RE: Engine after run system problem

["James A. Desveaux" <desveaux@ucla.edu>]

Mike:

It's fairly easy to check out whether there's a problem with the
turbocharger coolant pump afterrun on your S4.  If you drive the car and get
it up to operating temeperature (and use the turbo a bit to accelerate the
process), and then let it idle until the rad fan comes on.  Shut the engine
off immediately and wait in the car for about 5 minutes.  THe low speed fan
should come on, and with it the turbo coolant pump.  If the fan comes on,
you can take a rag in your hand, and put it around the coolant pump to
determine if it's vibrating (pumping).  Make sure the car is good and
warm/hot when you do the test, because the thermoswitch for the coolant pump
is fairly sensitive.

If nothing happens, remove the two wires at the bottom of the thermoswitch
which screws into the bottom of the inlet water manifold under the intake
manifold.  Jump those two wires (you can also perform this test when the car
is cool).  If the fan and pump come on when you touch the wires, you've got
a bad thermoswitch (part #054-919-369B), about $30 from the dealer, or $11.
from the Parts Connection.  If the fan still doesn't come on when you touch
those two wires together, check the fuse.  On the '91 200Qs with the 3B
motor, it's fuse #21, and it should be a 25 amp fuse.  It might be the same
fuse on the S4, but I'm not sure.  When I first bought my car, I had this
problem.  Turned out the previous owner or somebody else had stuck a 10amp
fuse in there, and it was blown.  By the way, that thermoswitch is very easy
to change.  Anyway, if it's none of these things, you might have a broken
wire somewhere.

HTH

- Jim