Jump to content

Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse

- - - - -

colder thermostat

  • Please log in to reply
6 replies to this topic

#1 Uberoo


    Subaru Wheeler

  • Members
  • 3,863 posts
  • lewiston,ID

Posted 22 July 2013 - 03:33 AM

The engine in my EA81 based off-roader is a phase 1 ej22 (90-94).Even though that engine is fairly reliable and bombproof I still have had several failures with it.The most recent failure was oil related-either the engine got starved of oil at high RPMs or the oil pump died.Anyway I am putting together a replacement engine and I was thinking I could address another potential failure point.As I mentioned before this engine goes in my offroader so it spends its time warming up and then getting submerged in water, then warming up,submerged,etc. Stock T-stat opens at 78*C/172.4*F and the engine currently runs 180-190, I am thinking a 160*F T-Stat would allow the engine to run at about 168-180*F so I am thinking a colder thermostat would help keep the engine just a little cooler and maybe lessen the thermal shock the engine goes through every time I go through a mud hole.I know a lower thermostat wont lower full load temps because a t-stat only sets the lower limit of operating temps and that if I am having a cooling problem a radiator cleaning might be in order.My problem is the engine is stuffed into an 81 hatch and I am already using a legacy radiator, space around the engine is a little tight and as a result it has always ran a little warmer than I would like so I am thinking a slightly cooler thermostat might help that a little bit.I know that when the engine is below operating temp it increases wear,uses more fuel,etc but engines in my offroader only seem to have a lifespan of about 1-1.5 years so anything I can do to extend that is welcome,because a year is a drop in the bucket for these engines under normal use but its an eternity in the offroader.

#2 Fairtax4me



  • Members
  • 13,034 posts
  • Charlottesburg, VA

Posted 22 July 2013 - 11:13 AM

Proper cooling system function is more important than a lower t-stat temp.
It's also very important to use the OE style thermostat since it is more able to handle quick temperature changes.

Proper running temp for these engines is about 200°, so even at 190 you're still below the normal temp for a road driven car.

Driving into water isn't going to bother the engine one bit as long as the bypass route of the cooling system is flowing properly.
The bypass comes from the water crossover, through the heater core(on a stock setup), then back to the water pump on the back side (spring side) of the thermostat. The bypass route is there to help keep the thermostat open in cold temperatures or if there is a sudden change in inflowing coolant temp. (Such as driving into water)
It does this by mixing hot coolant from the bypass with cooler coolant from the radiator right on top of the thermostat. This will allow for a gradual change in thermostat opening, rather than going from completely open to completely closed.
A benefit of using an OE style thermostat is that the larger mass of the OE stat holds heat longer and does not react as quickly to changes in coolant temp that may cause a cheap aftermarket stat to close and stay closed.

I'd stick wih the OE temp setting, and OE design. Just make sure that coolant bypass is connected and free flowing. (Heater core not plugged)

#3 1 Lucky Texan

1 Lucky Texan

    I read a lot about Subarus. '03H6OBW,'06WRX

  • Members
  • 7,987 posts
  • Texas

Posted 22 July 2013 - 01:29 PM

Mishimoto (and I think someone else?) makes a 'racing' t'stat that is cooler.


but I'm not convinced you'd nee it in your application. But you definitely don't want a cooler, aftermaket that ISN"T built with the larger wax capsule, if the t'stat housing was submerged, it might slam shut.


hmmm, have you considered some kind of wrap or insulation on the t'stat housing and lower radiator hose? Might help stabilize temps.

#4 Uberoo


    Subaru Wheeler

  • Members
  • 3,863 posts
  • lewiston,ID

Posted 22 July 2013 - 01:49 PM

even with the oem t-stat when it hits water the temp drops like a stone.

#5 WoodsWagon


    Formerly 91Loyale

  • Members
  • 4,102 posts
  • NH

Posted 23 July 2013 - 08:33 PM

Do you have the heater hooked up to it? Are you using a heater flow shutoff valve that limits circulation through the heater core?


The EJ needs full coolant flow through the heater core and back to the water pump housing all the time to correctly operate the thermostat. I used to have my EJ22 in a loyale with an EA82 radiator in water up to top of the wheel wells pretty often and never had any problems other than the automatic seat belts freaking out when they were wet.

#6 NorthWet


    Eeyore Incarnate

  • Members
  • 5,039 posts
  • Bremerton, WA

Posted 24 July 2013 - 01:10 AM

I would bet that the sudden lowering of engine temperatures is due to water on the engine surfaces in general, rapidly drawing off heat from the water jackets. 


These engines can dissipate a lot of heat from the engine just to the surrounding air... enough so that a radiator is hardly needed in cold weather.  Imagine what happens when water is sprayed all over it?

#7 Rooster2


    Subaru Master

  • Members
  • 4,728 posts
  • Indianapolis

Posted 24 July 2013 - 06:16 AM

If you simply want to run at a lower temperature, then run without a thermostat. It may not idle well when the motor is cold, but as an off road "mudder," who cares.

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users