'Brown' is not a color you should see in the coolant, no matter which type is used. MB coolant is very light yellow - appears colorless in the system. Brown means oil, from a blown head gasket, usually, and will mostly float as crud on top in the reservoir. That reservoir has a 'low level' light, which is probably what is lighting on the dash. If the hoses are 'sweating', then they are ripe for failure and should ALL be replaced too.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7