Need some help, 1989 Supra Turbo just became undrivable.

[mc_p0pe]

So, last friday i was about to go on a trip. I changed my oil and filled up my transmission fluid while my car was idling in neutral, lean i might add. Just as a pour the last bit of fluid it needs into it i hear a hissing and from under the engine steam starts rolling up. Naturally i can smell that it is antifreeze and my heart drops... i turn off the car and it continues pouring from the bottom, running down the transmission until the pressure in the system goes down. So, i cant see where it is coming from... somewhere under the engine on the knock sensor side. i jacked up the car to get a better look from the bottom, but the leaking stopped and nothing was to be seen. So, i filled up what coolant was lost started it up and waited... after about 30 seconds the pressure must have been back and coolant was pouring out again... this time i was under the car getting a good look. Unfortunately i could not see it and after the car cooled down i could not reach the leak to feel around. It looks like it is the heater core hose beacause it goes into the dash on the driver side. Not positive it is, but it is definitely in the vicinity of the other end of the hose. Just to add, this is the second time my cooling system has burst and i don't have the faintest why. I have a 13 pound radiator cap and i have heard the "waterfall" sound before if that helps. I think i should read up on the forums too because i have some nice pools of oil on my spark plugs... Thanks for any help if you have had this problem.