1999 BMW 328 6 cyl Two Wheel Drive
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my car is getting hot,coolent is not leaking

how hot? is the cooling fan coming on? is it boiling over?

i had replace the extended tank and i steel have the signal ,check cooling system,do this model has a termostate and where is located.?

the thermostat is in the middle front of engine. follow the upper rad hose to the housing. it all comes as one piece.

There is a coolant level sensor in the expansion tank. Did you reconnect it? Is the coolant level too low? If not, then you might need to replace it, they do fail. Repost if more help is needed.

i did reconected the sensor on the bottom of the tank ,do i need to replaced it ,the cooling level was fine

yes replace it