The cooling system is pretty simple. The radiator is a
stock M3 radiator. This has 25% more cooling core than
the stock fcar radiator. I am using two 10" pullers that
are driven by the fcar PCM. There is a 16" pusher that is
driven by the BMW temperature switch.

So far so good. The pusher is set to come on at a slightly
lower temp than the pullers and so far the puller fans
have yet to even come on (except for when I disabled
the pusher as a test).

The hardest part of the cooling system was getting the
BMW gauge to work properly. The temp sensor from the
fcar won't work with the gauge in the BMW. The
resistance range is different for the fcar sensor compared
to the BMW sensor. The temp sensor is mounted into the
front of the driver side head. In the '98 fcar the temp
sensor for the computer and for the gauge are combined
into one sensor. I have heard they went to two seperate
sensors in later models. If your sensor has two wires
then you should have seperate sensors for the gauge and
the computer. If you have three wires then they are both
in the same sensor. If they are seperate then you should
be able to replace the fcar gauge sensor with the one
from the BMW. You may find the BMW sensor is an m12
and the fcar is an m10.

Since I have the combo sensor I had to use the
passenger side head to mount the sensor. In the rear of
the passenger side head the hole is there for the
temperature sensor but it has a plug in it. The hole is an
m10 and the BMW sensor is an M12. I took the plug out
and drilled and tapped the hole to an m12 and then put
the BMW sensor into this hole.

Now the gauge works perfect.
Cooling System