Coolant woes

[antny]

So this past week I did a water pump and a 160 thermostat swap. After the swap I was able to pull vacuum with a uview and filled the system back using Porsche coolant. Car seemed fine and took it around the block to see if there was any air pockets. About a block away from the house the temp started to rise and I was able to make it home within a minute later. I look in my driveway and there is a puddle of coolant and trail of coolant down my street. The leaking is coming from the right rear tire area. That I would assume is my yellowish expansion tank took a dump on me. I was able to fill the system back up at 22 PSI of vacuum. I started the car back up t see if it was going to get hotter than 180. It did not climb but the temperature light started to flash. I turned the car off immediately and checked to see if there were anymore leaks from the expansion tank area which there were not.

I already ordered a new expansion tank but with it not leaking again and the temp light flashing what else could it be???

Thanks all.