Your `83 300SD either has Ate, Girling or Bendix calipers
for brakes, and in various combinations front and rear
paired. From the description of the car's driving characteristics
it displays symptoms of a seized caliper or a faulty brake
line. One indication can be increased brake dust; excessive
heat another at the suspect wheel. Given the age of the
vehicle, provided the brake system has not been checked
thoroughly nor regularly serviced on time, to have a brake
caliper to disfunction should not surprise.

At or about the model year of 1983 Mercedes began to use
significantly more Bendix brand brake calipers. The chances
are good, very good, that you have combinations, in pairs,
to include Bendix brake calipers. It's not for fully certain that
you would have Bendix, just highly likely. Now there is nothing wrong with a Bendix brake.

Ate is a German brake. It works on a slightly different set
of engineering ideas than the others. Ate is well-known to
give that legendary Mercedes-like stopping power thus to
join the the other two in the class of superior brakes.

Many vendors will not rebuild brakes today. A variety of reasons
bring this about but safety, cost and liability concerns are to be
included. Therefore, if you have a seized caliper you may need to
purchase a replacement brake caliper, and in a set of pairs.

Since brakes either work perfectly or you have no brakes, I'd
see to this issue at once, and if replacement brake calipers
are to be done, too, I'd go with Ate. New brake lines are also
easy at such a time.

When one considers that brakes and steering comprise the basic
fundamentals, if one has no brakes nor steering one has no car,
essentially.