Radiator dumping coolant into reservoir, overheating

2005 Subaru Forester, 175k miles. New radiator, thermostat, radiator cap, and water pump. Radiator is filling with air, reservoir flowing over with the coolant from the radiator, motor runs hot after about 20miles. What’s causing this and how do I fix it?

Take a look at your oil fill cap. If it looks like a chocolate shake was spilled on it you have a bad head gasket.

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Your Subaru has a blown head gasket.

Tester

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Go to your local Subaru dealer and get a bottle of cooling system conditioner. This works pretty good if the system isn’t too far gone, I suspect yours is but it isn’t very expensive so why not.

While you are there, get a quote for new head gaskets. The dealer techs are well versed on replacing these. Might get a new timing belt while you are at it along with any other parts recommended, I.e water pump, tensioner, oil seals etc. Cheaper to replace these while everything is apart.

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Agree with the others, Head gasket failure.

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Whose Idea was it to replace all those parts on an overheating Subaru with 175 thousand miles on it without first checking for a bad head gasket?

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Previous owner.

So, OP, how is car behaving, now?
I assume you bought it recently, did you sell it?

I received the car in a trade for some work I did with original owner’s horses. Vehicle still inoperable, but head gasket set should be delivered soon.

Did your friend tell you it was overheating? I assume so since it has new radiator. So, he said it wasn’t worth much, as is?