u/Disastrous_Farm3332

I replaced, or well tried to replace my waterpump today.

I checked all hoses and connections and made sure they were good, connected the union to the oil cooler and almost certain the connection is good as the holes for the screws lined up perfectly, tightened the new thermostat/pump to spec in a diagonal pattern.

Yet when assembly was done (I am a complete idiot for not testing before everything was put back in) I went to bleed the system and once the thermostat opened coolant flooded the entire garage floor.

Any idea what I could have done wrong? Any common issues with this? This is my first time replacing on a VW, and it sure as hell will be my last as well.