Take the car to a radiator shop, or a shop that has equipment to test for blown head gaskets; and have them pressure test your cooling system while the motor is stopped; and again while the motor is running. If more than 5 psi pressure builds up in the cooling system within the first 3 minutes after starting the engine when it is at room temperature; there is a head gasket leak. There are also chemical tests they can do to confirm a bad head gasket. When the head gasket leaks; it usually is caused by a warped cylinder head; so the heads must be removed from the engine and checked for warpage and also tested for cracks by a competent, honest machine shop.
The initial overheating while sitting in traffic should not have happened from just a leaking water pump (unless it was pouring coolant out and the radiator level became excessively low). The usual reason such a car overheats in traffic is that the electric radiator fan is not working. This fan assembly, shown in this link: http://www.rockauto.com/catalog/moreinf
o... should be running whenever the engine becomes hot. But it is dependent on the radiator fan relay to turn it on; and those relays are known to be unreliable. If the fans do not run; replace the radiator fan relay,
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