Best Miata Radiators: Performance Upgrades & Cheap Replacements

The radiator is a key component of your car’s cooling system. What it does is simple, yet vital. Your engine produces heat; the coolant absorbs this heat, passes through the radiator tubes where it cools down and gets circulated back to the engine.

This is, of course, an oversimplification of how it actually works, but you get the idea.

When maintained properly, a radiator should last for over 10 years. We’ve even seen great examples where radiators have lasted for a car’s lifetime!

If you drive an NA or NB Miata, we strongly recommend that you get your radiator checked if you haven’t because as of today, these cars are between 15 and 25 years old and most of their stock parts are going to need replacement.

In this guide, we’ll explore some of the best radiators for your Mazda Miata MX-5.

Whether you are seeking an upgrade or simply needing to replace a failed radiator with a similar unit, you’ll find the info you’re looking for right here.

Symptoms Of A Failing Radiator

The cooling system on early Miatas is known for poor airflow and coolant path. It is important that your radiator is in good condition at all times, otherwise, you may end up with an overheated engine, at risk of doing more major damage.

You don’t need to be a professional technician to spot a bad radiator. Some of the most common telltale signs of a failing radiator include:

• Endtank discoloration (turns greenish-brown)
• Leaking coolant
• Overheating engine
• Depleting coolant level
• Sludge in the radiator
• Water pump failure
• Thermostat failure

Miata MX-5 Radiator: Upgrade or Replacement?

If your current radiator is failing and you simply want to replace it with a new unit similar to stock, then OEM style radiators are your best option.

They’re fairly inexpensive compared to full aluminum, performance radiators which are designed to surpass the stock unit’s cooling efficiency in order to aid any performance modifications you may have made.

OEM radiators are usually seen with a thinner, single row design and plastic end tanks. If your Miata’s engine is absolutely stock and you maintain your cooling system well, it should last for years.

On the other hand, upgraded performance radiators are specifically designed to take on the additional heat produced by the modified engine and commonly feature a two-row, full aluminum design.

There’s no harm in using a performance radiator on a stock car; except that it can cost more. But if you’ve got a turbo or a supercharger, then a performance radiator is highly recommended.

Performance Radiators: Things To Consider

Radiators designed for upgrading your Miata’s cooling system are built very differently and are more complex than the regular OEM replacement ones.

Dimensions

A tall, wide and thin radiator that has good frontal surface area is the ideal design to go for, as it enables the best possible heat dissipation. If the radiator is too thick, it will build heat within itself, defeating its own purpose.

Fin Density

Fins are wave-like metal structures that form a mesh, spanning across the front surface of the radiator and their primary function is to direct the airflow.

Fin density, as the term suggests, refers to how dense the fin mesh is. While higher fin density enables better cooling, it can also restrict airflow and put more pressure on the fan at idling RPM.

Passes

Most automotive radiators come with a single pass design where the coolant flows in from one side, flows through the passages and exits out the other side.

However, some radiators have additional pathways that recirculate the coolant within the radiator, allowing it to make more than one ‘pass’.

The more passes a radiator has, the more circulation the coolant receives, leaving it exposed to the cool air for a longer duration.

The only downside of a dual-pass or triple-pass design is restriction of coolant flow. This, in turn, increases the operating pressure of your system, meaning you’ll have to pump a higher pressure to move the coolant.

Rows

Internal rows are pathways for the coolant to flow through. With rows, there’s always a trade-off between rigidity and heat transfer. Single row radiators are better at dissipating heat whereas the dual row ones are stronger.

You will also come across 3 and 4-row radiators but it’s best to avoid those. In order to fit more rows, the width of the tube needs to be compromised; and on top of that, the additional ‘gap’ between the tubes adds to the obstruction of heat transfer.

The greater the width of a radiator tube, the more coolant can come into contact with it, resulting in better heat transfer. Fewer rows equal better heat transfer but more power demands more rigidity and hence, more rows.

Material

Theoretically, copper and brass are much better at dissipating heat but since aluminum is stronger, it allows manufacturers to make radiators with thinner conducting tubes and fewer rows. This is why aluminum is the most preferred material for performance radiator designs.

OEM replacement radiators have an aluminum core with plastic end tanks. While plastic is light, it is a poor conductor of heat. Though end tanks don’t really participate in the heat rejection process, the material they’re made of still makes a difference. Most OEM style replacement radiators come with plastic end tanks as they’re easier and cheaper to manufacture.

The Best Miata Radiator Upgrades

Stock Miatas don’t have the best cooling capability, to begin with. The airflow is inefficient and the engine is known to overheat even in regular driving situations like prolonged high speed runs with the a/c running.

That said, it’s clear that a cooling system upgrade is much needed, especially if you plan on making modifications to improve your car’s performance as it will inevitably generate more heat.

For Miatas with turbo/supercharged engines, built for any kind of motorsport will require a cooling system that’s a lot more superior than OEM, and getting a full aluminum, high-performance radiator is the first step in that direction.

If you’re looking for the best Miata radiator upgrade, these are some of the best ones you can buy:

Koyorad

The ‘Koyo’ name dates back to the 50s when it started as a radiator repair shop in Japan. Today, they’re among the major suppliers of aftermarket and OEM cooling equipment. The Koyorad company collectively has over 50 years of experience manufacturing cooling system equipment, specifically. They supply OEM equipment to many car manufacturers.

All their radiators are brazed with Nocolok flux which is a great indicator of good quality. This brazing process ensures longevity and resistance to corrosion.

Koyorad’s ‘Hyper-V’ line of radiators for the Miata MX-5 is designed with space-saving in mind. The tubes and fins on these radiators are dense enough to increase the cooling surface area while still allowing adequate air circulation.  This two-row, high-density design is very effective for motorsport applications.

Unlike other brands, Koyo radiators are available across all Miata generations.

Fits: 1989-1997 | NA | Mk1

Part Number: VH060245
Core Size: 25.5 x 12.5 in.
Weight: 7.8 lb
Number of Rows: 2
Core Thickness: 36 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 18 Months
Buy From: Amazon

Fits: 1999-2005 | NB | Mk2

Part Number: VH060650
Core Size: 25.5 x 12.5 in.
Weight: 7.5 lb
Number of Rows: 2
Core Thickness: 36mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 18 Months
Buy From: Amazon

Fits: 2006-2015 | NC | Mk3

Part Number: VH061885
Core Size: 22 x 16.5 in.
Weight: 8.0 lb
Number of Rows: 2
Core Thickness: 36mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 18 Months
Buy From: Enjuku Racing

Note: Minor adjustment of condenser mounts may be needed due to the air conditioning being installed at the port of entry.

Fits: 2016-2018 | ND | Mk4

Part Number: KH063152
Core Size: 16 x 21.5 in.
Weight: 8.5 lb
Number of Rows: 2
Core Thickness: 25 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 18 Months
Buy From: Enjuku Racing

Mishimoto

Mishimoto began operations in 2003 with a focus on manufacturing performance cooling parts for track cars, daily drivers, trucks, and motorcycles. They soon became a favorite in the tuner community and are now among the most sought after brands, when it comes to aftermarket radiators.

Mishimoto radiators for the Miata MX-5 feature a magnetic end tank that filters out unwanted metal bits from the coolant and a 1.3 bar, high-pressure cap that allows a higher boiling point, making the system safer and more efficient.

Its two-row, 50mm core, full aluminum design is ideal for Miatas that see street and track use and the unit does a fantastic job at keeping the engine cool even at prolonged high speed runs. Only the one for 1989-1997 Miatas features a 3-row design instead of two.

As a reference; when using this radiator, the coolant’s temperature in a stock Miata, at moderate speeds, will see a 10-degree drop if compared with regular, OEM radiators.

Quality control is the only downside to these radiators as it’s not uncommon for them to have minor defects (like a bent fin), though these can be easily rectified.

Fits: 1989-1997 | NA | Mk1

Part Number: MMRAD-MIA-90X
Core Size: 12.6 x 25.12 in.
Weight: 15.8 lb
Number of Rows: 3
Core Thickness: 50 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: Lifetime
Buy From: Amazon | Enjuku Racing

Fits: 1989-1997 | NA | Mk1

Part Number: MMRAD-MIA-90
Core Size: 12.59 x 25.11 in.
Weight: 20.5 lb
Number of Rows: 2
Core Thickness: 50 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: Lifetime
Buy From: Amazon | Enjuku Racing

Fits: 1999-2005 | NB | Mk2

Part Number: MMRAD-MIA-99
Core Size: 12.80 x 22.17 in.
Weight: 20 lb
Number of Rows: 2
Core Thickness: 50 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: Lifetime
Buy From: Amazon | Enjuku Racing

OPL

Based in the USA, OPL offers a 10-year warranty on their parts and they’re also a part of the Specialty Equipment Manufacturers’ Association (SEMA) which is a large group representing the aftermarket parts industry in the USA.

It took us a while to decide whether OPL radiators make a better replacement, or upgrade, as they are priced very reasonably. Their dimensions and quality match that of more expensive performance radiators like those from Mishimoto or Koyo and many buyers have claimed that the results too are almost as good.

OPL radiators feature the same full aluminum design as seen on higher-end radiators and the manufacturer claims a 30% improvement in cooling efficiency. Experience wise, there is definitely an improvement over stock radiators but it’s not good enough for track use especially on hot days.

We recommend using more powerful fans with this radiator it tends to not work as well at low speed as it does on moderate and high speeds. This may be due to a higher fin density and restrictive airflow.

Fits: 1989-1997 | NA | Mk1

Part Number: HPR160
Core Size: 25.25 x 12.5 in.
Weight: 10.45 lb
Number of Rows: 2
Core Thickness: 50.8 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 10 Years
Buy From: Amazon

Fits: 1999-2005 | NB | Mk2

Part Number: HPR163
Core Size: 25.25 x 12.5 in.
Weight: 10.26 lb
Number of Rows: 2
Core Thickness: 50.8 mm
Core Material: Aluminium
End Tank Material: Aluminium
Warranty: 3 Years
Buy From: Amazon

Cheap Miata Radiator Replacements

Due to the mechanical simplicity of radiators, there’s only so much that manufacturers can do to differentiate their products from one another.

While looking for radiators online, you will notice that a lot of them look similar, but are sold under different names. You will also come across many unbranded radiators which in many cases, aren’t all that bad!

These OEM replacement radiators provide sufficient cooling and are a great option if you intend on keeping your Miata MX-5, stock. If you’re looking for a durable yet cheap Miata radiator, these are your best options:

TYC

TYC is the most talked-about OEM replacement radiator brand, especially for the Miata MX-5. Their radiators are almost identical to what the Miata originally comes fitted with. Featuring a single row aluminum core design with plastic end tanks, it holds up reasonably under normal driving conditions.

A little known secret is that TYC repackages the radiators manufactured by Koyo. Which is why, when you order a TYC radiator online, you may receive it in a Koyorad box.

TYC radiators fit right in and don’t require any additional work. The fitment procedure is straightforward, and you can easily do it by yourself with a few good tools.

Fits: 1989-1997 | NA | Mk1

Part Number: 1140
Core Size: 25.3 x 12.6 In.
Weight: 10.89 lb
Number of Rows: 1
Core Thickness: 25.4 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Fits: 1999-2005 | NB | Mk2

Part Number: 2268
Core Size: 25.5 x 12.62 in.
Weight: 7.56 lb
Number of Rows: 1
Core Thickness: 25.4 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Denso

Denso radiators go the extra mile when compared to TYC, owing to superior fin waves that allow better airflow and heat transfer. These are slightly more expensive than other OEM replacement radiators, but the quality is certain.

Just like TYC, Denso radiators are also a direct OEM fit and do not require any additional work.

Fits: 1989-1997 | NA | Mk1

Part Number: 221-3502
Core Size: 25.5 x 12.62 in.
Weight: 9.39 lb
Number of Rows: 1
Core Thickness: 25.4 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Fits: 1999-2005 | NB | Mk2

Part Number: 221-3505
Core Size: 25.31 x 12.62 in.
Weight: 9.39 lb
Number of Rows: 1
Core Thickness: 15.24 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Fits: 2006-2015 | NC | Mk3

Part Number: 221-3515
Core Size: 21.62 x 16.8 in.
Weight: 11.77 lb
Number of Rows: 1
Core Thickness: 15.24 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Spectra

From a brand presence point of view, Spectra premium is more appealing than other OEM brands. All Spectra products are designed and engineered in North America.

Their radiators are thermally tested under real temperature simulation, feature a high tensile aluminum core, and specially formulated rubber compounds that make sure it withstands the harshest weather conditions.

When you order Spectra radiators online, the chances of receiving a damaged item are far less because the packaging is durable and transit-tested. Additionally, you will also have access to their very own customer support.

Fits: 1989-1997 | NA | Mk1

Part Number: CU1140
Core Size: 25.12 x 12.6 in.
Weight: 9.7 lb
Number of Rows: 1
Core Thickness: 31.75 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Fits: 1999-2005 | NB | Mk2

Part Number: CU2268
Core Size: 25.5 x 12.6 in.
Weight: 7.05 lb
Number of Rows: 1
Core Thickness: 15.74 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Fits: 2006-2015 | NC | Mk3

Part Number: CU2861
Core Size: 16.5 x 21.5 in.
Weight: 10.65 lb
Number of Rows: 1
Core Thickness: 15.74 mm
Core Material: Aluminium
End Tank Material: Plastic
Warranty: 1 Year
Buy From: Amazon

Our Favourite Miata Radiators

There’s no doubt that every product mentioned in this guide is worth buying. Which one you should get, and for what purpose, are the only questions that remain.

Best Miata Radiator Upgrade

Though the lifetime warranty by Mishimoto is tempting, we recommend the aluminum radiators by Koyorad.

Koyo is among the top OEM suppliers and so, we’re sure they know a thing or two about designing reliable radiators. The brand has been around for decades and is very well reputed in the market.

Best Replacement Miata Radiator

This one’s a no brainer. We’d recommend TYC as the best replacement radiator. If you’re looking for a cheap Miata radiator that is equivalent to what your car originally shipped with, look no further than TYC.

Another reason for recommending TYC is that they’re manufactured by Koyo!

Feature image: more power, adaptation by Low Offset, original by Robert Couse-Baker, CC BY 2.0