As some of you know we have been using a Koyo aluminum radiator for the past couple months. We’ve now put 6,000 miles on the car, ran a couple atuoX events and now has a track day with this radiator.  We absolutely love it! The car performed awesome over this past weekend at Auto Club Speedway in Fontana, CA.  Temperatures were over 105 and the temp didn’t go up at all. We did 4 sessions at 20 minutes at a time. A lot of you have asked how was the install on it and can it be done at home. It absolutely can be done at home with regular tools. We put together a install guide in case you needed some help installing the Koyo Radiator. Visit for more info



Koyo Radiator replacement guide for 2006-2015 Mazda Miata

In this article, we will be detailing the process to install your brand new Koyo radiator into your 2006-2015 Mazda Miata. This install was done on a 2014 Miata Club Edition, but everything in the engine bay as far as the cooling system will remain the same between the years. From this point on, we will refer to the car by its chassis code: NC.

This install is fairly complex, as you have to remove basically everything from the battery forwards. It is highly recommended, that if you want to upgrade your headlights to a retrofitted system (or add HID bulbs), change your intake to a cold air system, update your front bumper, upgrade fans, etc. do it all at the same time. This is suggested because many components that you would need to remove for the installation of the above mentioned parts, are removed during this time for example: intake, splash guards, battery, radiator, fans.
Tools Required:

  • 10mm socket and ratchet
  • 10mm wrench
  • Various extensions
  • Flat head screw driver
  • Pliers (various sizes helps)
  • 12mm socket
  • Coolant
  • Phillips screwdriver

Time allotment
Please allow for approximately 6-8 hours to do this installation. This isn’t your typical radiator swap. The packaging of this car does not allow for an easy install. Also, it would be best to have a friend help you on some steps.





This installation was performed at the Garage Star HQ in Sacramento, CA on the Garage Star NC3 Club Edition.  We used a lift to perform this install, however it can be done on jack stands.  When using a lift, jack stands, power tools etc, please take the proper safety precautions. Please dispose of your coolant and oil in the proper manner.



NOTE: This install is best done when the car is cooled down. No one likes to work on a hot car, and no one likes hot coolant in their faces. This is a long install, grab some drinks, food, listen to music but most importantly – take your time, and be patient.

Step 1:


Jack up the car: Take extra precautions when jacking up your car to ensure it will not slip off the stands.


Step 2:



Begin to remove the splash shields. There are a total of 3- 2 in the wheel well and one under the engine. The front of the splash guard is held in by phillips head screws, and the rest of the paneling is held in by fasteners which can be removed using a flat head screwdriver. The rear and wheel wells do have 10mm bolts holding them in.




You will need a 10mm socket and extension to reach this 10mm bolt holding in the wheel well splash guards.

Step 3:



The drain bolt is located in the front of the radiator, drivers side. It can be taken out with a phillips head screw driver, take caution to not strip this drain plug.




Place something under the drain plug to catch the coolant coming out. Once you position your pan, you can remove the radiator cap to help coolant drain quicker.  




  • Never open the radiator cap if the car has just been on, the system is pressurized and can cause harm to you or others.
  • Dispose of all coolant in the proper manner determined by your city, county or state.

Step 4:



The fun begins now. Remove the coolant hose from the top of the battery cover, as well as the battery cover.


Please Note:

Being organized now, will save you hassle in the long run.



Remove the bolts holding in the intake box.  There is one phillips head/10mm bolt on the intake arm (green arrow), and 2 bolts on the intake box holding it to the chassis (blue arrow). Use a flat head screwdriver to unclip the MAF sensor.

Remove the air box, and filter.




Here you will want to use a flat head screwdriver to remove the plug for the MAF sensor.





This fastener for the bottom of the air box is a bit tricky. If you are standing at the front of the car, pull it towards you. It’s a rubber grommet that holds it secure. It may be stuck and will take some persuasion to get it to release. Don’t spray a lubricant on it to coax it free, your ecu is below.



This is what it looks like once removed.

Step 6:


Next we will remove the water reservoir. There are 3 coolant hoses connected to it as well as a few 10mm nuts . Use a pair of pliers to remove the hose clamps and if necessary, grip the hose with the clamps and wiggle the hose free.






Step 7:


Undo the battery, remove the tie downs, negative and positive wires. Once the battery is removed, remove the 10mm bolts holding the tray in. You will want to also remove the bolt holding down the power steering reservoir.




Step 8:



Now lets remove the ecu. There are 4 bolts holding in the ecu cover. Remove those.




Press the clip down (blue arrow) and then swing the white arm back and you will have the cable disconnected. Remove the ecu and black paneling under it.



Unplug the fan, and separate the coolant hoses from the fan shroud.



Step 10:



We will now remove the AC and PS components which attach themselves to the radiator. Remember –  take your time, you don’t want to damage your PS or AC lines. You may want a friend to help hold parts up while they dangle.
The AC condenser and lines attach at the front and sides of the radiator and can easily be removed using 10mm wrenches and ratchets.



The upper radiator stays are this l shaped bracket. 2 10mm nuts hold them in. Then remove the lower radiator stays, those are held in by 12mm bolts.

Step 11:




Now its time to install your Koyo Radiator in. We put the radiator in without mounting the fan first.

Transfer the rubber feet from the OEM radiator to the Koyo radiator, and reattach mounting points and AC lines. You will need a friend to help.  




Koyo uses the OEM rubber mountings for the lower radiator stay.




Take your time when reinstalling your AC components.



Now you’re ready to install the fan. Simply slide it back into place, Koyo’s radiator has areas for the stock fan mounting brackets.  


Step 12:

Simply follow these instructions in reverse to reinstall everything, battery, air box, ecu etc. You can then begin to bleed the coolant.


Step 13:

Enjoy your new Koyo Radiator!