I have noticed that the coolant level in the radiator of my 280E (W123) always drops an inch or so below the inverted 'T' guide, no matter how often I top it up.

Once it's dropped down a little, it stays there. And there's no leak, I've checked thoroughly.

The only thing I can think of is that it might be something to do with the radiator cap, which is marked '90', although there is an original M-B sticker on the fan shroud that says a 100 cap must be used.

I'm thinking the previous owner may have substituted a 100 cap for a 90 to prevent overheating, although this has never happened to me. Could this be the cause of the drop?

Any thoughts, gentlemen?

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Chris Hunter

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1977 W123 280E auto
Cayenne Pepper orange
289,000km
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