I am stumped on this one. I did do a search but found no answer.

I have owned three W124 cars and they all use the metal coolant expansion tank caps.

My 1997 E320 uses a screw on plastic cap.

Now my 2003 E320 wagon (also W210) uses a metal coolant expansion tank cap similar to the ones on W124. You push in and turn 90 degrees. However, all online catalogs call for a plastic cap just like the one I have on the 1997 E320.

What could have happened here? The coolant expansion tank and cap were not original on my 2003 E320 wagon or the catalogs are in accurate?

Thanks,