If you're water pump was going....it would leak or have a broken impeller shaft :lol:
If you really want to test the water pump, start the engine with the thermostat out and upper hose unhooked from the radiator, then rev the engine...you'll see instantly if it's working ;)
Overheating at speed is a flow problem. How long will it idle before it overheats? Mine used to do that, overheat at speed ( hwy driving ) and normal operating temps at long idle in traffic ( 15-20 min of idling )
It ended up being a plugged up radiator...and it just started doing it one random day, it wasn't a progressively worsening condition.
http://www.forabodiesonly.com/mopar/showthread.php?t=43837
After digging into the radiator I made several hwy trips of 3 hrs or more and it never got above the second left temp mark, even at 75-80 mph with the A/C on
You could always get one of those little dentist mirrors and have a look inside the radiator, but my money is on a bunch of plugged passages...
