I just rebuilt the top end on a '86 Camaro 2.8L MPFI, it runs good, but the Temp lite comes on after 5 mins, first dim then bright, I replaced the thermostat & checked the pump. When I look in the Rad. the coolant is Not flowing, I flushed the system, all seems good.What can cause this?

 

busted water pump?

 

I pulled the pump out yesterday, it is a GM pump, all looked Ok. That's what I thought.