I track my R53 and recently replaced the stock radiator with a Mishimoto Aluminum Performance Radiator. I hadn't had any overheating issues, I just thought it would be good to replace the 11 year old stock unit with something that was entirely aluminum and supposedly more efficient.

Yesterday it was 95 degrees f (35c) and my coolant temp peaked at 227f (107c). Since my mechanic said not to exceed 225, I would back off once things got this hot. A couple of things to note: the temp was not consistently 225, it would just bump up there at certain points on the track and was generally running a couple of degrees cooler. Also, it was a slow track with several hairpins, so not the normal amount of airflow one would get on a faster track.

I looked back at my telemetry from track days with the stock radiator and the Mishimoto, along air temps and humidity, and I can't say I see any improvement with the Mishimoto. Even though there are a lot of variables, one would think the 30% efficiency claim would stand out under the most demanding circumstances.

Here are some data points in F:

Radiator, air temp, avg. track coolant temp, peak coolant temp
stock, 89, 210, 216 (not driving as hard as I am now)
stock, 55, 203, 207
stock, 71, 203, 205
Mishi, 66, 203, 205
Mishi, 75, 219, 223
Mishi, 95, 223, 227

If anyone has similar data, I'd like to see it for comparison. Also welcomed would be any suggestions to improve cooling efficiency.

My R53 water temp runs between 200 & 220 irregardless of the outside temp. As soon as I take the checkered and begin the slow in lap it will drop to 190. This is measured at the front bleed hole with a AutoMeter water temp gauge.

225 is a little high - get rid of the AC condenser. Or add a front splitter.

when i drive around town in such weather, as im in constant stop and go and with high humidity, mine would go up to around 225-230 but then the fan would come on and reduce to 200-210. But driving on the highway (spirited driving) it would keep at 198-205. I'm running the a/c btw.
my car is 2005 - engine is stock.
[all temp quoted in fahrenheit]

For improving the cooling efficiency, maybe a new intercooler?

Maybe there is a little air in the system left to bleed out. Is it possible the car is purposely running hot for efficiency reasons if you are still on stock tune?

Your temps aren't out of wack---just keep an eye on it if it goes above 230.
I would check the system and give it a little bleeding just to check...seem odd that the temps jump from 66,203,205 to 75,219,223. Also check the fan to see that it's working properly especially the high circuit.

225-230 is not unusual at those ambient temps.

No..gen1 has a mechanical thermostat... Not adjustable unless you replace it...then many choose a cooler one...
Did you bleed it at BOTH BLEEDS?

I suspect so, but will double check with my mechanic.

Just curious, anyone know at what temp triggers the coolant warning light? Mine has never gone on.

FWIW, after running a 30 min. session at VIR in hot, humid conditions, my water temp will never go above 200F with oil temp at 240-245F. I concur that you may have an air lock. Are you using an Alum. recovery bottle with a higher pressure cap? I run distilled water with only about 10% coolant and WatterWetter.

Aluminum recovery bottle: Yes

How did you settle on a 10% coolant ratio?

Did you do any before and after tests with Waterwetter? The ones I've read have seen a much less than claimed decrease in temps.

Was just going to ask - running water? And some water wetter? There are different brands that do the same thing as water wetter also.

https://www.amsoil.com/shop/by-produ...code=RDCBCN-EA

Nothing worse than dumping your coolant on a track and "spinning in your own juices" or causing someone else to spin. I leave just enough coolant in there to give the system some protection from corrosion and to avoid freezing at the track in the Winter.

kyoo, thanks for the tip about the AMSOIL product. Looks like significant improvement over the REDLINE.

devenh, Thanks for the post. We would definitely suggest to re-bleed again to ensure all air has been evacuated from the system. If you would like us to look into this further for you, we would be happy to do so. Please feel free to contact us directly at support@mishimoto.com.

Thanks,
-Pat

All the tracks I've been to do not allow coolant (for this reason).