Originally Posted by letsteyr
hi gakusya, i think i got the same problem as you got.
A WRX STI 2006 2.5L + atp3071 turbo
Coolant overflows when i drive hard (i think it's more after driving hard)
No overheat, No consumption (oil or coolant), No milk, No smoke
A few little black things (2 or 3 in the bootle)
Tryed with a 1.3b upper cap => still overflow
changed my radiator with a koyo => a little less oveflow
changed the termostat with a crucial => still overflow
Coolant has difficulty to go back into the radiator except by very low temperature.
I did the carbon test (blue/yellow test) => No carbon, fresh air.
My compressions are balanced and ok.
My sparks are ok.
My coolant water is a common elf coolant water.
Can you give details about the coolant you put (brand, specs...). Thanks
It is genuine Honda coolant (I believe there is only one kind of coolant from Honda.). Plus, I added Subaru coolant conditioner. (So far, I didn't see any harmful precipitate or chemical reaction with Honda coolant.) Since I switched with Honda coolant, I have no longer have overflow problem.