Put a koyo rad in it and it’s been good to go.
Pros: good to go
Reviews of Koyo engine radiator
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173 votes
Average rating
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If you go aluminum Koyo is the way to go.
Pros: good aluminum radiator
I went with Koyo. CARid was the best price at the time. Been 7 years and no issues.
Pros: no issues for years
Radiators aren\u2019t supposed to leak. I have the same Koyo radiator in my NA Z, just put it in this past summer. I def do not have that leak.
Cons: radiator shouldn't leak
Vehicle:
Nissan
Personally I’d be buying a koyo in full aluminum.
Pros: full aluminum
I went with a Koyo radiator, which is considerably better built than the factory piece, cost less than $300 with new hoses, and took maybe 2 hours, start to finish. Of course, I replaced the coolant at the same time.
Pros: better built than factory
Vehicle:
Honda S2000
just tested my new koyo hyper V at the track and that thing kept it rock solid cold, 180-203f the entire day but it was like 68 degrees out lol.
Pros: kept it rock solid cold
Koyo for top quality, mishimoto for normal quality. Both will do the job well
Pros: top quality
Cons: price higher than Mishimoto
I just bought a Koyo, goes in tomorrow and appears to be great quality
Pros: great quality
Seems like a loose ground, my s13 did this when the grounds randomly came loose. That said my s13 cluster is so damn slow to react so I run an aftermarket gauge. I have a koyo rad which came with a slot for an aftermarket sensor.
Also i would hope it's not the case, however you mentioned this after an alternator change. I had a 96 civic with a turbo setup and I had an alternator with a failed voltage regulator, all of my aftermarket gauges and temp gauge was acting like this. I would check the volts from the alternator if this is the case, it also ballooned the hell out of my battery..
Pros: aftermarket gauge reliable, alternator voltage check
Cons: potential voltage regulator failure
Vehicle:
Honda Civic
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What we know about Koyo engine radiator
The brand is registered in Japan. Official website: http://www.koyo.eu/.
In March 2026, PartReview users have a positive opinion of Koyo engine radiator.
PR Score — 92 out of 100, based on 57 reviews and 173 votes. 52 positive reviews, 2 neutral reviews, 3 negative reviews. Average rating — 4.4 (out of 5). Vote balance: 160 up, 13 down.
In the ranking of the best engine radiator this part is at position 1 ahead of KOYORAD and Nissens.
Users also evaluated the qualities of Koyo engine radiator:
- Overheating - engine runs hot in traffic or under load - rated positively. 4.5 points out of 5.
- Leaks - coolant drips or wet spots on the radiator or under the car - rated positively. 3.6 points out of 5.
- Sweet smell - sweet coolant odor from under the hood - rated positively. 5 points out of 5.
Engine radiator Koyo in car-specific ratings
See which car brands and models owners choose Koyo engine radiator for. Below are car-specific ratings where this part is in the Top-3:
- Koyo ranked #1 in engine radiator ratings for: Honda S2000 .
- Koyo ranked #3 for: Toyota 4runner .
Engine radiator Koyo in comparisons
There are 8 comparisons of Koyo engine radiator with other manufacturers on PartReview.
In particular, see which engine radiator are better: Koyo or OEM Toyota, VALEO or Koyo, Koyo or OEM Volkswagen, Koyo or OEM BMW, Koyo or Nissens .