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Subraru Overheating

My son’s turn of the century Subaru Legacy Outback what overheating here in Spokane a month ago when it was in single digit temperatures for a few days. He put a couple of quarts of coolant in, which was a slow process. He put in a new thermostat suspecting a problem there. A couple of days later he was on the freeway and overheated again. He stopped and pulled off the radiator cap. There was a fountain of cold coolant. He suspected a blown head gasket. We have removed his engine and drained the oil. Oil looks good with no obvious coolant in it. He can blow through the radiator without a pressure buildup. The water pump bearings seem good. Before pulling the head and going through all that we are wondering if we are missing something. Any advice would be appreciated.

Are you sure the water pump is good? Is there flow? A leak down test on the cylinders would prove it.

If the car overheated and the radiator had cold coolant in it, than the coolant is not circulating. Unless he installed the T-stat backwards, than either the water pump has failed totally (I’ve never seen one fail totally) or there’s a blockage, perhaps a collapsed inner hose liner. This I HAVE seen. And since it was a “slow process” adding a couple of quarts of coolant, which should have taken less than a minute, I STRONGLY suspect a blockage.

Just because the water pump bearings seem good does not mean the impellars are not worn to a nub.

And I would not remove the heads until I did a pressure leakdown test on the cylinders. If you have no leakage, the headgaskets are not blown and removing the heads can only add to your problems.

Wow ! From over heating straight to pulling the engine. That’s ambition.

I am a little concerned by the phrase 'put a couple of quarts of coolant in it"

I know you don’t get a lot of really cold temps in Seattle and I wonder when, if ever, the strength of the coolant was checked.

If the radiator had ice in it , this could happen.

Thanks all. PvtPublic, he wanted to replace the clutch anyway.

Ah yes. New clutch and head gaskets. Shop would charge $$ to do that work. More than car is worth.