Mazda Rx8 Koyo Radiator Installation

After breaking off a nipple on my stock radiator, it’s clearly time for an upgrade. After some research it seems that a 2 pass Koyo Radiator should be great, though I was a little apprehensive because of all the comments about it not cooling correctly at idle. Well, it does. In fact, I’m pretty sure a lot of these comments are related to the gap that surrounds the fan shrouds which need to be filled in for it to actually pull air through the radiator instead of simply going around it. I live in Las Vegas and the Rx8 Koyo radiator allows me to sit in traffic in 110 degree weather with the A/C working and my Rx8 does not overheat.

Sorry about the picture quality, I replaced my camera soon after this after seeing just how bad the pictures came out.

Now for some pictures!

  • Thanathan Einar

    Nice, how was the fitment?

    • Fitment is great. The only real problem is the gap that I mentioned in that “quick blurb”. Basically there is a 1/4″ air gap all the way around the radiator before it meets the fans. Fill this with foam and everything will be good. I don’t remember the exact date I bought the radiator and hoses but I know it was well before this was posted so over a year now.

      • Thanathan Einar

        Thanks for your reply!
        Nice to hear that the fitment was great, I was looking for Information about the fitment and found many other examples where the Fitment was terrible, many say it fits 100%. Damn you internet! πŸ˜€

        The gap around the radiator seems to be normal with aftermarket radiators.

        So, thanks again πŸ˜‰

        Greetings from germany

        • Funny you mention that. After I installed it, I was actually mad at the internet. I almost went with the Mishimoto because of some of the things I was reading online about the Koyo. In the end, I’m glad I didn’t listen to the threads on rx8club regarding fitment. Its a great forum overall but the desire for some of the more vocal members that OEM everything is perfect gets a little old.