Why is my chrystler seabring over heating and I changed the water housing and thermostate?

Light is on when push down.Mast be something wrong.

Check to see if your fan is coming on. if it is then check the middle of your radiator if it is cool while the outside is hot you have plugged radiator

have you checked / changed radiator? check for water flow?

Make sure the fans are coming on or it will over heat. If the fans come and the gauge is reading hot check the thermostat. Follow the top radiator hose to the engine block it probably has 2 bolts holding the thermostat housing on.

The water pump has what's called a 'weeping hole' built into it. If the pump is bad You'll se water coming out of the hole. When was the last time you flushed the radiator? It may be your radiator cap is bad, they should be changed once a year & the radiator flushed. You can also test ur thermostate. take out ur thermostate & put it in a pot of water so that the water covers the thermostate. Then put a cooking thermometer in the pot to & heat the water til it says 195. u should see the car thermostate begin to open. if it don't it's bad & needs replacing.

CHECK WATER LEVEL CHECK OIL LEVEL IF NO WATER FILL UP AND IF WATER DISSAPERS OR TURNS MILKY YOU HAVE A HEAD GASKET PROB CHECK WHILE RUNNING BUT DONT GET TOO HOT

Take it to another shop, The water pump doen't hold the Thermostate. The thermostate is in the thermostate housing where the end of the radiator hose is connected to the egine. 
There are different thermostate rating to which temprature you'll like your engine running at. Most common would be a 190 thermostate you can get them from 160 up to 220. 
As for the water pump you would know if that failed do to over heating or leaking from the weep holes in it. 
Bring the truck to another shop and have them flush and Antifreeze if it's never benn done and change the Thermostate to a 180 or 190 and should be done every Two years do to waer and tear. Note the 180 runs cooler then the 190 and so on. 
I run mine on 160 since I tow a trailer and the radiator also cools the transmisson oil too. Just for though but you should be fine at 180 or 190.
Good luck and hope this helps.

make sure engine is cool then drain coolant by opening the drain plug at bottom of radiator. remove cap from radiator so coolant will continue to drain and when coolant is down enough to pull off upper radiator hose at intake then close drain, then remove two bolts at coolant housing and remove thermostate. clean gasket material from intake and housing and replace with new gasket and thermostate tighten bolts install hose fill rad with coolant water mix 50/50 and run engine with heat on floor until gets hot and you see coolant flowing in rad, install cap

follow the hose from the radiator to the housing and inside the part the hose conects to will be the thermostate just be sure you pay attention to how it went in, if you live somewhere warm you dont even need it in there, it just helps heat the car before opening and flowing to the heater core to give the interior heat. usually its the upper radiator hose that you follow, good luck if you need a more specific guide i can look it up in mitchelondemand5 for you, thanks and pass the blue please ; )
Erik
ez automotive/U.S. Army

your thermostate is probably on the block sideways in whitch case you need to remove the air filter outr of your way and loosen the clamp on the thermostate housing. from there take out the 3 bolts holding the thermostat housing in place and remove it. Caution water/antifreeze will come out. take the thermostate out watching where the gasket has been placed and install the new one after cleaning the suface of the old gasket. sometimes it is good to use indian head gasket sealer. there will be 2 bolts on top and 1 bolt on the bottom under the housing. install the new thermostate tightn the hose replace your filter and fill the over flow resivor only to the point on COLD MAX. take the cap off the radiator start the car wait for the thermostate to open and fill the raditor the rest the way up. if it starts to boil over just shut the car off and let it cool than add more water *** needed...