Ford Repair: cooling system not working properly, ford f 150, rust color

Question
1992 Ford F-150,302 v-8,a-c,92K miles; just put in new plugs, plugwires, rotor and cap and fuel filter, thermostat,air filter, changed oil and oil filter about 2 months ago. Started running poorly about a week or so ago. Checked out fluids,oil dirty, changed it and filter, checked coolant and it was a nasty rust color. Flushed radiator, refilled let run for awile doesnt seem to be flowing threw at all.

Answer
The water pump is probably bad.  The impeller may have rusted out and is not pumping the coolant through the cooling system.  If there is no coolant flow, the engine will run hot and overheat.  Running hot will make the engine run rough, lack power, and cause spark knock.  Overheating can damage the engine.  The temperature sensor can read incorrectly if there is no coolant flow because there may be pockets of hot and cool coolant, and the temperature can't equalize.  The same is true if air is trapped in the system.  The engine oil can normally look black and dirty very soon after an oil change.  This engine is known for sludging the oil, and it should be changed religiously.

I hope this helps,
Dave