Hi folks I have a issue with my wagon it is passing coolant from the radiator cap overflow. It has a large alloy mishimoto radiator dosent overheat and runs fine, I thought it might of been a weak spring in the cap so I replaced it the other thing I was thinking was maybe head gaskets?? Is this a common fault for subaru? ?

Not sure what you mean by "passing coolant". You should have an expansion tank which fills up when the engine is hot (as the coolant expands) then sucks the coolant back into the engine as it cools.

By passing coolant im meaning it's leaking past the rad cap and coming out the over flow. I have been topping up the expansion tank every few weeks

The overflow should run into the expansion tank.  The expansion tank should not be topped up, it should be almost empty when the engine is cold.  I think you may have been over filling the system.

Ok Adam that has mad some sense ill try that cheers