SOLVED - it was a I believe a small hole in the bottom right (facing engine bay) hose found when revving the engine when warm.
Replacing hose, thermostat and packing.
A year or more ago I had a parking accident and put a crack in the radiator of my GC8 WRX.
A Subaru guarage put a second hand radiator in my car for me.
*Since that time* I have had an intermittent leak of coolant only when the engine gets hot, after I have driven for about 30 minutes, or idling forquite a while.
The engine does not overheat
I have been pretty lax about replacing the coolant but even so no overheating
This makes me think that the coolant only leaks from the plastic reservoir and not the radiator itself
The coolant does not drip when I am not using the car.
There is no obvious crack in the plastic coolant reservoir or the tubes going from it to the radiator
When it leaks it spurts enough that steam rises from the right hand side of the engine compartment (the opposite side to the metal surge tank -so that is not it)
Just changed the oil and there appeared to be no evidence of coolant in there
We thought at first to replace the plastic coolant reservoir but now with the bumper off and the engine room there is no leak taking place and no green staining suggesting a crack.
The guarage I am at now suggested replacing the radiator cap and thermostat but I see no reason why the cap should malfunction immediately after the accident, and think that if the thermostat were faulty I would be having overheating problems.
Since there is no obvious leak, or green gunge, the mechanic thinks that perhaps for some reason coolant may be being blown out of the overflow pipe coming off the cap of the plastic coolant reserviour due to some sort of blow-back of pressure from the radiator (and not just when the coolant is overfull because the plastic reservoir empties). Has anyone heard of that?
The mechanic is letting the engine warm up now in the hope that we will be able to see the leak when it happens, but it does appear to be intermittent.
Has anyone had similar?
This post seems very similar but there was no recognised solution
This too but a solution was not posted
Disappearing antifreeze, maybe in the oil?
Everyone says "pressure" test but I don'T think that my mechanic even has a pressure tester
My ride is a 98 WRX Wagon of ozzie "Outback" type bought in Japan