Zhang wrote: < When I tried to unscrew the nut > which hold the steel line
into the radiator, the coolant came out.>
If coolant came out of the loosened connection on the heat exchanger, then
either you are undoing a wrong connection ? or there is a problem with the
heat exchanger. Disconnection the transmission fluid line should not
release coolant, unless the transmission is full or partly full of coolant
Apart from following Brett’s advice in relation to the gradual renewal of
transmission fluid, can you clarify that coolant has not entered the fluid.
I think that this is not unknown, but is generally confined to the later
X300 models ???
With regard to your electric brake motor / pump problem, from your
descriptions it is amazing that the motor is operating in any fashion. It
may well be drawing more current than it should. Is it protected by a fuse
of the original size ? If it is on an unprotected circuit or has a fuse of
larger size in the circuit, you may do other damage, e.g. to the wiring
loom, fuse holders etc.