overheating and air in coolant system on 2002 Chrysler Sebring

my car has been overheating and I had the thermostat replace as well as the coolant system sensor but it is still overheating.The first mechanic that replaced the thermostat said that air keeps getting into the coolant system and I would need to replace the water pump then told me it was gonna be $400.00 which at this time I just can't afford. The second mechanic that took a look at it notice that the coolant system sensor needed to be replace so that was done then took a look at the radiator which was cooler towards the bottom of the radiator and hotter towards the top of it. Will this take care of my overheating problems?

by in Carol Stream, IL on August 19, 2010
2 answers
ANSWER by , August 19, 2010
A radiator is supposed to get cooler from the top down, because the hot water enters the top of the radiator and then as it makes its way down to the bottom, the air flow cools the water or coolant. really need to a few things: 1. do the cooling fans work properly? turn on the A/C , they should come right on. 2. is the coolant circulating through the radiator or is it plugged up? 3. Does the water pump push the coolant through the engine fast enough? 4. Is the new thermostat working properly, can you feel it open when the engine gets hot, you can easily test this by letting the engine warm up and the bottom hose will be cool at first, then as the thermostat opens, the bottom hose will get hotter and hotter, this MUST happen.
ANSWER by , November 18, 2010
there is another thing that the 1st answer didt telll you. you could have a problem with ur head gasket. some time the go bad in a way that lets combustion air that the motor makes and pushes it in to the coolant system