Hoverbob

Hey all so today I decided I'd do a coolant flush and clean of the radiator just using some radiator flush stuff. I followed all the steps in the workshop manual properly and had my dad was helping me as well(I'm only 18 and this is my first car 😬)

We drained all the water that was in it (bought it from someone who appears to not have taken care of it properly) filled it back up bleed the whole system and then started my mgf to get it up to temp and to the point where the radiator fan turned on.

We let it sit running for a little bit like that just to get everything going through then I look behind me and see a huge amount of steam coming up from around the engine cover/t bar area. Turned the car off took the cover off everything's fine push the passenger seat forward and a heap of water had pooled there (was a tiny bit on the driver's side but hardly any) we then looked under the car and an absolute massive puddle of water had appeared and was dripping out of the bottom of the car.

I had a look in the center console area where the heater lines seem to run(may be wrong correct me if I am) and the water hadn't come from there, it was bone dry. So we pull back some of the carpet and the sound deading and it seems to possibly have come from around the fuel tank area but we're not sure as we didn't have a chance to get the metal plate off today to check.

We have no clue how this happened as it hasn't happened the past few times I've driven it before or anything like that(mind you I haven't used the heater) and when we opened the expansion tank after it cooled down there was absolutely no liquid left in it. Does anyone have any idea why this might have happened and what I can do about it?? Not sure if it's too important but its a 1997 mk1 vvc mgf.

Any help or ideas at all would be a huge help!!