Bad experience with a Subaru OEM thermostat

[mitch5]

I recently finished building a ej22 frankenmotor for my syncro and as part of the build decided to install a brand new OEM thermostat(82c) and OEM cast impeller water pump.

I tested the new tstat in boiling water to verify operation. Previous experiences makes this mandatory now.

Initial results were not great, i used a vacuum setup to fill the system but i was have issues with overheating at idle. Highway speed was fine but low rpm was not. This seemed to behave like trapped air so i rebleed the system and no luck.

I eventually decided that the old motor ran fine with my beck and Arnley brand tstat so this one should. Well upon changing them out i discovered the aftermarket thermostat had a substantially larger opening for coolant and that the valve had more room to open.

Switching them out yielding completely normal cooling operation. Every single subaru person will tell you to get the OEM thermostat, but now I am questioning that. It is my understanding that every single ej subaru uses the same 82c thermostat so why use a thermostat with a smaller potential opening for a cooling system that has to push coolant fairly far. I plan to buy another aftermarket tstat for back up and take some measurements.



Has anyone else had issues with the oem thermostat?

[DanHoug]

you didn't happen to buy the OE t stat on Amazon??! any markings to verify manufacturer? post a photo here, maybe someone with a genuine OE one can compare to make sure yours is also. so many fake parts out there.
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[syncrodoka]

We are talking about OE, from the dealer tstat? I have tested a few aftermarket ones and the didn't open as much as factory. I have never have issues with the dealer ones. Maybe thet have changed the design, time for pix

[16CVs]

Did the part come from Subaru in a Subaru box? It is then OE -- "Original equipment"

If it wer0e made by the OE vendor for Subaru and not in a Subaru box it is then (OEM) Original Equipment Manufacturer.

These terms are tossed about as they are the same, but the difference is as large as is the difference between a Carat Interior and a Weekender.

There I've covered 2 pet peeves in one thread.

Stacy
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[wesitarz]

Switching out the thermostats you did re-bleed it again. An easy way to bleed air out is to park it nose down and let it cool. Any air will collect in the expansion tank. Top it up and you're good to go. Position of the jiggle pin is said to be important - to the rear of vanagon with vertical thermostat and up with a horizontal thermostat housing. I've only had experience with one OE and one OE from the dealer.

[wesitarz]

The BA thermostat is 78 (172) opening and longer throw? compared to the OE 82 according to Rockauto info. I know my OE opened at about 180 as it would activate my inline temp sender going to the rad. Running temp was 190-200 (mean 195) in the PNW. What are your operating temps if you have an app for accurate readings?
Lower temp 78 degree/ longer throw might make sense with some conversions and type of coolant feedback to the thermostat.