Radiator Efficiency [WAS: Audi 200 voltage]

[urq]

I too am dealing with a cooling system issue on the 83 urQ with MC-2 block
and MAC-02 control/FI.

The problem appeared to develop all of a sudden, but it may have correlated
with the warmer season.  I replaced the thermostat, with no change in
symptom.  I suspected a possible combustion chamber leak, but compression in
all cylinders is good and all spark plug ground electrodes have a nice,
consistent tan color.  I have even tried a different radiator ... one
removed from an urQ a long time ago and sitting on the shelf.  This last
report is a recent development and I have not taken the car out for a long
enough drive to see if the VDO temp gauge pegs ... I'm thinking the rad
replacement may have improved the situation.  I also find that running the
interior heater at full hot with the blower on high seems to bring the
coolant temp down a bit.  I'm pretty sure the water pump is working as
everything in the cooling system gets evenly hot.  My car still has the
factory motor with 3 blade fan, as far as I can tell the fan is operating as
it was intended.  

My main question was ... does anyone have any empirical or anecdotal
information on the temperature difference one should expect to see from the
inlet of the radiator to the output?  I was thinking about poking a
thermocouple into the upper and lower lines and seeing how much difference
there is.  

This problem is limiting my use of the car, and I'd like to get everything
sorted before the UPG events in a couple weeks, so I will certainly
appreciate any info I can get on nailing this one.  I have to admit that
since I'm seeing that the problem is not likely to be the head gasket that
I'm tempted to pull out the wallet and get one of the units Javad offers ...


TIA!
Steve Buchholz

-----Original Message-----

What I'm getting at is that it may be time for a new radiator; the
less efficient the radiator, the more time the fan runs.  Is it
original? How many miles?  Do you use the blue stuff, or the green
stuff?  Lot of bugs and sand/dirt where you drive?  Might be worth
popping the top plastic cover off and eyeballing the AC condenser,
where all that crap gets embedded :)