not sure on your car but on mine that same hose started leaking when it went below freezing a couple of times. it actually seems to be a special part in that it has a solid metal innner lining.
i think it could be replaced with normal coolant hose. the mb dealer cut me a piece (for free.. i know unbelievable but true) bacause he did not have the special part in stock.
anyhow to make a long story short i never installed it as 2 new good quality hose clamps cured the problem using the old part.

as far as i know the t-stat housing must be removed from the block in order to r&r that small length of hose.

good luck

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1984 300D Turbo - 231k....totalled 11/30/07 RIP