Sounds like you could use a new water pump, if I remember correctly it seals with an O ring and not a gasket. When I bought my 240D that was about the first thing I did, replace the thermostat & water pump. I was having a lot of warm then cool periods when driving the car, no more since thermostat & waterpump replacement.

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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.