Chrysler Repair: Leaking antifreeze and heater only works when driving fast

Question
I have a 2008 Chrysler Sebring and my car overheated. I replaced the antifreeze resivour since the mechanic said that it was the plastic washer that needed to be replaced, I replaced the whole resivour that costed me $120. After it was replaced I drove the car home (about an hour away) and the heater would not working properly. I came home and noticed again my car had no antifreeze. The next day I added antifreeze just for the car to over heat and blow antifreeze everywhere within 5 min of driving the car. During the summer I noticed that my AC was not getting very cold either. So instead of replacing every part known to man, I would like to know what I should do? I see no leaks coming from the hoses while the engine is on and parked, it seems to do it only while I drive and the heater goes from hot to cold and only heats up while I push on the gas. Can you help explain to me what might be the problem before I get charged thousands of dollars for parts I do not need to replace? I can't afford to replace all these parts while still making high payments. I appreciate your feedback, thank you for your time.

Answer
Hi Pilar,
If there are no leaks while the car is at rest and turned off, and there are no leaks either when you first start it up from cold, and then when you drive the coolant seems to be getting lost (again with no signs of a frank leak up front until it overheats and then boils over) then I would suspect that there is an internal leak of coolant from the cooling system passageways inside of the engine that passes coolant into the combustion chamber of one or more of the cylinders. When that happens the coolant is expelled from the chamber with the exhaust gas and comes out the tailpipe as white smoke that has the odor of antifreeze. So see if that is not the case when you first start it up from cold.
Were that the case then that usually means that the gasket between the cylinder block and the head of the engine is leaking. This is called a "blown head gasket". There are a couple of things to try before removing the head and replacing the gasket which is a fairly costly repair job. One thing would be to loosen the bolts on the head about 1 turn, then retighten all the bolts in the manner suggested in the manual to the specified torque setting. A shop could try that for maybe an hour of labor or so. The leak could be due to one or more of the head bolts being too loose.
The other thing to try would be to put some cooling system stop leak in the system following the instructions on the container and see if that seals up the leak. A good brand is called "Bar's Leak" if you want to try that.
Otherwise you have to remove the head and put in a new gasket which requires more labor time than either of these other things to try first.
Let me know if you do see whice smoke coming out the exhaust pipe, and tell me which size (L)engine you have in the vehicle.
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Roland