<< the stuff came in this morning, i did buy the ventable radiator cap for 6 bux at advance auto, and put in a new subaru t-stat as well for 13 bux. i put the stuff in, ran it for an hour with the rad cap vent open as it says, shut the car off, closed the vent and it is currently cooling down in the driveway. >>
how are you bleeding the system of air when you replaced the thermostat?
i opened the vent plug on the right side of the radiator, took off the top hose and filled that first (also put the "steel seal" in there too) reinstalled the hose, filled the radiator, and let it run for a few b4 capping it and letting it run for the hour it called for.
HOWEVER the stuff didnt work, as we all expected it wouldnt. but i am now driving the car with the lever on the radiator cap up, and so far so good. it releases the gasses that come in from the bad HG, without pushing the coolant into the overflow tank. atleast so far... i even got on the highway with it for 2 exits cruising about 75, checked when i got home, and tank still isnt filling up.
so that may be an inexpensive option for one of these with a bad HG and you want to continue driving it. buy the STANT radiator cap with the red lever on it (6.59 at advance auto) i bought the 13lb cap, they had 13 or 16lb caps. put it on, leave the lever up, but make sure the up part of the lever is aiming towards the firewall and it will clear the hood when you shut the hood. if you have it facing towards the front bumper, i think the hood will close the lever when it shuts. i will def update this if it changes, or overheats again, but as of now, im going to run it as is and see what happens.