Several years ago I needed a new radiator cap for my 240. I ordered one and it was a higher pressure than the origional. I believe it was a 1.2ATM. That was all that was supplied. The parts place called a friend in the business and he gave them a BMW part number that was for a BMW 1600-2002 model. It is for a 1.0ATM cap...same manufacture as the MBZ cap.
I needed to buy another for a clients car this last week and thought I would post the part number incase anyone needs it.

BMW part number...1711-1-100-848

Especially because our cars are 20 to 25 years old, I don't want a higher pressure cap straining the older heater cores, hoses, radiators.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.