I have a 1985 500SEL that needs a heater core, could someone explain to me just how to take out and install a heater core in this car.

First thing you need is a shop manual...OR a W126 chassis CD from MB.

That job requires 12-14 hrs at dealer with an experienced tech & lots of tools.

ALMOST everything around the dash area must come out including the dash & complete heater box!

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