Translucent hose is the vacuum pump exhaust air hose.
It is just a vent for air from the vacuum pump that goes to your air filter.

The dried coolant on the translucent vacuum pump vent hose, radiator hoses,and radiator is most probably from leakage of coolant from the top radiator hose when the system is pressurized.

The MB rubber hoses remain quite pliable for an amazingly long time.
The top radiator hose may be long enough to allow you to trim an inch off the hardened hose end, reattach the trimmed hose to the top radiator nipple, and get a better seal.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022