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: $306.00

Sale Price: $265.00

FinishAdd Cap?



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

Reg. Price: $306.00

Sale Price: $265.00

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

Purchased immediately after my NC overheated, and almost badly. I noticed my temp went up to high real quickly as I was about to get off the highway for my exit, I was able to make it home and into my driveway just as it started to boil over and spray coolant into my engine bay. My dealership played around with the car for a few hours and couldn't find the exact issue. They replaced a few hoses but it would still overheat under their supervision. I had a guess what caused the problem after reading up on this website, so I had them replace the OEM plastic tank with this Moroso tank and they replaced the thermostat since they thought that also could of been the culprit as well. I highly recommend all NC owners replace their plastic tanks with this ASAP. I was very fortunate and didn't do any engine damage, but many NC owners find out there is an issue when it is too late. I went with the aluminum finish since it was the cheapest and I needed it fast. Shipping was less than a week and my dealership said installation was a breeze. Although I have a new thermostat I do notice combined with this tank I run slightly cooler than before. So if you are replacing your tank, have them do the thermostat while they are there. My NC is a garaged, 'summer only' fun car with less than 67k miles. I would have been devastated if my engine got destroyed due to a cheap, plastic tank. This has been the only issue I have ever ran into while owning an NC Miata of something failing, so for everyone out there thinking about buying one, they are extremely reliable except for the factory coolant tank.

Peace of mind is priceless, but for less than three hundred bucks, there is no better way to resolve a potential cooling problem. The Moroso thanks is beautifully welded, and it is a great addition to your engine bay. I went with the plain aluminium look, as you can perfectly see the fat welds, and the nice polished finish. This is a must for any NC owner.

The tank is well built and almost a piece of art. Install was simple and quick. Looks great in my engine bay and now I don't have to worry about my tank cracking- ever. Thanks Good- Win!!!

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 !

The welds on this tank are art. Very happy with it, very easy install.

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

Excellent build quality. Installation took 15-20 minutes. I would recommend siphoning out the coolant from the factory expansion tank prior to removal, it makes much less of a mess.

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


First of all thank you for the information about the plastic tanks and the possible defect and consequences. It was on the bases of this information that I decided to purchase your aluminum replacement tank.

So, in my humble opinion, the tank is very well built and very easy to install. Everything lined up perfectly. It definitely looks great! It definitely instills confidence.

If I were to comment on one issue it would be the larger fitting on the bottom of the tank. It seems to be a little larger than necessary as it was somewhat difficult to get the hose over it.

Besides that I enjoyed the installation process and am very happy will it and would recommend it to anyone who is thinking about purchasing one.

Best Regards,

Steve Raven

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