Put a koyo rad in it and it’s been good to go.
If you go aluminum Koyo is the way to go.
I went with Koyo. CARid was the best price at the time. Been 7 years and no issues.
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.
Personally I’d be buying a koyo in 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.
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.
It happened to me once at a night time. I just pulled over, stopped the engine and started again after several minutes and everything was OK.
Edit: After reading other's comments, I realized that mine also related to coolant system. Some time after this incident I replaced radiator because of a coolant leak. May be this warning is related to that.
My first non warranty repair on my B58 540 was a $3k radiator replacement. That was at about 60k miles.
You need to replace that. Bmws run hot. Only fix
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If choosing engine radiator across many manufacturers, check the part ranking. If your choice is down to two brands, the PartReview part comparisons help.
We compare engine radiator across these categories:
In March 2026 on PartReview, engine radiator Koyo were overall better than OEM BMW.
In March 2026 on PartReview, engine radiator Koyo were overall more popular than OEM BMW.
By vote balance, engine radiator Koyo surpassed OEM BMW:
By number of reviews, engine radiator Koyo surpassed OEM BMW:
In March 2026, according to PartReview, engine radiator Koyo led more car-specific ratings than OEM BMW:
Koyo are chosen by owners of cars such as: Honda S2000, and others.
Engine radiator OEM BMW have not yet taken leading positions in car-specific ratings. You can help by adding a review and specifying your car.
If this comparison didn’t fully answer your question, there are many others on PartReview.
For example, comparisons of engine radiator Koyo with: MISHIMOTO, Nissens, KOYORAD, Denso, OEM Volkswagen, VALEO, OEM Toyota.
Also available: comparisons of engine radiator OEM BMW with: MISHIMOTO, Nissens, KOYORAD, Denso, OEM Volkswagen, VALEO, OEM Toyota.
You can also see who is better among other engine radiator manufacturers: MISHIMOTO or Koyo, MISHIMOTO or Nissens, MISHIMOTO or KOYORAD, MISHIMOTO or Denso, MISHIMOTO or OEM Volkswagen.
