The stat in a benz as Kerry stated is a bypass stat.

Like a switch on a train track if it is closed the coolant circulates back into the block instead of to the radiator. Open diverts it to the radiator.

Take out the stat and the coolant can go either back to the block or to the radiator so taking the path of least resistance most of it will go back into the block so the car will run hot when it is hot outside and cool when it is cool outside.

You have to fill the system and start the car up and let it heat enough to open the stat, only then will all the coolant be released into all parts of the cooling system, ONce you get to that point you will be able to top it off most likely and get it full. It is good to check a third time though after running it for a while.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.