hey
welcome to the boards
real bummer on ur engine.. know how you feel... been thru a few things like this too
check to make sure that your clutch fan is working properly... while the car is off spin the fan clockwise... if it turns real easy and does say a full revolution without any resistance i suggest you get another cupling for the fan.. also if the fan has a bit of play in it could also mean the cupling is going
what degree thermostat have you got in it?
what went wrong with the piston?
did you get a toyota head gasket?
what was the head gasket torqued to?
when the car was first run was the heater put on full blat till it warmed up?
does the dash gurgle when you start the car?
is your radiator blocked.. have you had it flushed by a radiator company?
did the mechanic take your engine block & head to the reconditioner and get them both prepped for a new head gasket?
it is very important that both surfaces been absolutely clean and also check that your head is not warped
it is very likely that if your engine had gone to a engine shop they would have found a crack in your block so i think it is safe to assume that your mechanic didn't do this (which they should have)
when we rebuild engines we send the head and block to the reconditioner every time without fail
also it is a good idea to replace your water pump at the same time
does the water bubble out the overflow bottle?
how do you know it is overheating? what are the symptoms?
well there's a start for you... let me know all of these and i shall continue