bmw 540i 1999 smoke was coming out of the resevoir tank cooling cap

I have a bmw 540i 1999 smoke was coming out of the resevoir tank cooling cap which lets the evaporation seep out it was coming out of that. do I replace the tank or is it a thermostat if so where is the thermostat located? thanks

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW 3-Series E36 Cooling System Flush

[Nick at Pelican Parts]

The thermostat is located at the front of your engine, above the water pump.

Check that your engine isn't overhating, smoke should not be coming outof the reservoir.

- Nick