Looks like the level is moving around 1.5 to 2 inches on the side of the expansion tank.

Seems like if it was supposed to move this much the owners manual would have said something like "only check the coolant level with the car off" or they would have two lines marked on the tank.

It is like the coolant is taking a little trip somewhere else while the engine is running at higher rpm's and then returning to the tank while idling or off?

I am confused. Where is it going?

Thanks,

Clay

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2002 E320 Sedan 93K Designo Mocha Black Metallic!
1995 E320 Wagon 205K Black Wagon
1982 240D 183K SloPoke

I believe each of these cars are the final production year for that model.