i have a 2004 outback 3.0 that started overheating 3 days after i purchased it. I had the obveous replaced; heat sensor. radiater cap. When I went to rewplace the thermostate I found that it had been removed. Put in an after market therm and it didn;t change situation. I replaced water pump. That didn't work. Situation now is that the two upper hoses get hot quickly and are under pressure; lower hose is much cooler and not pressureized.Logic dictates either a bad therm (but it overheated even when the therm was removed) or a bad radiator (but the radiator seemed to pass water freely when I had it out. I understand there is a chemical that detects carbon in cooling system. Seems that should be my next step to rule out hg. I also understand that heater plays a roll in cooling system but not sure how much it would effect water temp and pressure. Any suggestions would be appreciated

Asked by Mar 19, 2016 at 09:45 PM about the 2004 Subaru Outback H6-3.0 L.L. Bean Edition Wagon

Question type: Maintenance & Repair

started overheating. I replaced heat sensor, radiator cap. Went to replace
therm. but found it
didn't have one. Did relace it with a non subaru therm. Didn't solve problem
so replaced water pump. Also didn't solve problem. Current situation is that
the top two hoses heat up and pressurize very quickly while the bottom
stays cool and non pressurizes. At this point the engine is still cool to touch.  
I understand there is a hg problem with Subaru engines so I am getting the
chemical that will show if there is carbon in your cooling system. I also
understand that the heater core is a part of the cooling system. Don't know
if it would cause this problem. Radiator seems like a logical fix except I ran
water through it and it flowed smooth and clean. Any suggestions would be
greatly appreciated.

1 Answer


Subaru's, I understand, use a special oversized thermostat, so, using the aftermarket unit was probably a mistake. Cooling is a big part of the car, and I would not advise fooling around with this, otherwise, you could overheat and blow the head gaskets. That would be VERY expensive.

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