AU JDM 91 legacy wagon EJ20T auto overheating

[tricktiki]

Hey guys im new to the forum and to subaru's i bought a jdm 91 legacy wagon and its been fine for last 2 months and now the weather has got more hotter the temp on the legacy has almost hit the red driving fast and slow.
Any help? And why im here what is the best oils all the way round the car engine, diffs, trans and coolant and how much of each?
thanks

[tricktiki]

Engine is stock still with Air to water intercooler. Just have pod filter and boost and turbo timer.

[Legacy777]

Welcome to the BBS.

Any chance you have any maintenance records on the car? How many miles (km) are on the car? Depending on the mileage I would suggest maybe replacing the thermostat and water pump. The thermostat needs to be a Subaru thermostat. Aftermarket thermostats from the auto parts store don't work right in these engines.

Have you verified that the radiator fans are coming on? You can plug in the green diagnostic connectors under the dash and the radiator fans will cycle on and off when the key is in the "ON" position. Some more info on the diagnostic connectors can be found on my site.

http://www.surrealmirage.com/subaru/engine.html

Also, when the temp starts to climb, if you turn on the heater does the gauge go down at all?

Does the engine run any differently when the temp climbs? Does the temp gauge climb immediately or take some time after driving around for a bit? There are actually two different coolant temp sensors, a 2-wire one for the ECU and a 1-wire sensor for the temp gauge. One may not be working properly.

As for oils, if you can afford it, run a synthetic in the motor. Mobil one is a good "lesser" expensive synthetic. The engine takes just under 5 US qts. Do you have a MT or AT? If MT, Subaru has their own gear oil called Xtra-S. I'd recommend running this in the transmission and rear diff. The MT & rear diff take just under 5 US qts. If you have an AT, any 80w-90 gear oil in the front diff is fine, and then Dextron III or higher ATF in the AT, and Xtra-S or another gear oil for the rear diff. The AT can take anywhere from 3-8 or 9 US qts, depending on how much is drained out. Pretty sure the front diff takes just under 1 US qt and the rear diff is just under 1 US qt.

[tricktiki]

thanks man sorted now problem was thermostat sticking and brown water. Now flushed an new thermostat new coolant.

[Legacy777]

Good deal! Thanks for the follow up.