Your expansion tank coolant level maybe at the min mark, and when you accelerate, the sloshing cause the level to change momentarily and triggers the light. Maybe there is nothing wrong with the float switch? There really is nothing to clean other than the hinge that the arm swings on.

I am sure the Mercedes cap is a better made unit. But an aftermarket cap, as long as it fits properly, should work fine. It is not a very comples device! I do understand if you want to use a genuine Mercedes cap. My suggestion for the Autozone cap is as a diagnosis tool for the problems you are having. It certainly is a lot cheaper than a head gasket.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked