My 96 Deville keeps overheating.. I've tested the heads for leaks.. passed. changed the tstat twice. put new radiator hoses. flushed the radiator and the engine. This has been over the corse of 3 weeks. everytime i change a part or add new fluid she runs fine for two days an then will not cool down. fans work properly, no leaks. When it runs hot the hoses are full af fluid and tight as if there is no circulation hense the change of the tstat.. like i said, ran fine for 2 days and did the same thing. tried flushing the system thinking there was a clog but again, after i was done she ran fine for a day and a half an overheated again. Tomorrow I'm suppose to change the water pump?? Any advise before i start this procedure? Pls? Jay.. bka.. rotwyla. thanks in advance.