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RE: NEED OIL COOLED TURBO! (actually, I just learned that it's air cooled)

At 09:50 AM 11/4/98 -0800, you wrote:
>The reason the newer turbos use an auxiliary water cooling system to cool
>the turbo bearings after the engine is shut down is likely to be that it is
>much easier to plumb an auxiliary electrical water pump into the cooling
>system than an auxiliary oil pump ... especially given the fact that the
>water cooling ports on the turbo are added from the basic turbo ... which
>makes me wonder how much water is flowing through the turbo bearing jacket
>while the engine is running?  It could actually only be "used" when the
>engine is shut off ... I don't know about this one way or the other as it
>just came to mind ... I guess I'll have to look at the plumbing to see ...
>Steve Buchholz
>San Jose, CA (USA)

Hi Steve,

The 1985 model change info booklet I've got describes the "new" water
cooled turbo in some detail.  Seems the water flow during engine operation
is opposite to afterrun.  In other words, flow comes out from the port on
the freeze plug, runs upwards thru the turbo and back into the radiator via
the upper coolant hose.  On afterrun, the aux pump takes its input from the
rigid pipe back into the thermostat housing and pumps into the tap on the
upper radiator hose, circulating coolant thru both the radiator and back
down into the turbo housing.


Tony Lum                                  1987 5000CS Turbo Quattro
Berkeley, California, U.S.A.                1985 4000CS Quattro
Audi Owner/Driver/Mechanic by Necessity ;^)   1980 5000S Sedan
                                               1987.5 Coupe GT