Engine radiator Koyo or Denso

I'd go with Koyo for price and ease of install. My reservoir hose nipple broke on my OEM radiator (OEM has plastic tanks) so I went with all aluminum for durability. My RX-8 also only drives on race tracks, so the extra cooling is nice.

I'd replace it with a fully aluminum one just because of that pesky plastic nipple that's prone to breaking. Koyo makes a good one.

I’ve had really good luck with Koyo radiators in the past as a really good replacement. The couple all aluminum radiators I’ve had, I really wasn’t impressed with the quality of construction.

I went Koyo. For me even with a stock engine its worth it not to have a plastic seam to worry about.

Go for a Koyo and never look back.

just replaced rad and all soft and hardlines with oem hoses and koyo rad. gives me a lot of reassurance in this LA heat. Great upgrade

The Koyo Rad needs it's own custom cap as the OEM won't fit but man does track city daily without issue and fits OEM fans it's a must have.

'07 V6 SR5 I replaced my leaking rad with a Denso four years ago and it's been absolutely rock solid. **NOTE** I'm not sure if this is still the case but some Denso rads have a couple little notches cut into the sides which are sometimes mistaken for damage as they are not neatly done (literally looks like someone just tapped it with a grinder). These notches are to allow the rad to expand a bit when the metal heats. They are necessary and part of the design even though they sure *look* like damage.

The previous owner had replaced it with a really cheap plastic tank one. It started leaking about a month after I got the car so I spent the money and got an all aluminum Koyo. Its a happy miata now.

I recently installed a Koyo radiator in my s13 to replace the stock one that had been leaking. I bled the air thoroughly when I filled the system with a spill free funnel and the bleed screw on the water outlet. Even after doing this, my car started overheating intermittently after driving around for a bit. When I stopped, the upper hose and radiator were very hot but the lower hose was cool to the touch. I tried to bleed more air out of it with the spill free funnel, but no air came out, and the water in the funnel started getting hot and overflowing. I pulled the thermostat to verify if it's functioning properly and it is, also it's the type that will stay open in the event of failure. This might seem silly, but I feel like the thermostat is closing and opening because the radiator is cooling too well.