Changing the coolant in a 5k is a pita plus long rant

[DeWitt Harrison]

Not all that long ago, there was some discussion about the difficulty
of completely replacing the coolant in an MC engined car. I may
have missed some stuff because I turned off mail delivery during an
extended absence. Sorry if this covers old ground.

It had been observed by a q-lister that draining the old coolant per
the book, i.e. disconnecting the lower radiator hose from the thermostat
housing, did not seem to empty the system. I have just gone through the
exercise of renewing my coolant and have found it to be an exercise
in frustration. (Note: Short of pulling the thermostat itself, one way to
remove more coolant from the system is to either remove or somehow
introduce a break in the seal of the heater return hose which connects to
the
block on the engine side of the thermostat, just adjacent to the radiator
hose mentioned above. Clearly, pulling the thermostat altogether would
be the most effective method.)

[Side note: in part, the coolant change was motivated by the desire to
get away from Prestone's orange, long term' crap, which was
problematic from day one, and get back to the good old green stuff.
If the question of which is the best antifreeze is your issue, please start
a different thread. That's got nothing to do with this email.]

When I used the method described and carefully measured the volume
of coolant removed, I found that 9 pints would be released. This is out of
a total coolant volume of 18.8 pints. In other words, following the book
method apparently drains only about 54% of the total coolant volume,
leaving 46% of the old fluid or 7.7 pints of the stuff. I don't know where
the old coolant is stored but it is pretty obvious that Audi could have
designed a more efficient coolant drain point. (On my old 2002, there
was a secondary drain plug at the right-hand, lower corner of the engine
block - the lowest point in the system, duh.)

Now I assume there must be an efficient method for removing all the old
coolant but if you foolishly do as I have done and flushed by repeatedly
draining and refilling by disconnecting those hoses, you will have to go
through several cycles to do a good job. Each drain and refill cycle will
replace 54% of the coolant. If you do this "N" times, you will have reduced
the amount of remaining, old coolant by (0.46)^N. As an example, 'flushing'
twice will leave 0.46 x 0.46 = .21, or 21%, of the original fluid. To get
the
remaining old coolant percentage below 5%, you would have to repeat the
process 4 times. I've gone through 5 cycles using distilled water (2% old
stuff remaining) and I can still see the cloudy residue of the old coolant.
This brings up the old trade-off of  "total dissatisfaction" vs. "how many
hours do I devote to this?"

There must be a better way. Would someone please enlighten me?
I suppose there must be a way to stick a garden hose into an open
connection and blow all of the old shit out. (That would still leave nearly
8 pints of "garden hose water" sitting in the system as far as I can tell.
Not a great thing if you believe the only water in the system should be
distilled water.)

A related point is how to properly fill the system with the correct
mix of water and antifreeze. You can't simply poor in a 50/50 premix
of water and antifreeze because there will always be some 8 pints
of 'whatever' still sitting there. Therefore, I submit that the correct
thing to do after this sort of flushing procedure -- this assumes there
are 8 pints or more of distilled water in the system as a result of all
these flushing cycles -- is to follow the last cycle of coolant dumping
by adding the theoretically correct amount of 100% antifreeze and
then topping off with distilled water as required to bring up the coolant
level to the mark. The Bentley and the Audi owners manual both
claim that my system should contain 8.4 pints (a bit more than one
gallon) of antifreeze and 8.4 pints of water to have a 50/50 mix. So
I poured in the gallon and topped things off with distilled water as
required meaning "not much." I have not yet measured the mix with a
hygrometer but I will report the result when I have.

Meanwhile, I am just beginning to adjust to an Audi World which no
longer admits to the existence of my car. All the CIS fuel hoses any
many, many other parts where dropped from the Audi parts system in
2005. Most parts for the car are actually now NLA. So much for
Audi's support for their classic cars. (BMW, Mercedes and Porsche
all have programs specifically aimed at supporting the classic cars.
I have had no problem with replacement parts for my 1987 BMW
635CSi. Expensive? Yes. Available? Yes!!) Sadly, it's almost
time to put the old girl up on blocks behind the barn.

Go figure why I would never in a million years consider buying a new
Audi. I am constantly amazed how the corporation can decide to
blow off the older cars -- I have also observed that you poor mother
f.....ers who own '91 200s or ur S4/S6s are nearly SOL when it comes
to factory only parts such as bumper covers -- and expect repeat
business. List price for a new brake master cylinder for an Ur-S4/S6 is
well over $600. But it is STILL AVAILABLE you lucky bast..ds!
Not much else is.

Sooner or later the automotive public will become aware of  Audi's
'car-as-appliance' mentality and send the company into the same
tailspin into hell that Ford and Chrysler are now experiencing.

DeWitt Harrison
'88 5000CS