Thermostat MISHIMOTO or AISIN

Hard to say if it’s directly OE to Subaru, but I use Aisin thermostats and water pumps on every Subaru engine I do, they function the exact same and are equally as reliable as the original equipment, not to mention these thermostats are $15 on amazon compared to $40 from Subaru.

It’s now got an 85°c Mishimoto thermostat. Took it out today and got it up to temp and did multiple 0-85mph pulls. The new thermostat opens at 85°C/185°F. Under load the coolant never registered above 197°F!!!!

Mishimoto has a great thermostat plus it has a lifetime warranty

I spent a good chunk of change on the Mishimoto thermostat and it got stuck closed within a couple months. Needed the car back right away and all I could get was a dirt cheap MotorRad one. Darn thing has been it in now without issue for a good long while now.

New thermostat (Aisin brand), fresh oil, fresh coolant, replaced at that time. Coolant system bled well. No leaks. Heat worked flawlessly. AC worked after the swap. Overheated the drive home after that swap, turns out the radiator fan module got fried on the final drive (it was above 250 on coolant temps before replacing the engine, on a 30 minute, fast, highway drive). Ordered a new one. Everything working perfect now at the right temperature points. Engine times reading perfect too (watching live data). On a 30 minute highway drive tonight, returning home after the same drive 2 days ago with zero issues, it overheats again. Radiator fans are working. The one thing I changed during the drive was turning down the heat from HIGH to 75. No more than 10 minutes later I hear the bubbling in the heater core area. Take my exit from the highway, and the red temp light starts flashing, temps read 239, and the bubbling worsened. Temps stayed above 228 until I made it home from my exit. Worse at red lights. Turned off for 10 minutes, turned back on, temps went up to 232 at idle, holding steady. Lower radiator hose read 102 degrees, upper hose reads 190.

Get that mishimoto garbage out of there and put a new oem thermostat in there. Unless you really lile pulling the engine out, to replace coolant seals and rusted rotors...

please remove the mishimoto thermostat they fail a lot, it happened to me as well.

Même souci sur 350Z

Le thermostat Mishimoto s'ouvre à 82° au lieu de 68°/ la réponse du constructeur → du moment ou la température reste stable !!!!!!!!!

Je suis énormément déçu de cette réponse surtout au prix et frais de douanes que cela comporte.

Aisin THF-003 thermostat was used (I believe this is what I'm regretting). It's like the thermostat isn't opening? Everything else seems fine - it's clearly getting hot. Little to no heat at idle. No circulation = overheating of the engine. Is the replacement thermostat stuck shut?

Forget about the Mishimoto thermostat. The OEM thermostat is way more reliable and does the job.