Engine Cooling problem
1998 Oldsmobile Aurora V8 Front Wheel Drive Automatic 126000 miles
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my 98 oldsmobile aurora keeps overheating while driving around town or just idling. i have changed the thermostat and flushed the radiator. my mechanic says the water pump is fine and there are no visable leaks. a shop says its an internal combustion to coolant system leak that cannot be fixed, but i read that it could be a bleeder valve not opening causing heat to be trapped under the thermostat. This is my only car and i am a single mother...can someone please help or share their opinions and experiences. Thanks!

Have the shop to pressure test the cooling system. They can find leave the pressure on this system for a long as necessary to find the leak. Also, internal combustion leaks can be verified by using an exhaust analyzer to "sniff" combustion gases that may be present in the cooling system (i.e., radiator). Finally, when coolant leaks it usually leaves streaks. Although the engine block and heads may be dry they should look for these streaks (especially where the water pump passage(s) bolt to the engine).