Block in the radiator?

I opened my radiator cap yesterday and found there was a ton of nasty brownish sludge in it. The radiator was recored last year. I have only driven it a few hundred miles sense last year and it was sitting for about 5 years before that. The odd part was my temp gauge and gas gauge dont work, so i was replacing my temperature sensor. When i pulled the old one off bring green coolant started squirting out. Is it possible that the coolant isnt circulating properly? the Thermostat and water pump have both been replaced along with the recored rad. Thanks for any help guys!

Also any idea on those gauges would be cool too. both gauges are flat even with the new sensor on the temp.