Thanks for the tip - ZEREX G-05 - but i think y'all are nuts for not doing a chemical radiator and coolant system flush at least twice a year..... say on the first hot sunny day in Spring and on the last warm sunny day in Autumn - its an easy backyard chore and the Prestone flush kit lets you pressurize and backflush the sytem after nuking it with chemicals and then working with the engine stone cold. Gotta pull the thermostat too for best results and naturally wrap all electrics and disconnect the battery because flushing the system makes one helluva mess which in itself is fun. Can also be combined with cleaning the engine bay using whatever solvents you've got on the shelf.