was told the thermostat was bad. i replaced it and it still heats up. upper hose is hot while lower is cooler and engine gauge reads hot and the radiator fan will not come on even when th a/c is switched on and the heater blows cold.
overheat on 2000 BMW 328i
Check to see the radiator is circulating the coolant efficiently, no cold spots which would indicate a plugged up radiator core, check no air is trapped in the coolant system if so purge air from the system, check that the head gasket is not mildly blown , a test called a block check is good to test for carbon monoxide in the cooling system, Finally ensure the water pump is circulating coolant properly. Some BMW's use a non metal water pump impeller that fails.
we have the same problem with our 2000 BMW 328I. The fan should kick on as soon as the A/C engages. Yet no matter what, the fan never engages. Where is the switch that engages the fan when the A/c comes on and is there a wiring diagram for this system? Fuses all good.