When I drained the system I opened the petcock on the drivers side
"THE" petcock? On the driver's side of WHAT?
Guessing it's on the driver's side of the radiator.
It's silly to "flush" a cooling system and not drain both banks of the V-type engine (V8, V6). There's a gallon or more of flush water still trapped in the block when the radiator is empty. As said, the knock sensor ahead of the starter motor on the passenger side is the block drain (it goes back in with sealer on the threads, and a specific torque spec.) There's an iron or steel hex-head (9/16 wrenching surface) plug on the driver's side. Again, sealer on the threads and a torque spec. It's common to pull one or both plugs out and get no coolant draining, because there's so much sediment at the bottom of the water jacket that you have to poke a screwdriver or awl through the "crust" to get to water.
Probably also means that the antifreeze protection is crap--antifreeze too diluted. Which means you still need to pull the block drains, and basically start over with the coolant refill. Always pour the correct amount of antifreeze into the engine (saving enough for the overflow bottle) BEFORE adding water.
"Road salt" means NOTHING when it comes to the cooling system, except for potential corrosion of the radiator air fins.
there was no thermostat in the motor. I have since installed one once I started to fill it up
You should pull the 180 'stat back out, and install a proper 195. The computer programming along with the clutch fan are designed for 195--200 degree engine operation.