Brake dragging?

[Scott Dudevoir]

About every couple of years my '85 5000S develops the following
recurrent symptoms:

Starts with a grinding rubbing sound from the front wheel area timed
with wheel rotation, the car bogs down, mileage drops considerably, the
wheels can get untouchable hot from the extra friction, excess brake
dust builds on the wheels.

My assessment is the front disc brakes are getting hung up and dragging
 on the rotors.

I have tried a number of repairs to eliminate: system bleed, caliper
rebuild, master cylinder replacement.
Thoroughly cleaning all the contact surfaces has seemed to help the most
in the past, BUT NOT ALWAYS.

Has anyone else had similar problems?
Any other possible causes of symptoms?
What conditions might aggravate this?
Solutions?
When cleaning the calipers and carrier brackets, any specific
recommendations, lubricants?

Thanks,
--Scott Dudevoir