Auto Trans Fld In Cooling Sys, Red Discolouration in Exp. Tank

Automatic Transmission Fluid in Cooling System, Inside of Expansion Tank Has Red Discolouration:

Cause/Remedy:
Transmission fluid gets into the cooling system through leaking transmission oil cooler.

Replace radiator (with transmission oil cooler) Flush out cooling system.
Check coolant hoses for signs of swelling; replace, if necessary.
Check overflow tank in right wheelhouse for oil residues (red discolouration); replace, if necessary.