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Old 08-26-2019, 02:53 AM   #2 (permalink)
Stubby79
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Join Date: Sep 2012
Location: Victoria, BC
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Firefly EV - '98 Pontiac Firefly EV
90 day: 107.65 mpg (US)

Little Boy Blue - '05 Toyota Echo
90 day: 33.35 mpg (US)

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Confirm that it's the head gasket (there's a couple of different methods) and replace it if it is...
And check that your water pump is flowing properly...I've heard of plastic impellers disintegrating. If it isn't pumping worth a dang, it's just going to overheat again and kill your head gasket.
Running lean can cause overheating as well, which might mean it's related to your P0420 code, and all your other efforts might not fix the underlying problem.
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