Car overheats on freeway

Two things to check:

1. Make sure you do not have an air bubble in your cooling system. Easiest way is to park facing uphill and let the car cool off. Remove the radiator cap, start the car and let run until the thermostat opens. If there are air bubbles in the cooling system the should be forced out. Top off fluid.
2. Are you sure that the cooling fan is running? When the car is getting hot, open the hood and make sure the radiator fan is actually turning.

your heater core is blocked

It is more than likely your water pump. Can you run it in park with the radiator cap off. The cap on the radiator not the overflow tank. When the temp opens the thermostat you should see flow if the pump is good no flow it is probably bad. If you don't see flow check the upper hose for temp and the lower hose. If the upper line is barely warm and the lower hose is significantly hotter, it is either water pump or thermostat, but since you replaced the thermostat I would be back to water pump. BTW you should use either a contact thermometer or an infrared to check hoses, although it was done by hand in the old days.

If your car is overheating when you drive it,but you have replaced and made sure the radiator fan motor is working and coming on,you have flushed the system and replaced all your cooling components,then you may have a blown head gasket.Check for a milky white look to your oil dipstick.If so,you have a blown head gasket.or you might also have an air pocket in your cooling system that you need to bleed out.Good luck.

Classic signs of a bad water pump. When on the freeway, the circulation of coolant through the system is increased due to the speed but once you slow down, it will tend to overheat. Please post back with any other questions or just to rate the solution. Thanks very much!
Greg

if it overheats at freeway speed, its a dirty radiator(flushing it usually don't help but you can try) If it overheats it traffic, then it is the automatic radiator fan(usually driven by electric motor). On some ocation an overheating is caused by retarded timing, but very unlikely on your vehicle since it is computerized.

Unfortunately, I refer to repairs of this type as "search and repair missions"...You've overlooked the radiator core...the only thing left and probably the culprit. ($180)
Good Luck

If you haven't flushed your radiator, i would recommend this asap. i would also inspect the water pump and thermostat as well. replace both components if found to be faulty.

Make sure the cooling fan is operational. it should cycle on and off if the air condition is activate.

check the casting on your replacement water pump..4.0l engines require a reverse rotating water pump..may be causing your problem.

CHECK SOME BASIC PARTS, THE THERMOSTAT AND YOUR WATER PUMP, THE THERMOSTAT MAY BE THE WRONG DEGREES OR THE WATER PUMP IS GETTING A TIRED YOU JUST HAVE TO FIGUERE OUT WHICH ONE. IS THE PROBLEM...
CHEERS..