173 votes
Had a Koyo on mine, it was perfect and kept the car cool year round in Southern California even in the canyons on 100+ degree days. It also handled track days without a hiccup
I just bought a koyo and it's a bit of a learning curve installing it. It took a few hours to burp the system of air but now I'm chasing small leaks. The OEM cap doesn't fit the radiator
I have a Koyo on my car and have no complains. I do tracks days and have never had any overheating issues.
The problem I'm running in to is that the upper hose connection is positioned differently on the Koyo N-Flow/dual pass(RH020539N) and it's really close to the Q45 throttle body and attached TPS. I've already cut off the unused socket on the TPS which gives me more room but still not a ton to work with.
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.
Roughly 12 months ago, I upgraded the radiator on my 2000 Series 8 (~65,000km/40,000mi) to a Koyo R1443N 48mm N-Flow. The coolant seals blew because the radiator's design allowed air to accumulate, creating hot-spots and leading to seal failure. My water temps never exceeded 90C. After a rebuild, a valve was installed on the radiator elbow, making it quicker to bleed the system, and water temps are now around 77C, about 10C cooler than before. The Koyo radiator's design prevented proper bleeding of the coolant system, causing seal failure.
Koyo is what I'm using. Quality stuff. I'd highly recommend.
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