ok, guys ... sorry to be so long, but i had misplaced james' procedure for
flushing the coolant in a water-cooled vw.  i had to retype it. :(  so here
it is (james, if i got it wrong, let us all know ... otherwise it goes in the
FAQ as is). :)

Useful Tricks when changing the Coolant (1983.5-1991 models only)
<jamesl@galaxy.nsc.com>

1.  Remove the spare tire.
2.  Loosen the radiator support screws (4 of them) so that the
    radiator bleeder screw is easier to work with.
3.  Choose one of the two hoses running between the front and rear
    heater cores, and cut it at a location close to the front of the
    car.  Install a "flush Tee" (available in most auto parts stores),
    and connect a garden hose to this Tee.
4.  In the Bentley manual, the drain plug under the engine is removed
    to allow the coolant to drain.  This is NOT very pleasant and the
    draining is NOT easy to do this way.  Just remove the two big hoses
    connected to the engine block ... much easier.
5.  There are two large hoses connected to the left side of the engine
    block.  Disconnect one of them, turn on the garden hose (see #3)
    for two minutes, then re-connect this hose.  Disconnect the other
    large hose, and run the garden hose for another two minutes.  Turn
    off the water, disconnect BOTH hoses, and let the water run out of
    both hoses.  Reconnect both hoses to the engine block.
6.  Remove the garden hose and put the cap on the Tee ... tightly.
7.  There is about two gallons of water left in the system now.
8.  Follow the Bentley manual and refill the system with about 2.25
    gallons of 100 percent coolant/anti-freeze.

I do this once a year to eliminate any air in the system.  This is
cheaper than a $1000 headgasket job from engine overheating, due to
air in the system.