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Discussion Starter · #1 · (Edited)
I know this has been covered a zillion times, but have some specifics and questions related to them. Hopefully will get a nugget of info and not the dreaded head gasket. The car is pretty nice all around.

  • Bone stock 2.0 WRX per my limited understanding looking the car over, Wheels, included.
  • Has 97K miles, one owner college professor.
  • Bought it from a dealer that sells donated vehicles (possibly the motivation for donating. lol), so didn't get service records.
  • Car looks well taken care of,. Original paint and pretty much damage free outside a few marks on bumpers, etc. Expected for driver
  • Car Has 152 to 154 PSI on all with compression tests
  • Pressure tested cooling system to 16PSI and things look good, no leaks
  • No oil in water, no water in oil, no milkshake under oil fill
  • Starts, makes no funny noises, sounds really good
  • Head gasket done at 87K miles according to the sticker on the engine
  • No obvious white exhaust, maybe a slight bit... don't think so tho.
Car will start and idle forever without issue. But take it driving and maybe 3-5 miles in temperature starts to rise quickly. I shut it down and coast, the car cools super quickly, and pop the clutch to start the engine to get off the road. I noticed the bottom radiator hose wasn't tight and pushed the coolant out the after the first time. I have been refilling with pretty much straight water till I have it figured out. Noticed that when it was getting hot, the heater quick working.
  • Will it flash boil if there in no coolant in the water?

I replaced the radiator cap with a Subaru Original since, burbed the cooling systems a few time with similar results. Have been using water to test it for immediate, but wondering if doesn't have enough coolant. I haven't been driving it hard or for extended distances but it's definitely feels healthy and smooth for stock. Know running without coolant is not a good thing but didn't want to the expense or make a mess with coolant till had it figured out.
  • Will the coolant flash boil and could that be a problem.

Next steps planned:
  • I have another OG Subaru thermostat going to install and retest
  • Will add proper level of coolant, burp, and retest
  • Will double check coolant flow after warms up. Is it possible water pump is just bad if water is circulating properly?
  • Will check coolant gases with blue carbon detection fluid. If it turns yellow, is that a pretty fail-safe indicator that the head gasket is the culprit?
Thanks for any suggestions. The 2.0 liter is supposedly not as prone to the HG failures, so I was holding out hope. Jumping to the head gasket it a pricey/time consuming effort till I've exhausted the rest of potentials.
 

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No Turbo EJ motor is prone to HG failures, that is a weird online myth that somehow got crossed over with the early phase-II 2.5L SOHC motors.

You should confirm that coolant is circulating. If it isn't, suspect thermostat failure. After a coolant flush, you will spend the better part of 2 hours burping the system. Patience is key here. There are a lot of coolant passages in an engine block and so a lot of places air can be trapped. Patience. Also, burp it some more.

I usually wouldn't expect water pump failure, BUT there is no mention of a timing/belt and water pump service in your original post. If that's truly the case, that is a GROSS oversight as the service will be 10 years overdue now. You should be on the third set of timing belt/tensioner/water pump by now anyway. First, suspect thermostat AND ALSO perform the timing belt and water pump service ASAP.

If the engine is overheating DO NOT DRIVE THE CAR. You will warp the heads causing irreparable damage.
 

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Discussion Starter · #3 ·
I didn't mention the water pump because I didn't have the original owners records as they donated the car. I can't imagine a good Subaru mechanic doing a timing belt on a 16 year old car and not doing a water belt and tensioners. I plan to do install a new thermostat and keep a watchful eye on the water pump for circulation issues. Thank you for the input Zax. Appreciated.
 

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So you do have records that the timing belt was replaced? When?
 

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Then I would suspect Thermostat failure.

Does radiator seem hot when the engine overheats?
 

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Discussion Starter · #7 ·
I have another factory thermostat to install... going to give that a shot momentarily.

Radiator seemed to be warm, but not hot based on what I could tell. Hard to check with the electric fans ready to fire at any moment and there isn't much room to get my hands in there. Will probably resort to using thermal gun to check temp of radiator.
 

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It's been a while since I've replaced my thermostat, so my memory is rusty. But is it possible the thermostat can be installed backwards? Also there's a air bleed that allows air bubbles to get out of the system. You'll notices it on the thermostat flange. It needs to be at the top.
 

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I haven’t done one in years but I could swear they only fit one way. Anyway if it’s the thermostat OP should be able to detect lack of circulation.
 
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