driver touches being well thought out, and more of a personal and less of a corporate feel to the interior.

That’s why it’s so interesting to us, that when you open the hood on any 2015 Mustang it seems that Ford even looked at nearly every detail here. Every detail that is, except for the ’15 Mustang coolant reservoir or expansion tank. Given various nicknames throughout the Mustang community like “the blob,” “glob,” or even “grenade,” it just looks out of place on such a sleekly designed car. Fortunately for us, by the time the SEMA show rolled around Moroso had a solution. “Historically our company was one that was on the forefront of design and innovation and this product falls into that tradition. It used to be that when someone thought of Moroso they just thought that we offered Drag Race parts for Chevrolet products which we still proudly and always will, but today we offer products for Acura, BMW, Honda, Mini, Subaru, Toyota etc,” says Moroso’s Thor Schroeder.

Looking completely out of place under the hood on any S550 Mustang is the plastic coolant reservoir.


It was very important during the design and development process to ensure everything fit like oem. -Thor Schroeder

Building on its previous success with such products for the S197 Mustang, Moroso’s coolant expansion tank for the S550 is a high end part in both function and appearance. Constructed from aluminum and fully TIG welded, it’s also rugged and durable. Schroeder says that nearly any Mustang enthusiast, especially those of us who plan to push the limits of our cars can benefit from this reservoir. “Factory tanks fail after repeated high heat situations. Even the Mustang School cars that Ford has at Miller Motorsports Park all have aluminum coolant tanks on them.”

The reservoir accepts the stock cap, and all of the connection points are also TIG welded to the tank in the stock locations. Reservoir capacity is the same as stock, and the reservoir is shaped to fit under the stock hood. The mounting flange puts the tank in the stock location, with the factory hardware, and they even put the appropriate vent and spacer/stand on the tank body. “It was very important during the design and development process to ensure everything fit like OEM. We fit the prototypes of the tank on actual cars and made sure that the tank could replace the OEM tank seamlessly. We also went to the trouble of designing and producing a new to us billet aluminum neck for this tank that accepts the factory cap and has the built-in overflow provision like the factory neck,” says Schroeder.

The Moroso reservoir has built in provisions for all of the factory hoses. It even has a special billet neck to accept the stock reservoir cap and has an overflow provision just like stock.


Moroso sent us one for our Project 5-Liter Eater 2015 Mustang EcoBoost, part number 63806. It took us longer to write this article and snap the photos than it actually did to do the installation. Look for install time to take most owners 15 minutes, a testament to the attention to detail in this part’s design. The tools required are a pair of pliers for releasing the stock coolant hose clamps, a 10mm socket, short extension and ratchet. We also recommend having a couple of small buckets, jugs, or bottles handy to capture coolant as you disconnect hoses, and empty the reservoir. We cut apart a cleaned out 1-gallon milk jug, and used it.

These two bolts are all that hold the factor reservoir in place.

Left: With the bolts removed, we drained the stock reservoir into an open one gallon container. Center Left: The stock hoses are retained with these spring style clamps. Center Right: A pair of pliers or channel locks is all that's needed to loosen the clamps. Since our car had less than 1,000 miles on the clock, we decided to reuse the factory clamps. Right: After installing the Moroso coolant expansion tank we filled it using the coolant we'd captured during removal.

Installation Tips

  • Disconnect small upper hoses first. Use a small bottle on each to capture coolant that will leak out.
  • Have a couple of shop rags or towels handy to capture excess coolant.
  • Disconnect the mounting bolts second to loosen the reservoir.
  • Empty the reservoir into a container such as a cut open 1-gallon container or small bucket. Expect to capture about a 1/3-1/2-gallon of coolant.
  • Save your coolant, with a car this new, it’s no issue to reuse it as long as you captured it in clean containers.
  • After installation, start your car and bring it up to operating temperature, then check for leaks.

We have to say the end result is definitely better looking. We won’t be laughing with (or faking a laugh with) everyone who walks by when the hood is open and sees the original reservoir. Instead, we anticipate people asking us “Where’d you get that?”

Side by side, stock vs the new Moroso expansion tank.

Moroso offers this good looking coolant reservoir for all S550 Mustangs. This is just the start of its product offerings for the S550 platform, as the company is already working on or have available air/oil separators for the Mustang GT and EcoBoost, as well as a fuse panel cover and brake fluid reservoir cover for the S550 cars.