Diagnosing an overheating 2001 malibu

my 2001 Chevy Malibu overheatedon the freeway the other day. I bought hey thermostat but I don’t know if it is the water pump or not. Is there any way to tell without going through the elimination process?

Why do you feel the problem is limited to either a thermostat or water pump ?

@ChristianPhillips you already bought the thermostat.

Install it, along with a new cap, and see what happens.

Are the fans coming on?

Intake manifold gaskets commonly leak on your car. Do you see any leaks? Look in the coolant reservoir. See any oil in there? Pull out the dipstick. Does it look like oil? Or does it look like coffee?