W123, 300SD

MY 1983 Mercedes 300CD TurboDiesel AC produces no air flow at the vent. I have rebuilt the motor, new brushes and it works beautifully. I tried reversing the wiring at the plug under the dash and that produced less pressure. I measured the flow by taking the motor fan out of its housing and turning in on and it is still fine and produces a good
fan noise when in the housing.
Next I checked all the vents and only the center vent needed a connection. Now they all work and work correctly according to the the CC control sequence. All tested well.
Still no flow at the vent only a whisper of air.

What sort of radiator coolant should I put in my '84 280E (W123)? I've recently acquired this car, and the previous owner reckons he had the system flushed and the coolant replaced not long before selling (but he did not keep the receipt for the work). The system certainly seems full of clean, bright green fluid but I have no idea what brand/type of coolant it is. Should I be looking to flush this coolant out of the system and replace it with coolant supplied by a Mercedes Benz dealer? Thanks in advance.

Brad

For about a year I've noticed a clunking noise/vibration in the right rear at sustained highway speeds after about 45 min. Almost sounds as if I dropped my muffler and the pipe is banging and dragging , and there's a noticeable squeeking or high pitched rubbing sound as well. New Tires and shocks, new brakes & pads ,new muffler, all donuts OK . Noticed a worn center drive shaft carrier and one cracked CV boot. Flex joints checked out OK.

Noise doesn't happen in normal driving around town. 2 mechanics have thus far been unable to diagnose.

Have any ideas?

While working on my vacuum system I ran this car in my garage for several minutes. I noticed an oily residue on the garage floor. Anything to be concerned about? Thanks.