NC Aluminum Coolant Expansion Tank, Moroso 63779 for MX5
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Images may differ from actual product appearance.

NC Aluminum Coolant Expansion Tank, Moroso 63779


PART NUMBER: 61-2037


Reg. Price: $299.00

Sale Price: $243.90

FinishAdd Cap?



Free shipping offers apply only to destinations within US Lower 48.

Reg. Price: $299.00

Sale Price: $243.90

FinishAdd Cap?



Free shipping offers apply only to destinations within US Lower 48.


Forever fix the risk of your NC motor overheating because of a stock expansion tank failure. The NC is the ONLY generation of Miata where the overflow is a pressurized critical part of the cooling system and when the original plastic version fails you can have the motor quickly destroyed with overheating, often before the driver has a chance to notice the temp gauge spiking upwards. This all metal tank prevents that potentially very expensive failure.


9/2020 Update: Our Coolant Expansion Tank is now endorsed by Mazda Motorsports as a recommended part of the cooling system upgrades for all Spec MX-5 Race Cars!


Direct replacement for your factory plastic coolant expansion tank. Made in the USA, all aluminum with beautiful TIG welding. Constructed with internal baffles and a machined aluminum neck that takes a factory cap. All of the inlets and outlets are positioned to match up with the factory hoses. The tank mounts to the same location as the factory tank and is built with the same dimensions for an easy fit. Includes view window on the side to check coolant level.

Option is to add a high performance CSF 20 psi radiator cap. These tanks are compatible with the factory cap, so replacing the cap is not mandatory, but if you need a replacement for your used factory cap then this is the best option, and higher pressure than the factory 16 psi cap!! A true high performance cap to match your high performance expansion tank.

NEW optional satin black powdercoated finish offers a more subtle option than the bare aluminum. The satin black is a low-gloss finish that looks right at home in the NC engine bay, unlike a wrinkle or high gloss black that matches nothing around it. Some other examples of powdercoated tanks done by individuals or other shops make the mistake of coating the nipples where hoses and cap attach. That is a no-no! This premium powdercoating is done at the factory the correct way with all critical areas properly masked so that you get a great looking finish without compromises.

Stock plastic tanks are ticking time bombs because as they age they crack and when they crack the coolant pressure is lost and the motor overheats. Unlike the earlier Miata where an overflow leak was not big deal, the NC relies on this tank to be a pressurized part of the cooling system, as soon as a crack forms pressure loss causes the engine to overheat and the motor is usually destroyed. We have NC Generation Miata arriving on flatbed tow trucks every week with blown motors because the owner didn't change the plastic tank until too late. So we decided it was time for a "lifetime" solution. This tank is the solution. It will not fail over time like the factory tank, and looks great as well!

Installation NOTES:
CLAMPS: While the factory squeeze-clamps on the hoses can be re-used, they get weaker the more they are removed/installed and having a tight seal on all the hoses is important since this tank is pressurized. We recommend changing the squeeze clamps out for worm drive hose clamps which can be found at any auto parts store. #4 worm clamp (x2) for the top two nipples, #10 worm clamp (x1) for the bottom.
CAP: You might need to very slightly adjust the 'tangs' on the factory radiator cap to fit the new metal neck with same tension as it did on the factory softer plastic neck, takes a few seconds to do with pair of needle nose pliers.

Great write-up of the install process over on the Revlimiter blog:

YES, there is a view window on the side so you can see coolant level, see it in that window and you are good to go!



Optional satin black powdercoated finish!



Customer Reviews

NC Aluminum Coolant Expansion Tank, Moroso 63779

Just pony up and get this Moroso expansion tank. I got the CX Racing and it fits like a red-headed step child! Had to bend the shit out of it, then it stripped the mounting screws, then had to buy new nuts.

Really well made tank. Fit perfectly. I got the black powder coated tank, and it looks great with all the other black trim in the engine bay.

Beautiful upgrade! Easy installation. Now I don't lose sleep over a possible tank failure. Go with the bare aluminum finish - you won't be disappointed. Add the CSF cap for extra protection and bling. I wish I could post a pic to show how striking this tank looks in the engine compartment.

Great quality product. Easy to install. Took maybe 15 minutes. Peace of mind !

Timely processing and shipping. Quality workmanship and easy installation following the video provided. Peace of mind at last. Couldn't be happier.

Very nice item. Great welds on the entire unit.
fast shipping well packed
Almost looks factory

I'm new to the Miata world so I was very grateful that I learned about this tank cracking issue with the stock coolant tanks. My Miata only has 40k miles and the tank still looked very good with very light discoloring but even had this tank been white and looking perfect I'd have still replaced it just for peace of mind. The tank arrived within a week to ten days or so at the most and it only took 30 minutes to install it. Most of that time was to pull the fluid out of the old tank. I emailed asking them about exactly which new clamps I'd need and they gave me an answer within a half hour. I didn't even have to burp the system. Just filled up the fluid to show on the glass window and it was good to go. I advise just buying a cap for it too rather than try to save a few bucks. Just get it. This will likely be in the top five of the smartest purchases for this car.

I originally bought a plastic replacement tank after I heard about the failure issue with the tanks. Mine was original. Then I found this sweet Aluminum tank by Moroso designed in cooperation with Good-Win-Racing. For less than three times the cost of the plastic tank I had this tank of a tank! It was easy to install with basic tools and really looks sharp too.

After reading about the ticking time bomb, aka the OEM plastic coolant expansion tank, lurking under the hood of my NC I decided to perform some preventive maintenance.

After a brief search of various Miata forums it became obvious that the aluminum Moroso replacement unit was the obvious choice

The tank arrived quickly and I was pleasantly surprised by the high build quality. The tank is made from aluminum and quite hefty.

Installation was simple and well documented.

The Moroso unit is significantly more expensive than the plastic OEM tank. But apparently the OEM tank is doomed from the outset due to a material problem that causes it to deteriorate and fail unexpectedly. When you consider that the failure of the plastic tank can destroy an engine, the Moroso suddenly looks like a bargain...

I just skimmed all the laudatory reviews on this expansion tank. It's everything everyone says it is. You won't be sorry. Sometimes good-win shipping charges annoy me. But I'm learning. Good stuff shows up fast. Just do it. In the case of this product, you can rest easier afterwards.

High quality, easy to install, looks great. Purchased my car in October, it's a 2013 with 20k miles. Nervous about the old age of the plastic, and wanted to replace it with something better, especially as this tank is pressurized (why replace with a part that's going to go bad eventually? if you have the money for this, it's a good one stop option).

Thanks Goodwin!

My cooling system failed twice, once leaving me stranded on the side of the highway. The first time replacing the cap seemed to fix it. But then shortly afterward the plastic coolant reservoir neck melted right below where the cap screws on. For me the upgrade to an aluminum tank was a no-brainer. I also went ahead and changed the coolant while I was at it.

Installation was straightforward with no problems or surprises. I reused my factory hose clamps, but for some reason my cap just wouldn't fit, so I had to replace it.

In my opinion this purchase is a good investment, even considering the notable price premium over a plastic replacement tank. I don't expect any problems with this tank for the remaining life of the car.

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