Car is running too cool, safe or not safe?
 

I currently have Mishimoto thermostat which opens up at 76 Celsius. I noticed that whenever I drive early in the morning or at night in the freeway which is much cooler than during the day, the check engine light would pop out (P0128) coolant temperature is below thermostat threshold. My coolant temperature was hovering around 70 to 72 Celsius when the check engine light appeared after 7+ miles of driving in the freeway. When I driving normally in town, my coolant temperature would hover around 76 and my check engine light would never appear when I drive around the city. When ever I enter the freeway, it takes about 1 to 2 minutes for my coolant temperature to drop to 70-72 Celsius. My current cooling mods are mishimoto radiator, their slim fan shroud and jdl oil cooler kit in preparation that I am going to turbo charge the car in a couple months. I flushed out my coolant and checked the thermostat whether it was stuck open but nothing was wrong with it. I am wondering if it is best to just leave the thermostat on or switch back to oem thermostat. What do you guys think?

So your car rarely works at CL state 2 and only at full throttle goes to 4.
This is one reason I choose Sard 82C thermostat that is only 6C below OEM plus that it's exactly same type/brand with the original thermostat, sorry but I don't trust Mishimoto.
Otherwise I think you won't have problems except increased fuel consumption while you can add some advance here and there, or at least this is my experience with my lower thermostat.

In my opinion, second only to the hoses, your thermostat is the most important thing in the cooling system. It would be the last thing I changed. For whatever reason, non oem thermostats seem to cause issues on any brand/make of car. I definitely understand wanting to help temps before they're an issue, but leave the thermostat as a last resort

In my case the thermostat I bought is same brand (https://www.ntcl.co.jp/en/), same series, same quality with the OEM and is used in other Subaru models so I don't think it will cause any troubles!

I had to replace my stock one I used stock again. I don’t think there’s a need to alter the temp

Could just go old school like we had to do when the fan was driven by a belt and didn't have all the fancy dancy sensors and auto on/off!


https://www.toyota-4runner.org/attac..._cardboard-jpg

But if there still IS fancy set of sensors & auto on/off stuff .. wouldn't it result in same temps, but simply longer or more frequent fan switch on cycles, due cooling off being slower due blocked rad area?

When you remap the car with the upgraded fan settings (lower start/stop points) actually the phenomenon you describe is much worse rather with the lower thermostat which mates better with the new limits, if you lower the fan limits you should also adopt thermostat limits which means a lower temp thermostat, am I wrong?

https://mobile.twitter.com/caterhamf...45724907036673

Go back to stock

That as well as if the ac compressor comes on due to defrost or you decide to flip the a/c on you've blocked airflow to the condenser as well because the fan cycle times are adaptive to when the a/c is on.

The modern technique is to edit the fan cycles in romraider or tuning in the software of your choice, it even takes into account vehicle speed. I set mine to turn on slightly earlier and to vent the engine bay at a stop. Temps are still perfect in the winter and used waynos values:

http://www.ft86club.com/forums/showp...4&postcount=34



Although I have had issues in the past with aftermarket thermostats, I believe in your cases if you're tuning your cars you should look into editing your fan curves to get the balance you guys need:
http://www.ft86club.com/forums/showp...4&postcount=34

It was a joke. The whole reference to the fancy sensors and auto controls was the actual answer. Why shove things in the rad when you can totally control when the fans come on and off? Guess it was too indirect a reference.

I'm ah feared you went too far back for some of the folks - :D


humfrz

Exactly what I say but if you lower the fan tables where they start to work by 5C degrees it is better to change also thermostat open point by the same amount by changing it:

OEM thermostat opens at 88C, fully open at ~95C
OEM fan tables: 95C on - 91.5C off

In my case
NTC thermostat opens at 82C, fully open at ~89
NTC fan tables: 90C on - 87.5C off

In my case the lower thermostat helped me by reducing flkc as coolant lowers intake temperatures.