Second Koyo Radiator leaking...
 

Hey Guys,

So this will be the second Koyo radiator I've gone through. This time it's leaking from bottom seam toward the rubber stops that go into rad support. First one I installed myself and bled thoroughly. This second one I had it installed professionally. I just recently tested the radiator with a cooling system pressure tester and was able to see where the leak was coming from. I sent footage to Koyorad in attempts to have it warrantied, but they declined it saying it was past 1 year warranty. Anyone else share the same pain with Koyo radiators? I was going to go with a different brand, but I'm having a hard time finding something comparable for track use. Any advice or suggestions are appreciated. Thanks!

Many will not agree, but I have always tracked Mishimoto radiators in my previous cars. I have only had two that have developed leaks. One of them I do not count because it was an "OEM replacement" radiator for the Z and was plastic. I have since upgraded to a double row aluminum model for the Z and, although I have not tracked it yet, it is still holding up well to Florida heat after 3 years. The aluminum radiator that I ran in my previous car had developed the leak after 3 years. Mishimoto still replaced it under their lifetime warranty.

I'm glad you're holding out well with the Mishimoto. Well, at least Mishimoto has that lifetime warranty if things go south which is never the case with Koyo. I'm curious to hear if anyone has had any issues with their Koyos. Anyone know what makes the Mishimoto and Koyo so different?

Bumpity bump bump bump

Patience.... it is a holiday

I've always thought highly of Koyo, cold day in hell when I put a mishi on my car (sorry 818)

what thermostat and radiator cap are you using?

It dawns on me that people are awfully brand specific with radiators ... I've always used C&R Racing - they dont make a true OEM replacement but that's never stopped me.

is the radiator getting enough airflow so it can do it's job? Maybe post up some pictures?

Yes, this is true. Most of us are already in food comas if we didn't start drinking in the morning from the get go. Duly noted.

I currently have the 38mm hyper v 2 core Koyo downflow radiator with OEM thermostat. The cap is the Koyorad 127kpa(18 ish psi) cap. I saw some of your posts but thought it would be too much of a hassle to fabricate. I already had to dremel the crap out of my mishi fan shroud to get the Koyo to fit. Although, I just took a look and they actually have a 350z specific rad:

https://www.crracing.com/product/nis...3-06-42mm-core

That looks promising but wow the price though. It's about 700 buckaroos. I only have the AC condenser in front of it. The power steering cooler is off to the side so it shouldn't affect it much. There's plenty of space in between rad fans and engine. I did see a thread about keeping your undershroud intact which I don't. I have a feeling that this may have contributed to the issue of not enough air flow during spirited drives. :( I don't think I have a head gasket lift because I didn't see any milky sludge in oil from coolant and no smoke out the exhaust. Motor mounts seem to be fine since I don't hear any abnormal sounds in the front of the car. The rad support is firmly in place.

The C&R looks promising. What's your experience with them thus far? I have some videos of the coolant leak that I'll post a bit later.

Yea - I'm not suggesting you fabricate to fit a universal in. I didnt realize C&R made a OEM equivalent - my universal was $200 - I dont know if I could pull the trigger on a $700 radiator.

are your ECT staying in-range while your running the car hard?

I've had a good experience with C&R (but at a $700 price point it would be out of my range)

To be honest, I only monitor the water temps when I have my surface plugged into my ECU. It all checks out but then again, I may not be catching any fluctuations of temps when not plugged into it or monitoring it. The oil temps seem to be fine though according to OEM on board temperature gauge.

Here's a link to the vid:

Strange, maybe just bad luck? Mines going on 2 years with no issues. High pressure cap and installed it myself. Where did you buy them from?

Dragon - has any welding or fabrication been done on the radiator?

I picked up an eBay Mishi replica "Speed Daddy" for 112.56 shipped in 5/2018. It's been great so far. But I use the OEM cap. Higher pressure than normal is going to test any weak points.