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1999 Legacy Outback, bone-stock.
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Will exhaust pressure from HG failure stop coolant from circulating?

1999 Legacy Outback, auto, power everything websites seem to indicate it has a EJ25D motor (not sure where to check on the vehicle), just bought under 2 months ago. Friend who sold it to me had timing belt & water pump done at time of sale (I thought the mechanic he used was a $&^*). I've gone 5k since, totaling 155K.

Last night within sight of my house, suddenly noticed cold air from heater. Looked at temp gauge and it was pinned to H. Pulled into driveway and shut down, opened hood. Radiator cap not especially hot, nor top rad. hose. Overflow bottle looked full but brownish in the flashlight beam. No cottage cheese on dipstick or oil filler.

This AM called in sick due to car, started to read up on the topic, HG seemed likely. Opened radiator on cold engine, added about a pint of water (figured no matter what, would be dumping it soon) until it was full. Started engine, hoping to see it puke out a burst hose or cracked radiator, no luck. Idled about 15 minutes with defroster on, temp gauge came up to middle but never saw flow in radiator neck. Burped a small bubble about once a minute. Got worried that if coolant wasn't circulating, temp in heads might be extreme, shut down engine.

Called friend in California who is Honda/Chevy "A" tech. He suggested maybe stuck thermostat. Called local Subaru dealer, talked to service desk. The guy there said that no cottage cheese in oil is normal Subaru HG fail mode, bubbles in coolant were sure sign of exhaust in coolant, and the part I found odd: He said that the exhaust pressure in the coolant was sufficient to prevent circulation???
 

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Will exhaust pressure from HG failure stop coolant from circulating?

1999 Legacy Outback, auto, power everything websites seem to indicate it has a EJ25D motor (not sure where to check on the vehicle), just bought under 2 months ago. Friend who sold it to me had timing belt & water pump done at time of sale (I thought the mechanic he used was a $&^*). I've gone 5k since, totaling 155K.

Last night within sight of my house, suddenly noticed cold air from heater. Looked at temp gauge and it was pinned to H. Pulled into driveway and shut down, opened hood. Radiator cap not especially hot, nor top rad. hose. Overflow bottle looked full but brownish in the flashlight beam. No cottage cheese on dipstick or oil filler.

This AM called in sick due to car, started to read up on the topic, HG seemed likely. Opened radiator on cold engine, added about a pint of water (figured no matter what, would be dumping it soon) until it was full. Started engine, hoping to see it puke out a burst hose or cracked radiator, no luck. Idled about 15 minutes with defroster on, temp gauge came up to middle but never saw flow in radiator neck. Burped a small bubble about once a minute. Got worried that if coolant wasn't circulating, temp in heads might be extreme, shut down engine.

Called friend in California who is Honda/Chevy "A" tech. He suggested maybe stuck thermostat. Called local Subaru dealer, talked to service desk. The guy there said that no cottage cheese in oil is normal Subaru HG fail mode, bubbles in coolant were sure sign of exhaust in coolant, and the part I found odd: He said that the exhaust pressure in the coolant was sufficient to prevent circulation???
Loss of coolant resulting in a pocket of air will stop coolant circulation in the system - YES-- your car is known for internal HG failures which case a simple test on the coolant after running the car with a HG test kit will let you know if the HG is toast. If the test is negative for exhaust gasses in the coolant then your issue is something else - failed tstat - leaky hose or some other blockage issue. OEM Tstats only!!! The cheap parts store ones are famous for causing over heats in subarus.
 

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1999 Legacy Outback, bone-stock.
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Discussion Starter #3
Interesting!

Dropping the tstat and checking for coolant circulation without it is within my resources of tools & time, head gasket job is not. Is it a waste of my time? Should I just get it towed to a shop? I deal with a good all-makes guy, but there is a Subaru specialist indie shop a few towns north of me in New Milford, CT.

You refer to "HG test kit," Do I need a Subaru specialist to check this, or can my local guy do a reasonably reliable test with non-Subaru tools?

And thanks for the warning on the OEM-only thermostats. I had read that in several threads, and was actually calling the local dealership to price the OEM part when I had the above-mentioned conversation w/ the svc mgr. I do appreciate the warning again.

THANKS!
 

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Pair O' Beans
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If you let the car idle up to temp, give the upper rad hose a squeeze. If it's rock hard, you've likely got cylinder pressure in the cooling system. This can hold the thermostat closed and prevent coolant from circulating.

If your car is overheating in normal use, it needs head gaskets 9 time out of ten. Don't try to work around it, don't wait. Everytime the car overheats makes it far worse.
 

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1999 Legacy Outback, bone-stock.
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Discussion Starter #5
Thanks for the info.

If anybody can recommend a good tech near Danbury CT or if there is somebody near here who might be willing to do the job for less than a shop, please chime in.

I am also considering the Japanese Domestic Market low-miles replacement engine option.
 
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