I am trying to diagnose my overheating issue with my wagon.  I am trying to find out if there is a good way to tell what the problem is?  First I found a busted hose by the water pump,  replaced it, it ran for a day without issue.  Then it came back.  Then I did the thermostat replacement.  Then I found a small leak in a metal coolant line (near throttle) patched it with JB weld.  I thought that would fix the issue.  No deals.  I am trying to figure out the next step to find the problem.  Is it the water pump, radiator, head gasket?  Something else.  It does not blow white smoke.  The water pump does not make noise.  It does smoke a little under the hood near the throttle area.  Could it be that it is not circulating oil properly?  Could that be it?  Any ideas on how to definitively find the problem will be very helpful.  Block test next????  Thanks all.  

I am in the same place with you, no white smoke, fans work, new radiator, new thermostat...now looking at head gaskets for signs of leaks. Good luck to us both! Hoping not to have to pull it but not looking good!

at this point it is probably a combination of several things

 

1/ wrong t-stat. this should be subaru only.

the ones from the parts store are crap and will cause overheating.

if you still have the old one it is probly still good.

 

2/ you need fill the cooling system properly.

open the vent plug by the top rad hose,

and fill at rad cap SLOWLY.

when the coolant over flows the vent ,

plug it and top off.

idle engine until the t-stat opens

and then top off and seal the cap.

 

3/ burp the cooling system.

if there is air in the top of the system,

it will over heat.

it will likely idle all day long and stay cool,

but at speed it will overheat.

 

so if you are confident that you have fixed the leaks,

install and factory t-stat and refill the system correctly.

 

how to fill and burp your cooling system. - burpcoolingsystem - Subaru Legacy Forums

 

if there is a chance you may still have a leak,

i would fill it with plain water and test it.

if good, drain it and refill with 50/50 coolant

Edited May 30, 201411 yr by johnceggleston

I would not trust the JB weld fix.  

 

The IAC or Throttle body are easy to come by.  

 

Heck for $20 shipped I'd send you both.